Influence of ocular biometry on peripheral retinal visualization: A comparative study of Clarus and Optos widefield imaging systems

Influence of ocular biometry on peripheral retinal visualization: A comparative study of Clarus and Optos widefield imaging systems | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Influence of ocular biometry on peripheral retinal visualization: A comparative study of Clarus and Optos widefield imaging systems Christoph Spartalis, Andreea Fisus, Manuel Ruiss, Oliver Findl This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8369016/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 11 Apr, 2026 Read the published version in BMC Ophthalmology → Version 1 posted 12 You are reading this latest preprint version Abstract Background The purpose was to compare the Clarus 500 and Optos Daytona widefield imaging systems with respect to the farthest clinically assessable peripheral retinal structure in each quadrant, and to evaluate whether ocular biometry, particularly axial length and spherical equivalent, influences device specific widefield performance. Methods Twenty-six eyes underwent same day widefield imaging with Clarus 500 (Zeiss Meditec AG, Jena, Germany) and Optos Daytona (Optos plc, Dunfermline, UK). For each quadrant, the most peripheral anatomically interpretable structure was identified, and device differences were analyzed using McNemar tests. Associations with axial length and spherical equivalent, were evaluated using Mann-Whitney U tests and univariate and multivariate logistic regression. Receiver operating characteristic analysis was performed to assess the predictive value of axial length and to determine the optimal cutoff for device superiority. Results Both widefield systems showed similar performance in the superior temporal, inferior temporal, and inferior nasal quadrants with no statistically significant differences. In the superior nasal quadrant, however, eyes in which Clarus reached farther had significantly longer axial length (23.97 ± 1.62 mm versus 22.53 ± 0.94 mm, p = 0.016) and a more myopic spherical equivalent (− 2.05 ± 4.52 D versus + 2.69 ± 2.56 D, p = 0.019). Axial length significantly predicted Clarus superiority in univariate regression (odds ratio 2.39, p = 0.033). Receiver operating characteristic analysis demonstrated good discriminatory ability of axial length with an area under the curve of 0.782 and an optimal cutoff of 23.77 mm. Shorter and hyperopic eyes showed a tendency toward greater peripheral reach with Optos, although this trend did not achieve statistical significance. Conclusion The Clarus 500 and Optos Daytona provide comparable peripheral visualization in most retinal quadrants. Device differences become apparent in the superior nasal quadrant, where axial elongation and myopic ocular geometry enhance Clarus performance, while no statistically supported advantage for Optos is observed in shorter or hyperopic eyes. These findings underscore the relevance of ocular biometry in widefield retinal imaging and support individualized device selection in patients with myopic anatomy. Overall, both devices demonstrated robust and reliable performance, providing high quality widefield imaging suitable for comprehensive peripheral retinal assessment. Ultra-widefield imaging Peripheral retina Ocular biometry Axial length Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Ultra-widefield (UWF) retinal imaging has transformed modern ophthalmic diagnostics by enabling clinicians to examine the peripheral retina far beyond the coverage of conventional fundus photography. Standard cameras typically visualize only a limited portion of the posterior pole, which leaves large areas of the mid-periphery and far periphery unassessed. This becomes clinically relevant because numerous retinal abnormalities arise preferentially in these regions. Conditions such as lattice degeneration, white without pressure, cobblestone degeneration, peripheral pigment alterations and asymptomatic retinal breaks may influence the risk of rhegmatogenous retinal detachment or guide management strategies in patients with peripheral retinal disease [ 1 – 3 ]. Consequently, the ability to reliably determine the most distant clinically interpretable peripheral point in each quadrant is essential for accurate screening, risk stratification and longitudinal patient care. This is particularly relevant in settings where subtle peripheral pathology may precede sight-threatening events, such as the use of widefield imaging to screen for early retinal detachment in eyes undergoing intravitreal injection. UWF imaging systems were developed to address the limitations of conventional photography by expanding the field of view and offering a more comprehensive visualization of retinal anatomy. Among these systems, the Zeiss Clarus 500 and the Optos Daytona have gained particular prominence in routine clinical practice. Although both are considered widefield imaging platforms, they are based on fundamentally different optical concepts. The Clarus 500 uses a design that relies on partially confocal imaging and broad-spectrum RGB illumination to produce true-color images with reduced peripheral distortion [ 4 – 6 ]. A single image provides a field of approximately 133 degrees, and two sequential captures can be combined into a montage that reaches a field comparable to that of the Optos system. This approach results in more anatomically realistic contours, improved color representation and fewer eyelash artifacts. At the same time, the use of a montage and the need for stable fixation may introduce practical limitations when attempting to visualize the most extreme periphery [ 7 ]. Alternative, the Optos Daytona acquires a nominal 200-degree retinal field through a single dual-wavelength scanning laser exposure supported by an ellipsoidal mirror configuration that allows imaging without pharmacologic dilation [ 8 ]. This enables rapid acquisition and extensive field coverage. However, the geometry inherent to the scanning and projection process creates nonuniform peripheral magnification and peripheral stretching, especially toward the far temporal and nasal regions, which may modify the appearance of the extreme periphery and influence the visibility of subtle anatomical details [ 9 ]. Comparative investigations across various UWF platforms have shown that differences in illumination, optical geometry, confocality and image processing directly affect peripheral visibility. Studies in diabetic retinopathy have demonstrated that both the Clarus and Optos systems offer reliable lesion detection but differ in the balance between field extent, color rendering and susceptibility to artifacts [ 6 , 10 ]. Additional research comparing field size and the distribution of clinically relevant features has emphasized that the nominal field of view alone does not adequately describe the functional extent of the clinically interpretable image. Instead, factors such as local retinal curvature, edge distortion patterns and illumination uniformity play a major role in determining how far into the periphery meaningful diagnostic information can be obtained [ 11 , 12 ]. Despite the widespread use of these technologies, limited work has focused on the precise quantification of the farthest clinically interpretable peripheral point in each quadrant. Many earlier studies assessed overall field size, global image quality or the presence of specific peripheral lesions, but they did not evaluate the actual anatomical limit up to which structures remain interpretable. This limitation is clinically relevant because UWF imaging demonstrates only moderate sensitivity but high specificity for detecting treatment-requiring retinal tears and holes, even when interrater agreement is high [ 13 ]. Consequently, the clinically assessable retinal boundary cannot be inferred from nominal field specifications alone; it reflects the combined influence of optical design, projection geometry, patient-specific anatomical factors and the interaction between the imaging beam and the peripheral globe contour. An additional factor that may affect peripheral visualization is ocular biometry, particularly axial length and refractive state. Eyes with long axial length typically display differences in retinal curvature, posterior contour and peripheral shape compared with eyes of shorter axial length. These anatomical variations can influence the interaction between UWF imaging beams and the retinal surface and may alter the effective peripheral visibility achieved by different imaging systems [ 14 , 15 ]. Although Clarus performance has been investigated in cohorts with medium to high myopia [ 16 ], the combined evaluation of biometric influences in direct comparisons between Clarus and Optos remains limited in the existing literature and therefore represents a meaningful area of investigation. The aim of the present study is to compare the Clarus 500 and Optos Daytona with respect to their ability to visualize the farthest clinically assessable peripheral point in the four standard retinal quadrants. The study further examines the relationship between peripheral visibility and ocular biometry, including axial length and spherical equivalent. By focusing on the clinically interpretable boundary rather than nominal field specifications, this investigation provides a functional assessment of peripheral visualization and contributes to a more comprehensive understanding of how device design and ocular anatomy interact in UWF retinal imaging. Methods This prospective paired comparative imaging study was approved by the institutional ethics committee (EK19-207-0919), registered at clinicaltrials.gov (NCT04255732) and conducted in accordance with the declaration of Helsinki. Twenty-six eyes from 30 adult participants were enrolled. Written informed consent was obtained from all subjects before participation. All individuals underwent same-day non-dilated UWF imaging with both the Clarus 500 (Carl Zeiss Meditec, Jena, Germany) and the Optos Daytona (Optos plc, Dunfermline, UK). To minimize potential order effects related to accommodation, fixation stability or tear-film variability, the sequence of device imaging was randomized for each participant using an online randomization tool (Randomizer, www.randomizer.org ). Eligibility required clear ocular media suitable for widefield imaging, stable fixation and the successful acquisition of clinically interpretable images on both devices. To ensure that lens opacities did not impair the ability to evaluate the far periphery, all participants underwent a standardized cataract assessment using the Lens Opacities Classification System III (LOCS III) [ 17 ]. Eyes with dense cataracts were excluded. Further exclusion criteria included any history of retinal detachment, previous vitreoretinal surgery, dense media opacities, poor fixation or insufficient image quality due to blinking or motion artifacts. Axial length was measured using the IOLMaster 700 (Carl Zeiss Meditec AG, Jena, Germany), a swept-source optical biometer equipped with multidot keratometry. Refractive data were assessed with subjective refraction and noted as sphere and cylinder, and the spherical equivalent was calculated as sphere plus half of the cylindrical power. The Clarus 500 (Carl Zeiss Meditec AG, Jena, Germany) uses partially confocal true-color imaging with broad-spectrum RGB illumination and produces anatomically faithful images with reduced peripheral distortion. A single acquisition covers approximately 133 degrees and can be extended through a two-image montage. The Optos Daytona (Optos plc, Dunfermline, UK) employs dual-wavelength scanning laser illumination at 532 nanometers and 633 nanometers combined with an ellipsoidal mirror, allowing a nominal field of approximately 200 degrees in a single nonmydriatic capture. Peripheral regions of the Daytona images frequently show characteristic stretching and nonuniform magnification. All imaging was performed by the same experienced operator, and the sequence of device acquisition was randomized to reduce the influence of accommodation, tear-film variability and fixation fatigue. The primary study outcome was the farthest clinically assessable peripheral point in each of the four quadrants. This point was defined as the most peripheral retinal structure that remained clearly visible and diagnostically interpretable. Acceptable structures included peripheral vascular branches, pigmentary alterations and lattice degeneration. Peripheral areas in which the image boundary was visible, but no structure could be confidently recognized were not considered clinically assessable. One masked retina specialist independently reviewed all images and was unaware of the imaging sequence and biometric measurements. All peripheral structures and measurement endpoints were evaluated using ImageJ (Version 2.0.0 rc43/125n) ensuring standardized and reproducible image assessment. For each quadrant, visibility was categorized as Clarus further, Optos further, or equal. Associations between device performance and biometric parameters including axial length, spherical equivalent and age were examined. Statistical analyses were conducted using IBM SPSS Statistics Version 29.0.0.0 (IBM Corp., Armonk, NY, USA). Normality of continuous variables was assessed with the Shapiro-Wilk test. Differences in quadrant-level visibility were evaluated using the McNemar test for paired binary outcomes. Differences in axial length and spherical equivalent between Clarus-further and Optos-further eyes were compared with the Mann Whitney U test. Logistic regression was used to examine predictive relationships. Receiver operating characteristic analysis was performed to assess the ability of axial length to predict cases in which Clarus reached farther into the periphery, and the optimal cutoff was identified using the Youden index. A p value < 0.05 was considered statistically significant. Figures were prepared using GraphPad Prism Version 10.2.0 (GraphPad Software, San Diego, CA, USA), Microsoft Excel and Microsoft PowerPoint (Microsoft Corporation, Redmond, WA, USA) and Matplotlib Version 3.8. Results Study population Twenty-six eyes of 26 participants were included in the final analysis. The study cohort consisted of 14 female and 12 male individuals, reflecting a well-balanced sample of adults undergoing UWF retinal imaging. Baseline demographic and biometric characteristics are summarized in Table 1 . The participants exhibited a broad spectrum of refractive states, ranging from moderate hyperopia to high myopia, and axial length values demonstrated substantial anatomical variability (20.99–26.84 mm). This diversity provided an ideal setting for exploring the influence of ocular geometry on peripheral visualization. Table 1 Study population and peripheral imaging results Variable Total (n = 26) Clarus further (n = 15) Optos further (n = 11) Statistical Test p-value Sex (F/M) 14 / 12 - - - - Laterality (Right/Left) 13 / 13 - - - - Lens status Phakic: 24 / Pseudophakic: 2 - - - - LOCS III cataract grading NO1–NO3, C1–C3, PSC1–PSC3; mixed codes present - - - - Age (years) 75.3 ± 8.9 73.4 ± 8.7 77.9 ± 8.5 Mann-Whitney U 0.194 Spherical power (D) −0.34 ± 4.30 (-8–7.75) -1.38 ± 4.8 + 1.12 ± 3.6 Mann-Whitney U 0.149 Cylinder (D) 0.59 ± 0.49 0.54 ± 0.45 0.65 ± 0.51 Mann-Whitney U 0.590 Spherical equivalent (D) −0.04 ± 4.29 (-5.75–7.88) -2.05 ± 4.52 + 2.69 ± 2.56 Mann-Whitney U 0.019 Axial length (mm) 23.36 ± 1.53 (20.99–26.84) 23.97 ± 1.62 22.53 ± 0.94 Mann-Whitney U 0.016 ST visibility (Clarus vs Optos) - 50% 50% McNemar 1.000 SN visibility (Clarus vs Optos) - 57.7% 42.3% McNemar 0.557 IT visibility (Clarus vs Optos) - 50% 50% McNemar 1.000 IN visibility (Clarus vs Optos) - 50% 50% McNemar 1.000 Logistic regression (Axial length) OR = 2.39 (95% CI 1.07–5.32) - - Logistic Regression 0.033 ROC AUC (Axial length) AUC = 0.782 Cutoff = 23.77 mm - ROC - All eyes had sufficiently clear ocular media, confirmed by standardized LOCS III grading, to allow high quality UWF imaging. Participants maintained stable fixation, and image acquisition was successfully completed with both the Clarus 500 and the Optos Daytona in all evaluated eyes. Four images were excluded due to failed montage generation or insufficient image quality, while all remaining images met the criteria for clinical interpretability, ensuring a complete and reliable dataset for subsequent quadrant-level comparisons and biometric analyses. Quadrant-level comparison of peripheral visibility Across all four examined quadrants, the Clarus 500 and the Optos Daytona demonstrated highly comparable performance in reaching the farthest clinically interpretable retinal point. As illustrated in Fig. 1 , the proportion of quadrants in which each device achieved the most peripheral identifiable structure showed no meaningful divergence. Statistical confirmation using the McNemar test revealed perfect equivalence in the superior temporal, inferior temporal and inferior nasal quadrants, with each comparison yielding p = 1.000. In the superior nasal quadrant, a tendency favoring the Clarus system was observed; however, this difference did not reach statistical significance (p = 0.557). Taken together, these findings indicate that under routine clinical imaging conditions, both devices provide essentially identical functional reach into the far periphery. Figure 2 offers representative examples of the peripheral endpoints assessed in this analysis. The images underscore the more anatomically preserved true-color depiction produced by the Clarus 500, contrasted with the characteristic geometric stretching of the extreme periphery often seen in scanning-laser ophthalmoscopy images from the Optos Daytona. These examples help clarify that the evaluation focused strictly on the farthest clinically interpretable retinal structure rather than on the geometric boundary of the captured image. Influence of ocular biometry A more differentiated pattern emerged when biometric characteristics were incorporated into the analysis. Eyes in which the Clarus system reached farther into the superior nasal quadrant exhibited significantly greater axial lengths than those in which the Optos demonstrated superior reach (23.97 ± 1.62 mm vs. 22.53 ± 0.94 mm; p = 0.016), as shown in Fig. 3 A. This observation reflects the biomechanical influence of ocular elongation on peripheral visibility. A parallel association was observed in refractive error. Eyes classified as Clarus-further tended to be more myopic, whereas Optos-further eyes displayed more hyperopic refractive states. This difference in spherical equivalent reached statistical significance (− 2.05 ± 4.52 D vs. +2.69 ± 2.56 D; p = 0.019), as demonstrated in Fig. 3 B. These findings indicate that myopic ocular geometry, characterized by axial elongation and altered peripheral curvature, may selectively enhance Clarus visualization in the superior nasal field. No significant associations were detected between device performance and age or cylindrical power. Thus, the biometric factors most relevant for determining quadrant-specific device advantages appear to be axial length and spherical equivalent. Predictive value of axial length To further explore the relationship between ocular geometry and device performance, logistic regression analysis was conducted. In univariate analysis, axial length emerged as a significant predictor of Clarus superiority in the superior nasal quadrant (OR 2.39, 95% CI 1.07–5.32; p = 0.033). Although axial length did not retain significance in the multivariate model after adjustment for age and spherical equivalent, the full model remained statistically significant (p = 0.011), indicating that biometric parameters influence device performance collectively rather than independently. Receiver operating characteristic analysis supported the predictive relevance of axial length. As illustrated in Fig. 4 , axial length showed good discriminatory power in determining whether Clarus would reach farther into the superior nasal periphery (AUC = 0.782). The optimal cutoff, derived using the Youden index, was 23.77 mm, corresponding to a sensitivity of 0.60 and a specificity of 0.91. Discussion In this comparative widefield imaging study, the Clarus 500 and the Optos Daytona demonstrated an overall similar ability to visualize the farthest clinically assessable peripheral point across all four retinal quadrants. Despite the fundamental optical differences between the two systems, their quadrant-level performance was largely equivalent. No statistically significant differences were observed in the superior temporal, inferior temporal or inferior nasal quadrants, and even in the superior nasal quadrant, where a mild descriptive imbalance was noted, the trend did not reach statistical significance. These findings are consistent with previous comparative analyses, which have shown that although each device has characteristic strengths, neither system exhibits a universal advantage across all anatomical regions [ 4 , 6 , 7 , 10 , 11 ]. A more differentiated picture emerged when ocular biometry was considered. Eyes in which the Clarus reached farther into the superior nasal periphery exhibited significantly longer axial lengths and more myopic refractive profiles than those in which the Optos achieved greater peripheral visibility. This relationship was supported not only by descriptive comparisons but also by statistical testing, including logistic regression and receiver operating characteristic analysis. Axial length demonstrated a meaningful discriminatory capacity, with an optimal threshold near 23.77 mm, indicating that the biomechanical and geometric properties of long, myopic eyes confer a measurable visualization advantage to the Clarus system in this quadrant [ 14 – 16 ]. These biometric findings align well with the known optical characteristics of both devices. The Clarus 500 uses partially confocal true-color imaging with broad-spectrum RGB illumination, resulting in more anatomically faithful representations and reduced peripheral distortion. The more regular retinal curvature and altered peripheral reflectance patterns of highly myopic eyes appear to synergize with the Clarus optical design, enabling more stable preservation of structural detail in the superior nasal field [ 4 , 6 , 10 ]. In contrast, the Optos Daytona employs a dual-wavelength scanning laser system paired with an ellipsoidal mirror to generate a nominal 200-degree field of view. While this enables an exceptionally broad single-capture image, the associated projection geometry introduces nonuniform magnification and peripheral stretching, particularly in the superior and nasal regions [ 5 ]. These distortions tend to become more pronounced in eyes with greater axial elongation, which may limit the interpretability of fine peripheral structures. Representative image excerpts in Fig. 2 visually demonstrate these differences in peripheral geometry and interpretation. Interestingly, although hyperopic or shorter eyes descriptively tended to fall into the Optos-further group, this pattern was not statistically supported. Neither the Mann-Whitney U comparisons nor logistic regression identified short axial length or hyperopic refractive state as reliable predictors of Optos advantage. This distinction is important because it clarifies that the observed Clarus benefit in long eyes does not mirror a corresponding Optos benefit in shorter eyes. Earlier literature suggested the possibility of such a relationship [ 14 , 15 ], but the present findings refine this view by showing that only the influence of axial elongation on Clarus performance is statistically robust, whereas no analogous effect was confirmed for the Optos system. A key strength of this study lies in its use of a clinically meaningful outcome measure. Rather than relying on nominal field-of-view specifications or geometric image boundaries, we evaluated the farthest clinically interpretable retinal structure. As illustrated in Fig. 2 , geometric image edges may contain minimal or no diagnostic information, especially in regions affected by optical stretching or reduced illumination. By focusing on the last identifiable vessel branch, pigmentary alteration or peripheral lesion, the analysis more accurately reflects the real-world diagnostic utility of each system [ 4 , 6 , 10 ]. Several limitations must be acknowledged. The sample size was modest but aligned with paired widefield imaging comparisons. Imaging was performed under non-dilated conditions, a design choice intended to simulate real-world workflow, although it may have limited peripheral visibility in eyes with small pupils or early lens opacities [ 7 ]. Additionally, the quadrant-based assessment offers a clear and reproducible comparison framework but does not capture granular variation within quadrants. Future work using finer topographic mapping or automated methods may provide deeper characterization. Despite these limitations, the consistent association between axial elongation and superior Clarus performance in the superior nasal quadrant strengthens the reliability of this finding. Taken together, the results provide new insight into the interaction between ocular biometry and widefield imaging performance. While the Clarus 500 and Optos Daytona perform comparably across most quadrants, axial elongation and myopic ocular geometry selectively enhance Clarus performance in the superior nasal periphery, a region frequently involved in lattice degeneration and peripheral retinal tears and in which approximately 40% of rhegmatogenous retinal detachments demonstrate a break within the superior nasal quadrant [ 18 ]. These observations underscore the importance of considering ocular shape in device-specific interpretation and suggest that biometric variables warrant greater attention in future widefield imaging research. Importantly, beyond these nuanced biometric effects, the findings reaffirm that both the Clarus 500 and the Optos Daytona deliver robust, high-quality UWF imaging performance in routine clinical settings. Both devices reliably visualize clinically meaningful peripheral structures and can be considered effective tools for comprehensive peripheral retinal assessment, although visualization of the extreme far periphery remains inherently limited in both systems due to optical and anatomical constraints. Conclusion Overall, the findings of this study indicate that both the Clarus 500 and the Optos Daytona provide robust and reliable widefield retinal imaging with largely comparable peripheral visualization across most quadrants. The only statistically meaningful distinction arose in the superior nasal quadrant, where longer axial length and more myopic refractive profiles favored Clarus performance, with an axial-length threshold near 23.77 mm marking the point at which this advantage became evident. Although shorter, more hyperopic eyes showed a descriptive tendency toward greater peripheral reach with the Optos Daytona, this trend did not achieve statistical significance and therefore should not be interpreted as a true performance benefit. Taken together, these results underscore that device behavior in the far periphery is shaped not only by optical design but also by ocular geometry, and they highlight the value of considering axial length when interpreting or selecting widefield imaging systems. Importantly, despite these nuanced biometric effects, both devices performed strongly and consistently overall, supporting their use as dependable tools for comprehensive peripheral retinal assessment. Abbreviations AUC Area under the curve BCVA Best corrected visual acuity IOL Intraocular lens IRMA Intraretinal microvascular abnormalities LOCS III Lens Opacities Classification System III NPDR Non–proliferative diabetic retinopathy RGB Red, green, blue ROC Receiver operating characteristic SD Standard deviation SE Spherical equivalent UWF Ultra–widefield Declarations Ethics approval and consent to participate This study was approved by the Ethics Committee of the City of Vienna (approval number EK19-207-0919), registered at clinicaltrials.gov (NCT04255732), and conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all participants prior to inclusion. Consent for publication Not applicable. Availability of data and materials The datasets generated and analyzed during this study are available from the corresponding author upon reasonable request. Competing interests OF serves as a scientific advisor to Carl Zeiss Meditec AG, Croma, and Johnson & Johnson. All other authors declare no conflicts of interest. Funding This study was not supported by any sponsor or funder. Author Contributions CS, AF, MR: Study conception and design, image acquisition (MR), data analysis, manuscript drafting. CS: Image evaluation, statistical analysis, data interpretation, manuscript revision. MR, AF: Biometry acquisition, data curation, methodology support. OF: Supervision, critical review of the manuscript, interpretation of results. CS, AF, MR, OF: Final approval of the version to be published. Acknowledgements Not applicable. References Byer NE. Lattice degeneration of the retina. Surv Ophthalmol. 1979;23(4):213–48. Wilkinson CP. Evidence-based analysis of prophylactic treatment of asymptomatic retinal breaks and lattice degeneration. Ophthalmology. 2000;107(1):12–5. discussion 15–18. Kuhn F, Aylward B. 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Comparative Evaluation of Field of View Across Widefield Retinal Imaging Systems. Transl Vis Sci Technol. 2025;14(11):20. Khan M, Kovacs K, Guan I, Goldblatt N, Foulsham W, Wu A, Papakostas T, Gupta M, D'Amico DJ, Kiss S, et al. Evaluating Ultra-Widefield Imaging Utility in the Detection of Treatment-Requiring Peripheral Retinal Tears and Holes. Retina. 2024;44(1):71–7. Jonas JB, Panda-Jonas S, Pan Z, Xu J, Wang YX. Posterior Eye Shape in Myopia. Ophthalmol Sci. 2024;4(6):100575. Verkicharla PK, Mathur A, Mallen EA, Pope JM, Atchison DA. Eye shape and retinal shape, and their relation to peripheral refraction. Ophthalmic Physiol Opt. 2012;32(3):184–99. Xu F, Hu X, Wang Y, Wei R, Yu Y, Peng Y, Li M, Wu H. The Specificity Rates of Clarus 500 Ultra-Wide-Field Retinal Imaging for Detecting Peripheral Retinal Lesions in Medium-to-High Myopia Eyes. Ophthalmic Res. 2025;68(1):352–9. Chylack LT Jr., Wolfe JK, Singer DM, Leske MC, Bullimore MA, Bailey IL, Friend J, McCarthy D, Wu SY. The Lens Opacities Classification System III. The Longitudinal Study of Cataract Study Group. Arch Ophthalmol. 1993;111(6):831–6. Shunmugam M, Shah AN, Hysi PG, Williamson TH. The pattern and distribution of retinal breaks in eyes with rhegmatogenous retinal detachment. Am J Ophthalmol. 2014;157(1):221–e226221. Additional Declarations Competing interest reported. OF serves as a scientific advisor to Carl Zeiss Meditec AG, Croma, and Johnson & Johnson. All other authors declare no conflicts of interest. Cite Share Download PDF Status: Published Journal Publication published 11 Apr, 2026 Read the published version in BMC Ophthalmology → Version 1 posted Editorial decision: Revision requested 30 Jan, 2026 Reviews received at journal 25 Jan, 2026 Reviews received at journal 09 Jan, 2026 Reviews received at journal 09 Jan, 2026 Reviewers agreed at journal 07 Jan, 2026 Reviewers agreed at journal 07 Jan, 2026 Reviewers agreed at journal 07 Jan, 2026 Reviewers invited by journal 07 Jan, 2026 Editor invited by journal 17 Dec, 2025 Editor assigned by journal 16 Dec, 2025 Submission checks completed at journal 16 Dec, 2025 First submitted to journal 15 Dec, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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17:53:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8369016/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8369016/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1186/s12886-026-04782-0","type":"published","date":"2026-04-11T15:58:52+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":100361963,"identity":"3efc0489-f259-4bbe-9737-e039f027a2e8","added_by":"auto","created_at":"2026-01-16 07:45:59","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":3196439,"visible":true,"origin":"","legend":"","description":"","filename":"ManuskriptClarusvsOptos20251215.docx","url":"https://assets-eu.researchsquare.com/files/rs-8369016/v1/822ddfcf702988610d94b650.docx"},{"id":100009490,"identity":"1d2248f0-e225-43c4-935a-301e9b3e28c3","added_by":"auto","created_at":"2026-01-12 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06:02:41","extension":"xml","order_by":11,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":78817,"visible":true,"origin":"","legend":"","description":"","filename":"9ed20d7a30fd450f873376fc9e8e79771structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8369016/v1/0047070a10d6416fe6dad555.xml"},{"id":100009502,"identity":"e65be36a-3fe5-481e-be33-149800d15803","added_by":"auto","created_at":"2026-01-12 06:02:41","extension":"html","order_by":12,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":87693,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8369016/v1/7a10192c02074b533ddfb967.html"},{"id":100361871,"identity":"3d18363b-cfe6-41aa-b54d-7725989092f1","added_by":"auto","created_at":"2026-01-16 07:45:52","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":44441,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eProportion of eyes in which Clarus 500 or Optos Daytona reached the farthest clinically assessable peripheral point in each quadrant.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis figure shows, for each of the four retinal quadrants, the proportion of eyes in which Clarus or Optos allowed visualization of the most peripheral anatomically interpretable retinal structure. The two systems performed similarly across all quadrants, with no statistically significant differences detected.\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8369016/v1/8a3a767b5a6eec12372e105c.png"},{"id":100361691,"identity":"287d3e89-73dc-4413-a632-6d79fcc6053b","added_by":"auto","created_at":"2026-01-16 07:45:30","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":2803172,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eRepresentative full-field (upper) and peripheral supero-nasal (lower)images of the Clarus 500 (left) and Optos Daytona (right).\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8369016/v1/343719bf5bc0e68ba0479bb1.png"},{"id":100009498,"identity":"3feb99f2-6447-4c73-9665-ca63da65a91e","added_by":"auto","created_at":"2026-01-12 06:02:40","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":227149,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDistribution of axial length (left) and refraction (right) of eyes in which Clarus or Optos reached farther in the superior nasal quadrant.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8369016/v1/69662bdf788920191132d8e0.jpeg"},{"id":100009491,"identity":"715abbcc-c1a6-40e9-9cd4-fad2a813a45e","added_by":"auto","created_at":"2026-01-12 06:02:40","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":45487,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eReceiver operating characteristic curve for axial length predicting Clarus superiority in the superior nasal quadrant.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe area under the curve was 0.782, indicating good discriminatory performance, and the optimal threshold for axial length was 23.77 mm.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8369016/v1/fbf3f33633d297261a297ada.png"},{"id":106809443,"identity":"7f221e81-d506-4717-a6e7-5d198e6c4a24","added_by":"auto","created_at":"2026-04-13 16:10:56","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":5516859,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8369016/v1/ba5ee683-0f88-4b89-80f1-064ba55c876f.pdf"}],"financialInterests":"Competing interest reported. OF serves as a scientific advisor to Carl Zeiss Meditec AG, Croma, and Johnson \u0026 Johnson. All other authors declare no conflicts of interest.","formattedTitle":"Influence of ocular biometry on peripheral retinal visualization: A comparative study of Clarus and Optos widefield imaging systems","fulltext":[{"header":"Introduction","content":"\u003cp\u003eUltra-widefield (UWF) retinal imaging has transformed modern ophthalmic diagnostics by enabling clinicians to examine the peripheral retina far beyond the coverage of conventional fundus photography. Standard cameras typically visualize only a limited portion of the posterior pole, which leaves large areas of the mid-periphery and far periphery unassessed. This becomes clinically relevant because numerous retinal abnormalities arise preferentially in these regions. Conditions such as lattice degeneration, white without pressure, cobblestone degeneration, peripheral pigment alterations and asymptomatic retinal breaks may influence the risk of rhegmatogenous retinal detachment or guide management strategies in patients with peripheral retinal disease [\u003cspan additionalcitationids=\"CR2\" citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Consequently, the ability to reliably determine the most distant clinically interpretable peripheral point in each quadrant is essential for accurate screening, risk stratification and longitudinal patient care. This is particularly relevant in settings where subtle peripheral pathology may precede sight-threatening events, such as the use of widefield imaging to screen for early retinal detachment in eyes undergoing intravitreal injection.\u003c/p\u003e \u003cp\u003eUWF imaging systems were developed to address the limitations of conventional photography by expanding the field of view and offering a more comprehensive visualization of retinal anatomy. Among these systems, the Zeiss Clarus 500 and the Optos Daytona have gained particular prominence in routine clinical practice. Although both are considered widefield imaging platforms, they are based on fundamentally different optical concepts.\u003c/p\u003e \u003cp\u003eThe Clarus 500 uses a design that relies on partially confocal imaging and broad-spectrum RGB illumination to produce true-color images with reduced peripheral distortion [\u003cspan additionalcitationids=\"CR5\" citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. A single image provides a field of approximately 133 degrees, and two sequential captures can be combined into a montage that reaches a field comparable to that of the Optos system. This approach results in more anatomically realistic contours, improved color representation and fewer eyelash artifacts. At the same time, the use of a montage and the need for stable fixation may introduce practical limitations when attempting to visualize the most extreme periphery [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAlternative, the Optos Daytona acquires a nominal 200-degree retinal field through a single dual-wavelength scanning laser exposure supported by an ellipsoidal mirror configuration that allows imaging without pharmacologic dilation [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. This enables rapid acquisition and extensive field coverage. However, the geometry inherent to the scanning and projection process creates nonuniform peripheral magnification and peripheral stretching, especially toward the far temporal and nasal regions, which may modify the appearance of the extreme periphery and influence the visibility of subtle anatomical details [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eComparative investigations across various UWF platforms have shown that differences in illumination, optical geometry, confocality and image processing directly affect peripheral visibility. Studies in diabetic retinopathy have demonstrated that both the Clarus and Optos systems offer reliable lesion detection but differ in the balance between field extent, color rendering and susceptibility to artifacts [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Additional research comparing field size and the distribution of clinically relevant features has emphasized that the nominal field of view alone does not adequately describe the functional extent of the clinically interpretable image. Instead, factors such as local retinal curvature, edge distortion patterns and illumination uniformity play a major role in determining how far into the periphery meaningful diagnostic information can be obtained [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDespite the widespread use of these technologies, limited work has focused on the precise quantification of the farthest clinically interpretable peripheral point in each quadrant. Many earlier studies assessed overall field size, global image quality or the presence of specific peripheral lesions, but they did not evaluate the actual anatomical limit up to which structures remain interpretable. This limitation is clinically relevant because UWF imaging demonstrates only moderate sensitivity but high specificity for detecting treatment-requiring retinal tears and holes, even when interrater agreement is high [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Consequently, the clinically assessable retinal boundary cannot be inferred from nominal field specifications alone; it reflects the combined influence of optical design, projection geometry, patient-specific anatomical factors and the interaction between the imaging beam and the peripheral globe contour.\u003c/p\u003e \u003cp\u003eAn additional factor that may affect peripheral visualization is ocular biometry, particularly axial length and refractive state. Eyes with long axial length typically display differences in retinal curvature, posterior contour and peripheral shape compared with eyes of shorter axial length. These anatomical variations can influence the interaction between UWF imaging beams and the retinal surface and may alter the effective peripheral visibility achieved by different imaging systems [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Although Clarus performance has been investigated in cohorts with medium to high myopia [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], the combined evaluation of biometric influences in direct comparisons between Clarus and Optos remains limited in the existing literature and therefore represents a meaningful area of investigation.\u003c/p\u003e \u003cp\u003eThe aim of the present study is to compare the Clarus 500 and Optos Daytona with respect to their ability to visualize the farthest clinically assessable peripheral point in the four standard retinal quadrants. The study further examines the relationship between peripheral visibility and ocular biometry, including axial length and spherical equivalent. By focusing on the clinically interpretable boundary rather than nominal field specifications, this investigation provides a functional assessment of peripheral visualization and contributes to a more comprehensive understanding of how device design and ocular anatomy interact in UWF retinal imaging.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e This prospective paired comparative imaging study was approved by the institutional ethics committee (EK19-207-0919), registered at clinicaltrials.gov (NCT04255732) and conducted in accordance with the declaration of Helsinki. Twenty-six eyes from 30 adult participants were enrolled. Written informed consent was obtained from all subjects before participation. All individuals underwent same-day non-dilated UWF imaging with both the Clarus 500 (Carl Zeiss Meditec, Jena, Germany) and the Optos Daytona (Optos plc, Dunfermline, UK). To minimize potential order effects related to accommodation, fixation stability or tear-film variability, the sequence of device imaging was randomized for each participant using an online randomization tool (Randomizer, \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ewww.randomizer.org\u003c/span\u003e\u003cspan address=\"http://www.randomizer.org\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eEligibility required clear ocular media suitable for widefield imaging, stable fixation and the successful acquisition of clinically interpretable images on both devices. To ensure that lens opacities did not impair the ability to evaluate the far periphery, all participants underwent a standardized cataract assessment using the Lens Opacities Classification System III (LOCS III) [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Eyes with dense cataracts were excluded. Further exclusion criteria included any history of retinal detachment, previous vitreoretinal surgery, dense media opacities, poor fixation or insufficient image quality due to blinking or motion artifacts.\u003c/p\u003e \u003cp\u003eAxial length was measured using the IOLMaster 700 (Carl Zeiss Meditec AG, Jena, Germany), a swept-source optical biometer equipped with multidot keratometry. Refractive data were assessed with subjective refraction and noted as sphere and cylinder, and the spherical equivalent was calculated as sphere plus half of the cylindrical power.\u003c/p\u003e \u003cp\u003eThe Clarus 500 (Carl Zeiss Meditec AG, Jena, Germany) uses partially confocal true-color imaging with broad-spectrum RGB illumination and produces anatomically faithful images with reduced peripheral distortion. A single acquisition covers approximately 133 degrees and can be extended through a two-image montage.\u003c/p\u003e \u003cp\u003eThe Optos Daytona (Optos plc, Dunfermline, UK) employs dual-wavelength scanning laser illumination at 532 nanometers and 633 nanometers combined with an ellipsoidal mirror, allowing a nominal field of approximately 200 degrees in a single nonmydriatic capture. Peripheral regions of the Daytona images frequently show characteristic stretching and nonuniform magnification. All imaging was performed by the same experienced operator, and the sequence of device acquisition was randomized to reduce the influence of accommodation, tear-film variability and fixation fatigue.\u003c/p\u003e \u003cp\u003eThe primary study outcome was the farthest clinically assessable peripheral point in each of the four quadrants. This point was defined as the most peripheral retinal structure that remained clearly visible and diagnostically interpretable. Acceptable structures included peripheral vascular branches, pigmentary alterations and lattice degeneration. Peripheral areas in which the image boundary was visible, but no structure could be confidently recognized were not considered clinically assessable. One masked retina specialist independently reviewed all images and was unaware of the imaging sequence and biometric measurements. All peripheral structures and measurement endpoints were evaluated using ImageJ (Version 2.0.0 rc43/125n) ensuring standardized and reproducible image assessment.\u003c/p\u003e \u003cp\u003eFor each quadrant, visibility was categorized as Clarus further, Optos further, or equal. Associations between device performance and biometric parameters including axial length, spherical equivalent and age were examined. Statistical analyses were conducted using IBM SPSS Statistics Version 29.0.0.0 (IBM Corp., Armonk, NY, USA).\u003c/p\u003e \u003cp\u003eNormality of continuous variables was assessed with the Shapiro-Wilk test. Differences in quadrant-level visibility were evaluated using the McNemar test for paired binary outcomes. Differences in axial length and spherical equivalent between Clarus-further and Optos-further eyes were compared with the Mann Whitney U test. Logistic regression was used to examine predictive relationships. Receiver operating characteristic analysis was performed to assess the ability of axial length to predict cases in which Clarus reached farther into the periphery, and the optimal cutoff was identified using the Youden index. A p value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e \u003cp\u003eFigures were prepared using GraphPad Prism Version 10.2.0 (GraphPad Software, San Diego, CA, USA), Microsoft Excel and Microsoft PowerPoint (Microsoft Corporation, Redmond, WA, USA) and Matplotlib Version 3.8.\u003c/p\u003e"},{"header":"Results","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eStudy population\u003c/h2\u003e \u003cp\u003eTwenty-six eyes of 26 participants were included in the final analysis. The study cohort consisted of 14 female and 12 male individuals, reflecting a well-balanced sample of adults undergoing UWF retinal imaging. Baseline demographic and biometric characteristics are summarized in Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The participants exhibited a broad spectrum of refractive states, ranging from moderate hyperopia to high myopia, and axial length values demonstrated substantial anatomical variability (20.99\u0026ndash;26.84 mm). This diversity provided an ideal setting for exploring the influence of ocular geometry on peripheral visualization.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eStudy population and peripheral imaging results\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eVariable\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eTotal (n\u0026thinsp;=\u0026thinsp;26)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eClarus further (n\u0026thinsp;=\u0026thinsp;15)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eOptos further (n\u0026thinsp;=\u0026thinsp;11)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eStatistical Test\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ep-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSex (F/M)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14 / 12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLaterality (Right/Left)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e13 / 13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLens status\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePhakic: 24 / Pseudophakic: 2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLOCS III cataract grading\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eNO1\u0026ndash;NO3, C1\u0026ndash;C3, PSC1\u0026ndash;PSC3; mixed codes present\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAge (years)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e75.3\u0026thinsp;\u0026plusmn;\u0026thinsp;8.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e73.4\u0026thinsp;\u0026plusmn;\u0026thinsp;8.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e77.9\u0026thinsp;\u0026plusmn;\u0026thinsp;8.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMann-Whitney U\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.194\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSpherical power (D)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus;0.34\u0026thinsp;\u0026plusmn;\u0026thinsp;4.30\u003c/p\u003e \u003cp\u003e(-8\u0026ndash;7.75)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-1.38\u0026thinsp;\u0026plusmn;\u0026thinsp;4.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e+\u0026thinsp;1.12\u0026thinsp;\u0026plusmn;\u0026thinsp;3.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMann-Whitney U\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.149\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eCylinder (D)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.59\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.65\u0026thinsp;\u0026plusmn;\u0026thinsp;0.51\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMann-Whitney U\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.590\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSpherical equivalent (D)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026minus;0.04\u0026thinsp;\u0026plusmn;\u0026thinsp;4.29\u003c/p\u003e \u003cp\u003e(-5.75\u0026ndash;7.88)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-2.05\u0026thinsp;\u0026plusmn;\u0026thinsp;4.52\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e+\u0026thinsp;2.69\u0026thinsp;\u0026plusmn;\u0026thinsp;2.56\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMann-Whitney U\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.019\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eAxial length (mm)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23.36\u0026thinsp;\u0026plusmn;\u0026thinsp;1.53\u003c/p\u003e \u003cp\u003e(20.99\u0026ndash;26.84)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23.97\u0026thinsp;\u0026plusmn;\u0026thinsp;1.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e22.53\u0026thinsp;\u0026plusmn;\u0026thinsp;0.94\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMann-Whitney U\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.016\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eST visibility (Clarus vs Optos)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e50%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMcNemar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eSN visibility (Clarus vs Optos)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e57.7%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e42.3%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMcNemar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.557\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eIT visibility (Clarus vs Optos)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e50%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMcNemar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eIN visibility (Clarus vs Optos)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e50%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eMcNemar\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.000\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eLogistic regression (Axial length)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eOR\u0026thinsp;=\u0026thinsp;2.39 (95% CI 1.07\u0026ndash;5.32)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eLogistic Regression\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.033\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003eROC AUC (Axial length)\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eAUC\u0026thinsp;=\u0026thinsp;0.782\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eCutoff\u0026thinsp;=\u0026thinsp;23.77 mm\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eROC\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e-\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAll eyes had sufficiently clear ocular media, confirmed by standardized LOCS III grading, to allow high quality UWF imaging. Participants maintained stable fixation, and image acquisition was successfully completed with both the Clarus 500 and the Optos Daytona in all evaluated eyes. Four images were excluded due to failed montage generation or insufficient image quality, while all remaining images met the criteria for clinical interpretability, ensuring a complete and reliable dataset for subsequent quadrant-level comparisons and biometric analyses.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eQuadrant-level comparison of peripheral visibility\u003c/h3\u003e\n\u003cp\u003eAcross all four examined quadrants, the Clarus 500 and the Optos Daytona demonstrated highly comparable performance in reaching the farthest clinically interpretable retinal point. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, the proportion of quadrants in which each device achieved the most peripheral identifiable structure showed no meaningful divergence.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eStatistical confirmation using the McNemar test revealed perfect equivalence in the superior temporal, inferior temporal and inferior nasal quadrants, with each comparison yielding p\u0026thinsp;=\u0026thinsp;1.000. In the superior nasal quadrant, a tendency favoring the Clarus system was observed; however, this difference did not reach statistical significance (p\u0026thinsp;=\u0026thinsp;0.557). Taken together, these findings indicate that under routine clinical imaging conditions, both devices provide essentially identical functional reach into the far periphery.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e offers representative examples of the peripheral endpoints assessed in this analysis. The images underscore the more anatomically preserved true-color depiction produced by the Clarus 500, contrasted with the characteristic geometric stretching of the extreme periphery often seen in scanning-laser ophthalmoscopy images from the Optos Daytona. These examples help clarify that the evaluation focused strictly on the farthest clinically interpretable retinal structure rather than on the geometric boundary of the captured image.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eInfluence of ocular biometry\u003c/h3\u003e\n\u003cp\u003eA more differentiated pattern emerged when biometric characteristics were incorporated into the analysis. Eyes in which the Clarus system reached farther into the superior nasal quadrant exhibited significantly greater axial lengths than those in which the Optos demonstrated superior reach (23.97\u0026thinsp;\u0026plusmn;\u0026thinsp;1.62 mm vs. 22.53\u0026thinsp;\u0026plusmn;\u0026thinsp;0.94 mm; p\u0026thinsp;=\u0026thinsp;0.016), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA. This observation reflects the biomechanical influence of ocular elongation on peripheral visibility.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA parallel association was observed in refractive error. Eyes classified as Clarus-further tended to be more myopic, whereas Optos-further eyes displayed more hyperopic refractive states. This difference in spherical equivalent reached statistical significance (\u0026minus;\u0026thinsp;2.05\u0026thinsp;\u0026plusmn;\u0026thinsp;4.52 D vs. +2.69\u0026thinsp;\u0026plusmn;\u0026thinsp;2.56 D; p\u0026thinsp;=\u0026thinsp;0.019), as demonstrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB. These findings indicate that myopic ocular geometry, characterized by axial elongation and altered peripheral curvature, may selectively enhance Clarus visualization in the superior nasal field.\u003c/p\u003e \u003cp\u003eNo significant associations were detected between device performance and age or cylindrical power. Thus, the biometric factors most relevant for determining quadrant-specific device advantages appear to be axial length and spherical equivalent.\u003c/p\u003e\n\u003ch3\u003ePredictive value of axial length\u003c/h3\u003e\n\u003cp\u003eTo further explore the relationship between ocular geometry and device performance, logistic regression analysis was conducted. In univariate analysis, axial length emerged as a significant predictor of Clarus superiority in the superior nasal quadrant (OR 2.39, 95% CI 1.07\u0026ndash;5.32; p\u0026thinsp;=\u0026thinsp;0.033). Although axial length did not retain significance in the multivariate model after adjustment for age and spherical equivalent, the full model remained statistically significant (p\u0026thinsp;=\u0026thinsp;0.011), indicating that biometric parameters influence device performance collectively rather than independently.\u003c/p\u003e \u003cp\u003eReceiver operating characteristic analysis supported the predictive relevance of axial length. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, axial length showed good discriminatory power in determining whether Clarus would reach farther into the superior nasal periphery (AUC\u0026thinsp;=\u0026thinsp;0.782). The optimal cutoff, derived using the Youden index, was 23.77 mm, corresponding to a sensitivity of 0.60 and a specificity of 0.91.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eIn this comparative widefield imaging study, the Clarus 500 and the Optos Daytona demonstrated an overall similar ability to visualize the farthest clinically assessable peripheral point across all four retinal quadrants. Despite the fundamental optical differences between the two systems, their quadrant-level performance was largely equivalent. No statistically significant differences were observed in the superior temporal, inferior temporal or inferior nasal quadrants, and even in the superior nasal quadrant, where a mild descriptive imbalance was noted, the trend did not reach statistical significance. These findings are consistent with previous comparative analyses, which have shown that although each device has characteristic strengths, neither system exhibits a universal advantage across all anatomical regions [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eA more differentiated picture emerged when ocular biometry was considered. Eyes in which the Clarus reached farther into the superior nasal periphery exhibited significantly longer axial lengths and more myopic refractive profiles than those in which the Optos achieved greater peripheral visibility. This relationship was supported not only by descriptive comparisons but also by statistical testing, including logistic regression and receiver operating characteristic analysis. Axial length demonstrated a meaningful discriminatory capacity, with an optimal threshold near 23.77 mm, indicating that the biomechanical and geometric properties of long, myopic eyes confer a measurable visualization advantage to the Clarus system in this quadrant [\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThese biometric findings align well with the known optical characteristics of both devices. The Clarus 500 uses partially confocal true-color imaging with broad-spectrum RGB illumination, resulting in more anatomically faithful representations and reduced peripheral distortion. The more regular retinal curvature and altered peripheral reflectance patterns of highly myopic eyes appear to synergize with the Clarus optical design, enabling more stable preservation of structural detail in the superior nasal field [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. In contrast, the Optos Daytona employs a dual-wavelength scanning laser system paired with an ellipsoidal mirror to generate a nominal 200-degree field of view. While this enables an exceptionally broad single-capture image, the associated projection geometry introduces nonuniform magnification and peripheral stretching, particularly in the superior and nasal regions [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. These distortions tend to become more pronounced in eyes with greater axial elongation, which may limit the interpretability of fine peripheral structures. Representative image excerpts in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e visually demonstrate these differences in peripheral geometry and interpretation.\u003c/p\u003e \u003cp\u003eInterestingly, although hyperopic or shorter eyes descriptively tended to fall into the Optos-further group, this pattern was not statistically supported. Neither the Mann-Whitney U comparisons nor logistic regression identified short axial length or hyperopic refractive state as reliable predictors of Optos advantage. This distinction is important because it clarifies that the observed Clarus benefit in long eyes does not mirror a corresponding Optos benefit in shorter eyes. Earlier literature suggested the possibility of such a relationship [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e], but the present findings refine this view by showing that only the influence of axial elongation on Clarus performance is statistically robust, whereas no analogous effect was confirmed for the Optos system.\u003c/p\u003e \u003cp\u003eA key strength of this study lies in its use of a clinically meaningful outcome measure. Rather than relying on nominal field-of-view specifications or geometric image boundaries, we evaluated the farthest clinically interpretable retinal structure. As illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, geometric image edges may contain minimal or no diagnostic information, especially in regions affected by optical stretching or reduced illumination. By focusing on the last identifiable vessel branch, pigmentary alteration or peripheral lesion, the analysis more accurately reflects the real-world diagnostic utility of each system [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSeveral limitations must be acknowledged. The sample size was modest but aligned with paired widefield imaging comparisons. Imaging was performed under non-dilated conditions, a design choice intended to simulate real-world workflow, although it may have limited peripheral visibility in eyes with small pupils or early lens opacities [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Additionally, the quadrant-based assessment offers a clear and reproducible comparison framework but does not capture granular variation within quadrants. Future work using finer topographic mapping or automated methods may provide deeper characterization.\u003c/p\u003e \u003cp\u003eDespite these limitations, the consistent association between axial elongation and superior Clarus performance in the superior nasal quadrant strengthens the reliability of this finding. Taken together, the results provide new insight into the interaction between ocular biometry and widefield imaging performance. While the Clarus 500 and Optos Daytona perform comparably across most quadrants, axial elongation and myopic ocular geometry selectively enhance Clarus performance in the superior nasal periphery, a region frequently involved in lattice degeneration and peripheral retinal tears and in which approximately 40% of rhegmatogenous retinal detachments demonstrate a break within the superior nasal quadrant [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. These observations underscore the importance of considering ocular shape in device-specific interpretation and suggest that biometric variables warrant greater attention in future widefield imaging research.\u003c/p\u003e \u003cp\u003eImportantly, beyond these nuanced biometric effects, the findings reaffirm that both the Clarus 500 and the Optos Daytona deliver robust, high-quality UWF imaging performance in routine clinical settings. Both devices reliably visualize clinically meaningful peripheral structures and can be considered effective tools for comprehensive peripheral retinal assessment, although visualization of the extreme far periphery remains inherently limited in both systems due to optical and anatomical constraints.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eOverall, the findings of this study indicate that both the Clarus 500 and the Optos Daytona provide robust and reliable widefield retinal imaging with largely comparable peripheral visualization across most quadrants. The only statistically meaningful distinction arose in the superior nasal quadrant, where longer axial length and more myopic refractive profiles favored Clarus performance, with an axial-length threshold near 23.77 mm marking the point at which this advantage became evident. Although shorter, more hyperopic eyes showed a descriptive tendency toward greater peripheral reach with the Optos Daytona, this trend did not achieve statistical significance and therefore should not be interpreted as a true performance benefit.\u003c/p\u003e \u003cp\u003eTaken together, these results underscore that device behavior in the far periphery is shaped not only by optical design but also by ocular geometry, and they highlight the value of considering axial length when interpreting or selecting widefield imaging systems. Importantly, despite these nuanced biometric effects, both devices performed strongly and consistently overall, supporting their use as dependable tools for comprehensive peripheral retinal assessment.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eAUC\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eArea under the curve\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eBCVA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eBest corrected visual acuity\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eIOL\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eIntraocular lens\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eIRMA\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eIntraretinal microvascular abnormalities\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eLOCS III\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eLens Opacities Classification System III\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eNPDR\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eNon\u0026ndash;proliferative diabetic retinopathy\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eRGB\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eRed, green, blue\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eROC\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eReceiver operating characteristic\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSD\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eStandard deviation\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eSE\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eSpherical equivalent\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv class=\"DefinitionListEntry\"\u003e \u003cdiv class=\"Term\"\u003eUWF\u003c/div\u003e \u003cdiv class=\"Description\"\u003e \u003cp\u003eUltra\u0026ndash;widefield\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003eEthics approval and consent to participate\u003c/p\u003e\n\u003cp\u003eThis study was approved by the Ethics Committee of the City of Vienna (approval number EK19-207-0919), registered at clinicaltrials.gov (NCT04255732), and conducted in accordance with the Declaration of Helsinki. Written informed consent was obtained from all participants prior to inclusion.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated and analyzed during this study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOF serves as a scientific advisor to Carl Zeiss Meditec AG, Croma, and Johnson \u0026amp; Johnson. All other authors declare no conflicts of interest.\u003c/p\u003e\n\u003cp id=\"_Toc472330566\"\u003eFunding\u0026nbsp;\u003c/p\u003e\n\u003cp id=\"_Toc472330568\"\u003eThis study was not supported by any sponsor or funder.\u003c/p\u003e\n\u003cp\u003eAuthor Contributions\u003c/p\u003e\n\u003cp\u003eCS, AF, MR: Study conception and design, image acquisition (MR), data analysis, manuscript drafting.\u003c/p\u003e\n\u003cp\u003eCS: Image evaluation, statistical analysis, data interpretation, manuscript revision.\u003c/p\u003e\n\u003cp\u003eMR, AF: Biometry acquisition, data curation, methodology support.\u003c/p\u003e\n\u003cp\u003eOF: Supervision, critical review of the manuscript, interpretation of results.\u003c/p\u003e\n\u003cp\u003eCS, AF, MR, OF: Final approval of the version to be published.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eByer NE. Lattice degeneration of the retina. Surv Ophthalmol. 1979;23(4):213\u0026ndash;48.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWilkinson CP. Evidence-based analysis of prophylactic treatment of asymptomatic retinal breaks and lattice degeneration. Ophthalmology. 2000;107(1):12\u0026ndash;5. discussion 15\u0026ndash;18.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKuhn F, Aylward B. Rhegmatogenous retinal detachment: a reappraisal of its pathophysiology and treatment. Ophthalmic Res. 2014;51(1):15\u0026ndash;31.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHirano T, Imai A, Kasamatsu H, Kakihara S, Toriyama Y, Murata T. Assessment of diabetic retinopathy using two ultra-wide-field fundus imaging systems, the Clarus(R) and Optos systems. BMC Ophthalmol. 2018;18(1):332.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuang B, Zheng C, Chen S, Liao X, Chen H. Quantifying retinal size and shape distortion in different ultra-widefield imaging systems. BMJ Open Ophthalmol 2025, 10(1).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSun Y, Chen X, Song Z, Liu T, Tao Y, Lai T, Chen Y, Li M, Qu J, Li X. Utilizing fundus images captured by two ultra-wide field imaging systems to measure diagnostic indicators and assess the grade of diabetic retinopathy. BMC Ophthalmol. 2025;25(1):72.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAzzopardi M, Gridhar S, Tsika C, Koutsocheras G, Katzakis M, Demir B, Rahman W, Heng LZ, Chong YJ, Logeswaran A. A Comparison of Ultra-Widefield Imaging Quality Obtained with Zeiss Clarus and Optos for Virtual Medical Retina Services. J Clin Med 2025, 14(10).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNagiel A, Lalane RA, Sadda SR, Schwartz SD. ULTRA-WIDEFIELD FUNDUS IMAGING: A Review of Clinical Applications and Future Trends. Retina. 2016;36(4):660\u0026ndash;78.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDomalpally A, Barrett N, Reimers J, Blodi B. Comparison of Ultra-Widefield Imaging and Standard Imaging in Assessment of Early Treatment Diabetic Retinopathy Severity Scale. Ophthalmol Sci. 2021;1(2):100029.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eStino H, Riessland S, Sedova A, Datlinger F, Sacu S, Schmidt-Erfurth U, Pollreisz A. Comparison of two ultra-widefield color-fundus imaging devices for visualization of retinal periphery and microvascular lesions in patients with early diabetic retinopathy. Sci Rep. 2022;12(1):17449.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChen A, Dang S, Chung MM, Ramchandran RS, Bessette AP, DiLoreto DA, Kleinman DM, Sridhar J, Wykoff CC, Kuriyan AE. Quantitative Comparison of Fundus Images by 2 Ultra-Widefield Fundus Cameras. Ophthalmol Retina. 2021;5(5):450\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNi S, Ng R, Bayhaqi Y, Sutter D, Ostmo S, Huang D, Young BK, Campbell JP, Jian Y. Comparative Evaluation of Field of View Across Widefield Retinal Imaging Systems. Transl Vis Sci Technol. 2025;14(11):20.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKhan M, Kovacs K, Guan I, Goldblatt N, Foulsham W, Wu A, Papakostas T, Gupta M, D'Amico DJ, Kiss S, et al. Evaluating Ultra-Widefield Imaging Utility in the Detection of Treatment-Requiring Peripheral Retinal Tears and Holes. Retina. 2024;44(1):71\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJonas JB, Panda-Jonas S, Pan Z, Xu J, Wang YX. Posterior Eye Shape in Myopia. Ophthalmol Sci. 2024;4(6):100575.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eVerkicharla PK, Mathur A, Mallen EA, Pope JM, Atchison DA. Eye shape and retinal shape, and their relation to peripheral refraction. Ophthalmic Physiol Opt. 2012;32(3):184\u0026ndash;99.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXu F, Hu X, Wang Y, Wei R, Yu Y, Peng Y, Li M, Wu H. The Specificity Rates of Clarus 500 Ultra-Wide-Field Retinal Imaging for Detecting Peripheral Retinal Lesions in Medium-to-High Myopia Eyes. Ophthalmic Res. 2025;68(1):352\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChylack LT Jr., Wolfe JK, Singer DM, Leske MC, Bullimore MA, Bailey IL, Friend J, McCarthy D, Wu SY. The Lens Opacities Classification System III. The Longitudinal Study of Cataract Study Group. Arch Ophthalmol. 1993;111(6):831\u0026ndash;6.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShunmugam M, Shah AN, Hysi PG, Williamson TH. The pattern and distribution of retinal breaks in eyes with rhegmatogenous retinal detachment. Am J Ophthalmol. 2014;157(1):221\u0026ndash;e226221.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-ophthalmology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"boph","sideBox":"Learn more about [BMC Ophthalmology](http://bmcophthalmol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/boph","title":"BMC Ophthalmology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Ultra-widefield imaging, Peripheral retina, Ocular biometry, Axial length","lastPublishedDoi":"10.21203/rs.3.rs-8369016/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8369016/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eThe purpose was to compare the Clarus 500 and Optos Daytona widefield imaging systems with respect to the farthest clinically assessable peripheral retinal structure in each quadrant, and to evaluate whether ocular biometry, particularly axial length and spherical equivalent, influences device specific widefield performance.\u003c/p\u003e\u003ch2\u003eMethods\u003c/h2\u003e \u003cp\u003eTwenty-six eyes underwent same day widefield imaging with Clarus 500 (Zeiss Meditec AG, Jena, Germany) and Optos Daytona (Optos plc, Dunfermline, UK). For each quadrant, the most peripheral anatomically interpretable structure was identified, and device differences were analyzed using McNemar tests. Associations with axial length and spherical equivalent, were evaluated using Mann-Whitney U tests and univariate and multivariate logistic regression. Receiver operating characteristic analysis was performed to assess the predictive value of axial length and to determine the optimal cutoff for device superiority.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eBoth widefield systems showed similar performance in the superior temporal, inferior temporal, and inferior nasal quadrants with no statistically significant differences. In the superior nasal quadrant, however, eyes in which Clarus reached farther had significantly longer axial length (23.97\u0026thinsp;\u0026plusmn;\u0026thinsp;1.62 mm versus 22.53\u0026thinsp;\u0026plusmn;\u0026thinsp;0.94 mm, p\u0026thinsp;=\u0026thinsp;0.016) and a more myopic spherical equivalent (\u0026minus;\u0026thinsp;2.05\u0026thinsp;\u0026plusmn;\u0026thinsp;4.52 D versus +\u0026thinsp;2.69\u0026thinsp;\u0026plusmn;\u0026thinsp;2.56 D, p\u0026thinsp;=\u0026thinsp;0.019). Axial length significantly predicted Clarus superiority in univariate regression (odds ratio 2.39, p\u0026thinsp;=\u0026thinsp;0.033). Receiver operating characteristic analysis demonstrated good discriminatory ability of axial length with an area under the curve of 0.782 and an optimal cutoff of 23.77 mm. Shorter and hyperopic eyes showed a tendency toward greater peripheral reach with Optos, although this trend did not achieve statistical significance.\u003c/p\u003e\u003ch2\u003eConclusion\u003c/h2\u003e \u003cp\u003eThe Clarus 500 and Optos Daytona provide comparable peripheral visualization in most retinal quadrants. Device differences become apparent in the superior nasal quadrant, where axial elongation and myopic ocular geometry enhance Clarus performance, while no statistically supported advantage for Optos is observed in shorter or hyperopic eyes. These findings underscore the relevance of ocular biometry in widefield retinal imaging and support individualized device selection in patients with myopic anatomy. Overall, both devices demonstrated robust and reliable performance, providing high quality widefield imaging suitable for comprehensive peripheral retinal assessment.\u003c/p\u003e","manuscriptTitle":"Influence of ocular biometry on peripheral retinal visualization: A comparative study of Clarus and Optos widefield imaging systems","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-12 06:02:36","doi":"10.21203/rs.3.rs-8369016/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-01-30T05:47:44+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-25T16:31:00+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-10T00:53:44+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-01-09T20:31:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"3485628340361549433317431148792401379","date":"2026-01-07T16:42:56+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"9011867485044217573104908114898416272","date":"2026-01-07T08:27:19+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"325851656519511701770872446204069128793","date":"2026-01-07T07:46:49+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-01-07T07:13:42+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2025-12-17T09:07:29+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-12-17T02:05:40+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-12-17T02:05:30+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Ophthalmology","date":"2025-12-15T17:44:54+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-ophthalmology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"boph","sideBox":"Learn more about [BMC Ophthalmology](http://bmcophthalmol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/boph","title":"BMC Ophthalmology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"23770467-042f-41ff-935e-b1bffe3f2edd","owner":[],"postedDate":"January 12th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-04-13T16:06:45+00:00","versionOfRecord":{"articleIdentity":"rs-8369016","link":"https://doi.org/10.1186/s12886-026-04782-0","journal":{"identity":"bmc-ophthalmology","isVorOnly":false,"title":"BMC Ophthalmology"},"publishedOn":"2026-04-11 15:58:52","publishedOnDateReadable":"April 11th, 2026"},"versionCreatedAt":"2026-01-12 06:02:36","video":"","vorDoi":"10.1186/s12886-026-04782-0","vorDoiUrl":"https://doi.org/10.1186/s12886-026-04782-0","workflowStages":[]},"version":"v1","identity":"rs-8369016","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8369016","identity":"rs-8369016","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}