New findings on the unique curvature region in the posterior eye using widefield OCT

New findings on the unique curvature region in the posterior eye using widefield OCT | 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 Article New findings on the unique curvature region in the posterior eye using widefield OCT Takahiro Hiraoka, Masato Tamura, Yoshikiyo Moriguchi, Riku Kuji, and 7 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4371061/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract This study aimed to explore the curvature distribution in the posterior eye among school-aged children using distortion-corrected optical coherence tomography (OCT) images and its relationship with biometric variables and choroidal vascular parameters. We conducted a prospective, observational, cross-sectional study involving 88 children aged 6 to 15 years. After comprehensive ocular examinations, widefield OCT volumes with a 68×68 degrees were captured utilizing a high-speed, wide-field SS-OCT prototype system. The distortion of the captured OCT volume was geometricallycorrected, and Gaussian curvature maps were derived from Bruch’s membrane segmentation lines. The mean curvature was assessed across four square regions of 19×19 degrees each, where axial length (AL), refractive error, age, and choroidal thickness (ChT) were statistically analyzed. Additionally, the entry site of the long posterior ciliary artery (LPCA) into the choroid were assessed from the same OCT volume. Analysis of 169 OCT images demonstrated bilateral symmetry in choroidal vascular patterns and posterior eye curvature. Mean curvature exhibited asignificant correlation with AL, refractive error, and ChT in the superior, macular, and inferior regions. Conversely, the temporal region showed a weak negative correlation. Notably, a local maximum curvature point was commonly observed in the temporal region for the first time in this study, suggesting a potential reversal of correlation in this area. The rationale for this observation remains unclear; however, the proximity of the local maximum curvature point to the long posterior ciliary artery (LPCA) entry site may suggest a link. Further investigation is necessary to elucidate the origins and implications of these findingsfor ocular development. Health sciences/Medical research Physical sciences/Optics and photonics widefield OCT Gaussian curvature posterior eye curvature axial length choroidal thickness long posterior ciliary artery Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Introduction The diversity in eyeball shape among individuals is evident [ 1 ], with morphological deviations observed in various ocular pathologies. For instance, the cornea deviates from its spherical shape and becomes more cone-like shape in keratoconus [ 2 ]. Another example is high myopia and its complications, known to form dome-shaped macula or posterior staphylomas, which are outpouchings of retina and sclera bowing towards the vitreous cavity [ 3 – 5 ]. Even natural eye growth induces subtle deformations [ 6 , 7 ]. With the accelerating increase in the prevalence of myopia, the relationship between ocular geometry and myopia progression is gaining particular attention as complementary information to the traditional axial length (AL) measurement [ 8 , 9 ]. However, compared to the anterior segment, the topography of the posterior segment of the eye is less commonly studied due to its reduced accessibility. Magnetic resonance imaging (MRI) offers three-dimensional ocular shape assessment but has resolution and cost constraints [ 6 , 7 , 10 , 11 ]. Optical techniques for posterior eye shape measurement in routine clinical practice or screening are thus sought after. Optical coherence tomography (OCT) emerges as the gold standard for visualizing posterior eye structure, providing detailed morphological information. Accordingly, many clinical studies have been conducted on the ocular geometry of myopia using OCT [ 12 – 17 ]. However, raw OCT images require distortion correction for accurate shape representation and parameter quantification. This hinders inter-patient and intra-patient longitudinal comparisons, especially in wide-angle captures. Some previous studies have attempted to correct these distortions [ 18 – 23 ]. McNabb et al. correct distortions using a “whole-eye” OCT system, and successfully generated quantitative curvature maps with intersession repeatability [ 24 , 25 ]. While simultaneous acquisition of the anterior and posterior segments of the eye using whole-eye OCT enables more accurate distortion correction, the device is not commercially available. Additionally, the polarization division technique used in whole-eye OCT systems may compromise OCT image quality by causing loss of the signal backscattered from each segment. Thorough evaluation of posterior pole morphology using recent OCT technologies is considered useful for understanding the onset and progression of myopia. However, there's a dearth of studies in children covering a wide posterior pole range. Here, we employ distortion-corrected widefield OCT to explore Gaussian curvature distribution in school-aged children's posterior eye. We also investigate its correlation with biometric variables such as AL, refractive error, and choroidal thickness. Notably, our analysis unveils a distinct morphological feature in the temporal region, possibly linked to the long posterior ciliary artery (LPCA). This paper delves into this morphological hallmark. Results Of all, one hundred sixty-nine (169) OCT images had sufficient quality to calculate the curvature without exceeding the image depth range. Figure 1 shows an example of the OCT B-frame, Bruch’s membrane (BM) contour map, and Gaussian curvature map. The Gaussian curvature map was divided into five regions, and mean curvature was investigated without the nasal section where the optic nerve head (ONH) was included. Figure 2 depicts representative max-projection OCT en-face images, choroidal layer thickness maps, and Gaussian curvature maps from twelve eyes of six subjects. Inter-subject variability and intra-subject bilateral symmetry in choroidal vascular running patterns, choroidal thickness distribution, and posterior eye curvature were observed. Additionally, thicker choroidal areas aligned with large vessels toward the vortex veins. The mean Gaussian curvature was 0.0070 ± 0.0010 (mean ± standard deviation), 0.0050 ± 0.0013, 0.0065 ± 0.0012, and 0.0062 ± 0.0010 mm -2 for the superior, macular, inferior, and temporal regions, respectively, with the macular region exhibiting the smallest (flattest) curvature (Fig. 3 ). In the superior, macular, and inferior regions, the mean curvature exhibited significant positive correlations with AL, significant negative correlations with cycloplegic spherical equivalent (SE), non-significant positive correlations with age, and significant negative correlations with mean choroidal thickness (ChT). Conversely, in the temporal region, the mean curvature showed a significant negative correlation with AL, a non-significant positive correlation with SE, a significant negative correlation with age, and a non-significant negative correlation with mean ChT (Fig. 4 ). This divergence highlights the unique trend observed in the temporal region. Interestingly, the local maximum curvature point predominantly resided within the temporal region in 157 eyes (93%), demonstrating a significant negative correlation with AL, a significant positive correlation with SE, and a significant negative correlation with age. However, no significant correlation was observed between the local maximum curvature and mean ChT (Fig. 5 ). In other words, the temporal region generally contained the local maximum curvature point among all regions examined, and the associations with biometric variables and age were notably opposite to those observed in the superior, macular, and inferior regions as depicted in Fig. 4 . Subsequently, we analyzed the geometric positioning of the local maximum curvature point relative to the fovea and the LPCA entry site into the choroid. In 87 out of 157 eyes (55%), the LPCA penetration site was identifiable on OCT en-face images of the choroid-sclera interface (CSI) slab (Fig. 6 a), with a mean distance of 5.40 ± 0.49 mm from the fovea and 1.33 ± 0.50 mm from the LPCA entry site into the choroid (Figs. 6 e, 6 f). These distances exhibited significant positive correlations with AL (Figs. 6 g, 6 h). Discussion Myopia is an ocular condition closely associated with biomechanical and dimensional changes. In this study, the distribution of the posterior eye curvature was investigated using 400 kHz, 68×68 degrees SS-OCT, and the associations with AL, SE, age, and ChT were explored in school-aged children. The Gaussian curvature map revealed bilateral symmetry between the right and left eyes and flatter curvature in the macular region compared to the adjacent areas. In a previous report on high myopia, the posterior pole was considered to have greater curvature [ 21 ]. However, in the present study, on the contrary, the macula was observed as a flatter shape with less curvature than the surrounding regions. This difference is likely due to variations in the age and myopic condition of the subject population, suggesting it might reflect the process of ocular growth. Indeed, another study reported that 20% of school-aged children had a dome-shaped macula [ 26 ]. Longitudinal studies are needed to confirm these findings. The mean curvature exhibited significant correlations with AL and SE across the superior, macular, and inferior regions. In these areas, a longer AL (indicative of higher myopia) corresponded to a steeper curvature, reflecting the elongation of the eyeball and its increased ellipticity. However, this relationship was notably absent in the temporal region, where it was entirely reversed. Also, in relation to ChT, significant negative correlations were observed in the superior, macular, and inferior regions, contrasting with the lack of significant correlation in the temporal region. This discrepancy led to an intriguing observation: the presence of a local maximum curvature point over the posterior pole located within the temporal region in most cases. Moreover, this maximum curvature point aligned closely with the extension of the line connecting the optic disc and fovea (Fig. 6 e), and it appeared proximate to the entry site of the LPCA (Fig. 6 f). While this is the first report of such findings, the exact origin of this characteristic shape remains speculative, with a potential link to LPCA suggested. Although the location does not precisely match the LPCA entry site, its proximity raises the possibility of mechanical pressure from the LPCA influencing structural features during ocular development. Additionally, variations in the rigidity of vascular walls and the sclera may have contributed to this phenomenon. Posterior ciliary arteries (PCA) circulation is the main source of blood supply in the eye [ 27 ]. Recently, topographic distribution of the short (S)-PCA entry sites into the choroid has been studied using SS-OCT but has not yet been fully understood in a large population [ 28 ]. Alternatively, other factors such as interactions between optic nerve sheaths, oblique muscles, and biomechanical scleral resistance, implicated in shaping the posterior globe in high myopia [ 5 ], could also influence the formation of the temporal local maximum curvature point. Further investigations, particularly into the topographic distribution of both SPCA and LPCA entry sites, are warranted to elucidate these findings in larger populations. The strength of the methodology lies in the utilization of high-speed 400 kHz SS-OCT. This technology allowed for the acquisition of widefield, high-density point cloud data in just 1.2 seconds, facilitated by the high-penetration depth of SS-OCT, which enabled automated CSI segmentation. To validate the technique, we assessed the variability of results from multiple imaging sessions of the same eye. It was confirmed that the variation between measurements was less than 0.00016 mm -2 , a sufficiently small margin relative to the measured values. Despite the inherent assumptions in OCT image distortion correction, including tissue refractive index parameters and estimation errors in curvature calculation, the minimal inter-measurement variability suggests the utility of Gaussian curvature as an ocular shape representation, complementing conventional AL measurements. Considering the posterior eye's curvature distribution, there's potential to optimize sampling density slightly and expand widefield imaging capabilities further. Widefield OCT not only allows for local ocular shape assessment, as demonstrated in this study, but also offers simultaneous evaluation of global ocular shape and size parameters. This broader scope opens avenues for assessing peripheral refraction [ 29 ] and investigating the relationship between global ocular shape and myopia treatment modalities such as outdoor activities, atropine eye drops, orthokeratology, and multifocal intraocular lenses [ 30 ]. In this study, we utilized the BM segmentation line to represent ocular shape. However, similar measurements can be applied to other retinochoroidal boundaries such as the inner limiting membrane, retinal pigment epithelium (RPE), and CSI, including their ratios. Hence, our technique can extend beyond myopia to assess idiopathic macular hole [ 31 ], irregular RPE curvature in age-related macular degeneration [ 32 ], and ONH shape, crucial in myopia and glaucoma [ 33 ], all central themes for future research. In conclusion, we quantitatively analyzed posterior eye curvature using distortion-corrected widefield OCT, and characterized small, localized structural deformities with micrometer-level spatial resolution. Furthermore, we observed a common local maximum curvature point in the temporal region of young, healthy eyes. Investigating its origin, we measured the geometrical distance to the LPCA site into the choroid and discussed their relationship. Further longitudinal studies are warranted to elucidate their causal connection. Methods Subjects This prospective, observational, cross-sectional study was conducted at the Yoshino Eye Clinic and approved by the Institutional Review Board of the RiverSide Clinic (Approval Number: RSC-2208RB02), adhering to the Declaration of Helsinki. Written informed consent was obtained from all parents or legal guardians of 88 children aged from 6 to 15 years (mean age: 9.9 ± 2.4 years, 44 males and 44 females) enrolled, covering bilateral eyes. Comprehensive ocular examinations, including slit-lamp examination, AL measurement (MYAH; Topcon Corp., Tokyo, Japan), anterior segment OCT (CASIA2; Tomey Corp., Nagoya, Japan), and subjective refraction assessment, were conducted. Additionally, widefield OCT imaging was performed under cycloplegic conditions induced by two drops of 1% cyclopentolate hydrochloride (Cyplegin® 1% ophthalmic solution; Santen Pharmaceutical Co., Ltd., Osaka, Japan) administered at 10-minute intervals. OCT measurements In this study, we utilized a high-speed and wide-field SS-OCT prototype system (Topcon Corp., Tokyo, Japan). Operating at a wavelength-tunable laser with a scanning rate of 400,000 A-scan/s in the 1-µm wavelength region, it offered lateral and axial resolutions of approximately 21 and 8.8 µm (full-width-at-half-maximum) in tissue, respectively. The system captured a macular-centered three-dimensional OCT volume with a 68×68 degrees apparent field-of-view and a 512×512 sampling resolution in just 1.2 seconds. With a depth imaging range of 5.3 mm in tissue, axial motion appearing in the slow scan direction was corrected using intersections with vertical lines scanned immediately after completing the horizontal raster scan. This correction involved frame shift and rotation to maximize cross-correlation at each corresponding A-line. Subsequently, data captured by the prototype SS-OCT underwent post-processing using custom-made software. Distortion correction To analyze the true posterior eye shape, we utilized a ray-tracing technique based on Navarro’s eye model to model the entire imaging system and correct optical distortions. Incorporating five additional subject-specific parameters—AL, corneal front curvature, corneal thickness, anterior chamber depth, and cornea vertex position relative to the imaging optics (estimated by the reference mirror position)—we calculated and recorded chief ray vectors on the retina for each scanning angle. Aligning each A-scan with these vectors, we converted the OCT volume from angular to real coordinates (degrees to millimeters). Ocular Shape analysis Utilizing distortion-corrected OCT images, we generated a two-dimensional curvature map as a numerical representation of the posterior eye structure. Initially, the BM, demarcating the retina and choroid, was automatically delineated using an edge-detection based segmentation algorithm. Local posterior eye curvature was then determined by the Gaussian curvature of the BM surface, with exclusion of an apparent field-of-view of 8 degrees diameter region around the ONH from the analysis. Mean curvature was evaluated in four regions centered on the fovea (superior, macular, inferior, and temporal), and Pearson’s correlation was employed to assess the relationship between mean curvature within each region and biometric variables, including AL, SE, age, and ChT. LPCA analysis. The temporal LPCA entry into the choroid was pinpointed on the OCT en-face image of the CSI, recognized as the origin of a tortuous vessel extending toward the iris. We assessed the location of the maximum Gaussian curvature within the temporal region by measuring its distance from both the fovea and the LPCA entry point into the choroid. Repeatability assessment To evaluate the repeatability of curvature measurements, three consecutive OCT measurements were performed on each of six eyes from three healthy subjects. The unbiased standard deviations of the mean curvature were 0.00013, 0.000039, 0.000037, and 0.00016 mm − 2 for the superior, macular, inferior, and temporal regions, respectively. These variations ranged from 1 to 2% from the measured curvatures, with intraclass coefficients of 0.97 to 1, indicating almost perfect repeatability. Declarations Author contributions statement T.H. and Y.M. designed the study. T.H., M.T., Y.M., T.M. prepared the manuscript. M.T., Y.M., R.K., T.M. prepared the device, and Y.T., K.Y. collected the clinical data. M.A., Y.S., K.Y., T.M. and T.O. supervised the research. All authors reviewed and agreed with the manuscript. Additional information Competing interests: Tetsuro Oshika received research support from Topcon Corp. M.T., Y.M., R.K., T.M., and M.A. are employees of Topcon Corp. Author Contribution T.H. and Y.M. designed the study. T.H., M.T., Y.M., T.M. prepared the manuscript. M.T., Y.M., R.K., T.M. prepared the device, and Y.T., K.Y. collected the clinical data. M.A., Y.S., K.Y., T.M. and T.O. supervised the research. All authors reviewed and agreed with the manuscript. Acknowledgement We thank Drs. Asaki Suzaki and Keiji Sugimoto of Menicon Co., Ltd. for their support of this study. Takahiro Hiraoka reports that this work was supported by JSPS KAKENHI Grant Number 20K09783. Data Availability The datasets used and analyzed during the current study are available from the corresponding author on reasonable request. References Verkicharla, P. K., Mathur, A., Mallen, E. A., Pope, J. M. & Atchison, D. A. Eye shape and retinal shape, and their relation to peripheral refraction. Ophthalmic. Physiol. Opt. 32 , 184–199 (2012). https://doi.org/10.1111/j.1475-1313.2012.00906.x Santodomingo-Rubido, J., Carracedo, G., Suzaki, A., Villa-Collar, C., Vincent, S. J. & Wolffsohn, J. S. Keratoconus: An updated review. Contact Lens Anterior Eye 45 , 101559 (2022). https://doi.org/10.1016/j.clae.2021.101559 Guo, X., Xiao, O, Chen, Y., Wu, H., Chen, L., Morgan, I. G., He, M. 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Rep. 13 , 15367 (2023). https://doi.org/10.1038/s41598-023-42509-z Cheung, R., Trinh, M., Tee, Y. G. & Nivison-Smith, L. RPE curvature can screen for early and intermediate AMD. Invest. Ophthalmol. Vis. Sci. 65 (2), 2 (2024). https://doi.org/10.1167/iovs.65.2.2 Burgoyne, C. F., Wang, Y. X., Jeoung, J. W., Hong, S., Gardiner, S., Reynaud, J., Fortune, B., Girard, M. J. A., Sharpe, G., Nicolela, M., Chauhan, B. C. & Yang, H. OCT optic nerve head morphology in myopia II: peri-neural canal scleral bowing and choroidal thickness in high myopia - an American Ophthalmological Society Thesis. Am. J. Ophthalmol. 252 , 225–252 (2023). https://doi.org/10.1016/j.ajo.2023.03.002 Additional Declarations No competing interests reported. Supplementary Files dataset1.xlsx dataset2.xlsx dataset3.xlsx Cite Share Download PDF Status: Posted Version 1 posted 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4371061","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":304749154,"identity":"eaece181-5633-47d0-8547-78a9f9dba9e3","order_by":0,"name":"Takahiro Hiraoka","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABDklEQVRIiWNgGAWjYDACCcYGIJnAwM/AYADiGzBIQCSYcenggWmRbACqPkCcFjCVwGBwAE0LTmAv3dz24UdFmrzxtcMbmD/8OWxscLv5AcOPGgZ2c1y2yBxsntlzJsdw2+20AoaDbYfNDO4cM2DsOcbAbNmAy2GJzQy8bRWM227nGDAcbDhsY3AjwYCBt4GBGehUnFoY/7ZV2G+eDdRy4A9IS/oHxr8EtDDztuUkbpAGaWEDOuxGjgEzXltuALXInElLngH0y4GzbenGknfOFByWOSaB0y/sM9IfM76pSLbtn5288UHFH2vDvtvtGx++qbFJxhViKOAAEkMi2YAYLSjAjnQto2AUjIJRMEwBALKiXu4DfKXCAAAAAElFTkSuQmCC","orcid":"","institution":"University of Tsukuba","correspondingAuthor":true,"prefix":"","firstName":"Takahiro","middleName":"","lastName":"Hiraoka","suffix":""},{"id":304749155,"identity":"783a5d75-11a5-4061-8ece-374845494bcc","order_by":1,"name":"Masato Tamura","email":"","orcid":"","institution":"Topcon Corporation","correspondingAuthor":false,"prefix":"","firstName":"Masato","middleName":"","lastName":"Tamura","suffix":""},{"id":304749156,"identity":"79359842-e151-440f-ba14-eadad64034c8","order_by":2,"name":"Yoshikiyo Moriguchi","email":"","orcid":"","institution":"Topcon Corporation","correspondingAuthor":false,"prefix":"","firstName":"Yoshikiyo","middleName":"","lastName":"Moriguchi","suffix":""},{"id":304749157,"identity":"86dc4e48-f7c9-49d2-8167-b84e9d19241f","order_by":3,"name":"Riku Kuji","email":"","orcid":"","institution":"Topcon Corporation","correspondingAuthor":false,"prefix":"","firstName":"Riku","middleName":"","lastName":"Kuji","suffix":""},{"id":304749158,"identity":"8db970f2-3211-403b-996a-43af30f4818d","order_by":4,"name":"Toshihiro Mino","email":"","orcid":"","institution":"Topcon Corporation","correspondingAuthor":false,"prefix":"","firstName":"Toshihiro","middleName":"","lastName":"Mino","suffix":""},{"id":304749159,"identity":"fbcac5d1-fc10-49c0-9e00-05f163f4c03d","order_by":5,"name":"Masahiro Akiba","email":"","orcid":"","institution":"Topcon Corporation","correspondingAuthor":false,"prefix":"","firstName":"Masahiro","middleName":"","lastName":"Akiba","suffix":""},{"id":304749160,"identity":"c5d145b5-45a0-493c-ad7a-a2716bd3a910","order_by":6,"name":"Yosuke Takahashi","email":"","orcid":"","institution":"Yoshino Eye Clinic","correspondingAuthor":false,"prefix":"","firstName":"Yosuke","middleName":"","lastName":"Takahashi","suffix":""},{"id":304749161,"identity":"681b74ab-b8c6-4443-92fb-0c88b44ae6e8","order_by":7,"name":"Kenichi Yoshino","email":"","orcid":"","institution":"Yoshino Eye Clinic","correspondingAuthor":false,"prefix":"","firstName":"Kenichi","middleName":"","lastName":"Yoshino","suffix":""},{"id":304749162,"identity":"2f07dfb7-ab37-444d-9e27-f325ba5b2600","order_by":8,"name":"Yoshimi Sugiura","email":"","orcid":"","institution":"University of Tsukuba","correspondingAuthor":false,"prefix":"","firstName":"Yoshimi","middleName":"","lastName":"Sugiura","suffix":""},{"id":304749163,"identity":"acd624c4-400e-4e22-b146-1297f8f5080f","order_by":9,"name":"Toshifumi Mihashi","email":"","orcid":"","institution":"Teikyo University","correspondingAuthor":false,"prefix":"","firstName":"Toshifumi","middleName":"","lastName":"Mihashi","suffix":""},{"id":304749164,"identity":"f8c1e7dc-7f69-4d6d-88f8-f96c45e6fbe8","order_by":10,"name":"Tetsuro Oshika","email":"","orcid":"","institution":"University of Tsukuba","correspondingAuthor":false,"prefix":"","firstName":"Tetsuro","middleName":"","lastName":"Oshika","suffix":""}],"badges":[],"createdAt":"2024-05-05 09:24:39","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4371061/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4371061/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":57036241,"identity":"b314611a-3c88-41d9-af51-c40223c2986a","added_by":"auto","created_at":"2024-05-23 18:38:53","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":131942,"visible":true,"origin":"","legend":"\u003cp\u003e(a) A distortion-corrected OCT B-frame across the fovea. BM segmentation line colored by Gaussian curvature is superimposed in the image. (b) Three-dimensional view of the distortion-corrected BM surface. (c) A Gaussian curvature map of the posterior eye at a field of view of 57 × 57 degrees. Region around the ONH was excluded from the analysis.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4371061/v1/6ec4490b86eb4b58c0da3c35.jpg"},{"id":57036249,"identity":"082049c7-efef-44dc-b678-bca932ffe2aa","added_by":"auto","created_at":"2024-05-23 18:38:53","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":141105,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative results from 12 eyes of 6 participants. Bilateral symmetries were observed in (a) choroidal vessel running pattern in OCT en-face images, (b) choroidal thickness maps, and (c) Gaussian curvature maps.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4371061/v1/b265d5e351cd195abf76cbef.jpg"},{"id":57036242,"identity":"6f611a05-6192-4c10-bdc5-23ea00ddfe6f","added_by":"auto","created_at":"2024-05-23 18:38:53","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":47551,"visible":true,"origin":"","legend":"\u003cp\u003eMean Gaussian curvature in each region. The mean Gaussian curvature was 0.0070 ± 0.0010, 0.0050 ± 0.0013, 0.0065 ± 0.0012, and 0.0062 ± 0.0010 mm\u003csup\u003e-2\u003c/sup\u003e for the superior, macular, inferior, and temporal regions, respectively, showing the smallest (flattest) curvature in the macular region.\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4371061/v1/b8c83746d87feab4187b29a0.jpg"},{"id":57036244,"identity":"e5470cff-dd9b-4182-89c9-94d45300a88c","added_by":"auto","created_at":"2024-05-23 18:38:53","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":156492,"visible":true,"origin":"","legend":"\u003cp\u003eScatter plots of mean Gaussian curvature as a function of AL, SE, Age, and mean ChT in the superior, macular, inferior, and temporal region. The solid line represents a significant correlation for the approximate straight line, while the dashed line indicates a non-significant correlation.\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4371061/v1/d3dbd5617b0df0af13154498.jpg"},{"id":57036246,"identity":"198184b3-58d4-41b7-999d-cf38f358eeb9","added_by":"auto","created_at":"2024-05-23 18:38:53","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":125429,"visible":true,"origin":"","legend":"\u003cp\u003eScatter plots of the local maximum curvature in the temporal region as a function of (a) AL, (b) SE, (c) age, and (d) mean ChT. The solid line represents a significant correlation for the approximate straight line, while the dashed line indicates a non-significant correlation.\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4371061/v1/30b31533c2c9d02a5730654f.jpg"},{"id":57036247,"identity":"1bfd952a-bf9c-4435-a207-2a78b152217d","added_by":"auto","created_at":"2024-05-23 18:38:53","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":260741,"visible":true,"origin":"","legend":"\u003cp\u003e(a) OCT en-face image at CSI. (b) Gaussian curvature map. (c) Overlaid image of (a) and (b). (d) OCT B-scan image corresponding to the horizontal line in (a). The temporal LPCA entry site into the choroid defined as the root of a tortuous vessel is indicated by red arrows. Geometrical location of the local maximum point of the curvature in the temporal region is identified as the distance from the fovea (e), and temporal LPCA entry site into the choroid (f). These showed significant correlations with AL (g, h). The solid line represents a significant correlation for the approximate straight line, while the dashed line indicates a non-significant correlation.\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4371061/v1/1d8a5fb012532b8d033b02d0.jpg"},{"id":58212874,"identity":"fa9b11e9-5cd0-4a2a-a8ba-952de41cf50e","added_by":"auto","created_at":"2024-06-12 13:59:23","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1267425,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4371061/v1/4baf8fc2-e916-493b-b0e2-1f5430b940a2.pdf"},{"id":57036245,"identity":"61ce1f3c-f77c-43e3-a44a-8f08a07caf27","added_by":"auto","created_at":"2024-05-23 18:38:53","extension":"xlsx","order_by":8,"title":"","display":"","copyAsset":false,"role":"supplement","size":231732,"visible":true,"origin":"","legend":"","description":"","filename":"dataset1.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4371061/v1/f63f1cc206132d6090ce1d6d.xlsx"},{"id":57036248,"identity":"1ae1d45b-4e2c-462d-8664-45160881e954","added_by":"auto","created_at":"2024-05-23 18:38:53","extension":"xlsx","order_by":9,"title":"","display":"","copyAsset":false,"role":"supplement","size":92562,"visible":true,"origin":"","legend":"","description":"","filename":"dataset2.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4371061/v1/0e519a7a5f4904c22a0e6ab0.xlsx"},{"id":57036250,"identity":"81cb84b4-cdd0-480b-90c1-4d5f886117d7","added_by":"auto","created_at":"2024-05-23 18:38:53","extension":"xlsx","order_by":10,"title":"","display":"","copyAsset":false,"role":"supplement","size":25289,"visible":true,"origin":"","legend":"","description":"","filename":"dataset3.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-4371061/v1/7d4eeb7b362e167a4475f5d5.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"New findings on the unique curvature region in the posterior eye using widefield OCT","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe diversity in eyeball shape among individuals is evident [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e], with morphological deviations observed in various ocular pathologies. For instance, the cornea deviates from its spherical shape and becomes more cone-like shape in keratoconus [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Another example is high myopia and its complications, known to form dome-shaped macula or posterior staphylomas, which are outpouchings of retina and sclera bowing towards the vitreous cavity [\u003cspan additionalcitationids=\"CR4\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Even natural eye growth induces subtle deformations [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. With the accelerating increase in the prevalence of myopia, the relationship between ocular geometry and myopia progression is gaining particular attention as complementary information to the traditional axial length (AL) measurement [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHowever, compared to the anterior segment, the topography of the posterior segment of the eye is less commonly studied due to its reduced accessibility. Magnetic resonance imaging (MRI) offers three-dimensional ocular shape assessment but has resolution and cost constraints [\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]. Optical techniques for posterior eye shape measurement in routine clinical practice or screening are thus sought after.\u003c/p\u003e \u003cp\u003eOptical coherence tomography (OCT) emerges as the gold standard for visualizing posterior eye structure, providing detailed morphological information. Accordingly, many clinical studies have been conducted on the ocular geometry of myopia using OCT [\u003cspan additionalcitationids=\"CR13 CR14 CR15 CR16\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. However, raw OCT images require distortion correction for accurate shape representation and parameter quantification. This hinders inter-patient and intra-patient longitudinal comparisons, especially in wide-angle captures. Some previous studies have attempted to correct these distortions [\u003cspan additionalcitationids=\"CR19 CR20 CR21 CR22\" citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. McNabb \u003cem\u003eet al.\u003c/em\u003e correct distortions using a \u0026ldquo;whole-eye\u0026rdquo; OCT system, and successfully generated quantitative curvature maps with intersession repeatability [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. While simultaneous acquisition of the anterior and posterior segments of the eye using whole-eye OCT enables more accurate distortion correction, the device is not commercially available. Additionally, the polarization division technique used in whole-eye OCT systems may compromise OCT image quality by causing loss of the signal backscattered from each segment.\u003c/p\u003e \u003cp\u003eThorough evaluation of posterior pole morphology using recent OCT technologies is considered useful for understanding the onset and progression of myopia. However, there's a dearth of studies in children covering a wide posterior pole range. Here, we employ distortion-corrected widefield OCT to explore Gaussian curvature distribution in school-aged children's posterior eye. We also investigate its correlation with biometric variables such as AL, refractive error, and choroidal thickness. Notably, our analysis unveils a distinct morphological feature in the temporal region, possibly linked to the long posterior ciliary artery (LPCA). This paper delves into this morphological hallmark.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eOf all, one hundred sixty-nine (169) OCT images had sufficient quality to calculate the curvature without exceeding the image depth range. Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e shows an example of the OCT B-frame, Bruch\u0026rsquo;s membrane (BM) contour map, and Gaussian curvature map. The Gaussian curvature map was divided into five regions, and mean curvature was investigated without the nasal section where the optic nerve head (ONH) was included. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e depicts representative max-projection OCT en-face images, choroidal layer thickness maps, and Gaussian curvature maps from twelve eyes of six subjects. Inter-subject variability and intra-subject bilateral symmetry in choroidal vascular running patterns, choroidal thickness distribution, and posterior eye curvature were observed. Additionally, thicker choroidal areas aligned with large vessels toward the vortex veins.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe mean Gaussian curvature was 0.0070\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0010 (mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation), 0.0050\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0013, 0.0065\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0012, and 0.0062\u0026thinsp;\u0026plusmn;\u0026thinsp;0.0010 mm\u003csup\u003e-2\u003c/sup\u003e for the superior, macular, inferior, and temporal regions, respectively, with the macular region exhibiting the smallest (flattest) curvature (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). In the superior, macular, and inferior regions, the mean curvature exhibited significant positive correlations with AL, significant negative correlations with cycloplegic spherical equivalent (SE), non-significant positive correlations with age, and significant negative correlations with mean choroidal thickness (ChT). Conversely, in the temporal region, the mean curvature showed a significant negative correlation with AL, a non-significant positive correlation with SE, a significant negative correlation with age, and a non-significant negative correlation with mean ChT (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e). This divergence highlights the unique trend observed in the temporal region.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eInterestingly, the local maximum curvature point predominantly resided within the temporal region in 157 eyes (93%), demonstrating a significant negative correlation with AL, a significant positive correlation with SE, and a significant negative correlation with age. However, no significant correlation was observed between the local maximum curvature and mean ChT (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). In other words, the temporal region generally contained the local maximum curvature point among all regions examined, and the associations with biometric variables and age were notably opposite to those observed in the superior, macular, and inferior regions as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSubsequently, we analyzed the geometric positioning of the local maximum curvature point relative to the fovea and the LPCA entry site into the choroid. In 87 out of 157 eyes (55%), the LPCA penetration site was identifiable on OCT en-face images of the choroid-sclera interface (CSI) slab (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ea), with a mean distance of 5.40\u0026thinsp;\u0026plusmn;\u0026thinsp;0.49 mm from the fovea and 1.33\u0026thinsp;\u0026plusmn;\u0026thinsp;0.50 mm from the LPCA entry site into the choroid (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ee, \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ef). These distances exhibited significant positive correlations with AL (Figs.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eg, \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eh).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eMyopia is an ocular condition closely associated with biomechanical and dimensional changes. In this study, the distribution of the posterior eye curvature was investigated using 400 kHz, 68\u0026times;68 degrees SS-OCT, and the associations with AL, SE, age, and ChT were explored in school-aged children. The Gaussian curvature map revealed bilateral symmetry between the right and left eyes and flatter curvature in the macular region compared to the adjacent areas. In a previous report on high myopia, the posterior pole was considered to have greater curvature [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. However, in the present study, on the contrary, the macula was observed as a flatter shape with less curvature than the surrounding regions. This difference is likely due to variations in the age and myopic condition of the subject population, suggesting it might reflect the process of ocular growth. Indeed, another study reported that 20% of school-aged children had a dome-shaped macula [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Longitudinal studies are needed to confirm these findings.\u003c/p\u003e \u003cp\u003eThe mean curvature exhibited significant correlations with AL and SE across the superior, macular, and inferior regions. In these areas, a longer AL (indicative of higher myopia) corresponded to a steeper curvature, reflecting the elongation of the eyeball and its increased ellipticity. However, this relationship was notably absent in the temporal region, where it was entirely reversed. Also, in relation to ChT, significant negative correlations were observed in the superior, macular, and inferior regions, contrasting with the lack of significant correlation in the temporal region. This discrepancy led to an intriguing observation: the presence of a local maximum curvature point over the posterior pole located within the temporal region in most cases. Moreover, this maximum curvature point aligned closely with the extension of the line connecting the optic disc and fovea (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ee), and it appeared proximate to the entry site of the LPCA (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003ef). While this is the first report of such findings, the exact origin of this characteristic shape remains speculative, with a potential link to LPCA suggested. Although the location does not precisely match the LPCA entry site, its proximity raises the possibility of mechanical pressure from the LPCA influencing structural features during ocular development. Additionally, variations in the rigidity of vascular walls and the sclera may have contributed to this phenomenon. Posterior ciliary arteries (PCA) circulation is the main source of blood supply in the eye [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Recently, topographic distribution of the short (S)-PCA entry sites into the choroid has been studied using SS-OCT but has not yet been fully understood in a large population [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Alternatively, other factors such as interactions between optic nerve sheaths, oblique muscles, and biomechanical scleral resistance, implicated in shaping the posterior globe in high myopia [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], could also influence the formation of the temporal local maximum curvature point. Further investigations, particularly into the topographic distribution of both SPCA and LPCA entry sites, are warranted to elucidate these findings in larger populations.\u003c/p\u003e \u003cp\u003eThe strength of the methodology lies in the utilization of high-speed 400 kHz SS-OCT. This technology allowed for the acquisition of widefield, high-density point cloud data in just 1.2 seconds, facilitated by the high-penetration depth of SS-OCT, which enabled automated CSI segmentation. To validate the technique, we assessed the variability of results from multiple imaging sessions of the same eye. It was confirmed that the variation between measurements was less than 0.00016 mm\u003csup\u003e-2\u003c/sup\u003e, a sufficiently small margin relative to the measured values. Despite the inherent assumptions in OCT image distortion correction, including tissue refractive index parameters and estimation errors in curvature calculation, the minimal inter-measurement variability suggests the utility of Gaussian curvature as an ocular shape representation, complementing conventional AL measurements. Considering the posterior eye's curvature distribution, there's potential to optimize sampling density slightly and expand widefield imaging capabilities further. Widefield OCT not only allows for local ocular shape assessment, as demonstrated in this study, but also offers simultaneous evaluation of global ocular shape and size parameters. This broader scope opens avenues for assessing peripheral refraction [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] and investigating the relationship between global ocular shape and myopia treatment modalities such as outdoor activities, atropine eye drops, orthokeratology, and multifocal intraocular lenses [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn this study, we utilized the BM segmentation line to represent ocular shape. However, similar measurements can be applied to other retinochoroidal boundaries such as the inner limiting membrane, retinal pigment epithelium (RPE), and CSI, including their ratios. Hence, our technique can extend beyond myopia to assess idiopathic macular hole [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e], irregular RPE curvature in age-related macular degeneration [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], and ONH shape, crucial in myopia and glaucoma [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e], all central themes for future research.\u003c/p\u003e \u003cp\u003eIn conclusion, we quantitatively analyzed posterior eye curvature using distortion-corrected widefield OCT, and characterized small, localized structural deformities with micrometer-level spatial resolution. Furthermore, we observed a common local maximum curvature point in the temporal region of young, healthy eyes. Investigating its origin, we measured the geometrical distance to the LPCA site into the choroid and discussed their relationship. Further longitudinal studies are warranted to elucidate their causal connection.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003eSubjects\u003c/h2\u003e\n \u003cp\u003eThis prospective, observational, cross-sectional study was conducted at the Yoshino Eye Clinic and approved by the Institutional Review Board of the RiverSide Clinic (Approval Number: RSC-2208RB02), adhering to the Declaration of Helsinki. Written informed consent was obtained from all parents or legal guardians of 88 children aged from 6 to 15 years (mean age: 9.9\u0026thinsp;\u0026plusmn;\u0026thinsp;2.4 years, 44 males and 44 females) enrolled, covering bilateral eyes. Comprehensive ocular examinations, including slit-lamp examination, AL measurement (MYAH; Topcon Corp., Tokyo, Japan), anterior segment OCT (CASIA2; Tomey Corp., Nagoya, Japan), and subjective refraction assessment, were conducted. Additionally, widefield OCT imaging was performed under cycloplegic conditions induced by two drops of 1% cyclopentolate hydrochloride (Cyplegin\u0026reg; 1% ophthalmic solution; Santen Pharmaceutical Co., Ltd., Osaka, Japan) administered at 10-minute intervals.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003eOCT measurements\u003c/h2\u003e\n \u003cp\u003eIn this study, we utilized a high-speed and wide-field SS-OCT prototype system (Topcon Corp., Tokyo, Japan). Operating at a wavelength-tunable laser with a scanning rate of 400,000 A-scan/s in the 1-\u0026micro;m wavelength region, it offered lateral and axial resolutions of approximately 21 and 8.8 \u0026micro;m (full-width-at-half-maximum) in tissue, respectively. The system captured a macular-centered three-dimensional OCT volume with a 68\u0026times;68 degrees apparent field-of-view and a 512\u0026times;512 sampling resolution in just 1.2 seconds. With a depth imaging range of 5.3 mm in tissue, axial motion appearing in the slow scan direction was corrected using intersections with vertical lines scanned immediately after completing the horizontal raster scan. This correction involved frame shift and rotation to maximize cross-correlation at each corresponding A-line. Subsequently, data captured by the prototype SS-OCT underwent post-processing using custom-made software.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\n \u003ch2\u003eDistortion correction\u003c/h2\u003e\n \u003cp\u003eTo analyze the true posterior eye shape, we utilized a ray-tracing technique based on Navarro\u0026rsquo;s eye model to model the entire imaging system and correct optical distortions. Incorporating five additional subject-specific parameters\u0026mdash;AL, corneal front curvature, corneal thickness, anterior chamber depth, and cornea vertex position relative to the imaging optics (estimated by the reference mirror position)\u0026mdash;we calculated and recorded chief ray vectors on the retina for each scanning angle. Aligning each A-scan with these vectors, we converted the OCT volume from angular to real coordinates (degrees to millimeters).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003eOcular Shape analysis\u003c/h2\u003e\n \u003cp\u003eUtilizing distortion-corrected OCT images, we generated a two-dimensional curvature map as a numerical representation of the posterior eye structure. Initially, the BM, demarcating the retina and choroid, was automatically delineated using an edge-detection based segmentation algorithm. Local posterior eye curvature was then determined by the Gaussian curvature of the BM surface, with exclusion of an apparent field-of-view of 8 degrees diameter region around the ONH from the analysis. Mean curvature was evaluated in four regions centered on the fovea (superior, macular, inferior, and temporal), and Pearson\u0026rsquo;s correlation was employed to assess the relationship between mean curvature within each region and biometric variables, including AL, SE, age, and ChT.\u003c/p\u003e\n \u003cp\u003e\u003cstrong\u003eLPCA analysis.\u003c/strong\u003e\u003c/p\u003e\n \u003cp\u003eThe temporal LPCA entry into the choroid was pinpointed on the OCT en-face image of the CSI, recognized as the origin of a tortuous vessel extending toward the iris. We assessed the location of the maximum Gaussian curvature within the temporal region by measuring its distance from both the fovea and the LPCA entry point into the choroid.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\n \u003ch2\u003eRepeatability assessment\u003c/h2\u003e\n \u003cp\u003eTo evaluate the repeatability of curvature measurements, three consecutive OCT measurements were performed on each of six eyes from three healthy subjects. The unbiased standard deviations of the mean curvature were 0.00013, 0.000039, 0.000037, and 0.00016 mm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e for the superior, macular, inferior, and temporal regions, respectively. These variations ranged from 1 to 2% from the measured curvatures, with intraclass coefficients of 0.97 to 1, indicating almost perfect repeatability.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor contributions statement\u003c/h2\u003e\n\u003cp\u003eT.H. and Y.M. designed the study. T.H., M.T., Y.M., T.M. prepared the manuscript. M.T., Y.M., R.K., T.M. prepared the device, and Y.T., K.Y. collected the clinical data. M.A., Y.S., K.Y., T.M. and T.O. supervised the research. All authors reviewed and agreed with the manuscript.\u003c/p\u003e\n\u003ch2\u003e\u003cstrong\u003eAdditional information\u003c/strong\u003e\u003c/h2\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTetsuro Oshika received research support from Topcon Corp. M.T., Y.M., R.K., T.M., and M.A. are employees of Topcon Corp.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eT.H. and Y.M. designed the study. T.H., M.T., Y.M., T.M. prepared the manuscript. M.T., Y.M., R.K., T.M. prepared the device, and Y.T., K.Y. collected the clinical data. M.A., Y.S., K.Y., T.M. and T.O. supervised the research. All authors reviewed and agreed with the manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eWe thank Drs. Asaki Suzaki and Keiji Sugimoto of Menicon Co., Ltd. for their support of this study. Takahiro Hiraoka reports that this work was supported by JSPS KAKENHI Grant Number 20K09783.\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eThe datasets used and analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eVerkicharla, P. 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Ophthalmol.\u003c/em\u003e\u003cstrong\u003e252\u003c/strong\u003e, 225\u0026ndash;252 (2023). https://doi.org/10.1016/j.ajo.2023.03.002\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"widefield OCT, Gaussian curvature, posterior eye curvature, axial length, choroidal thickness, long posterior ciliary artery","lastPublishedDoi":"10.21203/rs.3.rs-4371061/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4371061/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study aimed to explore the curvature distribution in the posterior eye among school-aged children using distortion-corrected optical coherence tomography (OCT) images and its relationship with biometric variables and choroidal vascular parameters. We conducted a prospective, observational, cross-sectional study involving 88 children aged 6 to 15 years. After comprehensive ocular examinations, widefield OCT volumes with a 68×68 degrees were captured utilizing a high-speed, wide-field SS-OCT prototype system. The distortion of the captured OCT volume was geometricallycorrected, and Gaussian curvature maps were derived from Bruch’s membrane segmentation lines. The mean curvature was assessed across four square regions of 19×19 degrees each, where axial length (AL), refractive error, age, and choroidal thickness (ChT) were statistically analyzed. Additionally, the entry site of the long posterior ciliary artery (LPCA) into the choroid were assessed from the same OCT volume.\u003c/p\u003e\n\u003cp\u003eAnalysis of 169 OCT images demonstrated bilateral symmetry in choroidal vascular patterns and posterior eye curvature. Mean curvature exhibited asignificant correlation with AL, refractive error, and ChT in the superior, macular, and inferior regions. Conversely, the temporal region showed a weak negative correlation. Notably, a local maximum curvature point was commonly observed in the temporal region for the first time in this study, suggesting a potential reversal of correlation in this area. The rationale for this observation remains unclear; however, the proximity of the local maximum curvature point to the long posterior ciliary artery (LPCA) entry site may suggest a link. Further investigation is necessary to elucidate the origins and implications of these findingsfor ocular development.\u003c/p\u003e","manuscriptTitle":"New findings on the unique curvature region in the posterior eye using widefield OCT","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-23 18:38:46","doi":"10.21203/rs.3.rs-4371061/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"88925c79-5eaf-4e6c-91c4-9100c4049824","owner":[],"postedDate":"May 23rd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":32174259,"name":"Health sciences/Medical research"},{"id":32174260,"name":"Physical sciences/Optics and photonics"}],"tags":[],"updatedAt":"2024-06-12T13:59:12+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-23 18:38:46","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4371061","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4371061","identity":"rs-4371061","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}