Reti̇nal and Choroi̇dal Mi̇crovascular Changes İn Hemodi̇alysi̇s and Peri̇toneal Di̇alysi̇s: A Comparati̇ve Oct and Oct-a Study

Reti̇nal and Choroi̇dal Mi̇crovascular Changes İn Hemodi̇alysi̇s and Peri̇toneal Di̇alysi̇s: A Comparati̇ve Oct and Oct-a Study | 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 Reti̇nal and Choroi̇dal Mi̇crovascular Changes İn Hemodi̇alysi̇s and Peri̇toneal Di̇alysi̇s: A Comparati̇ve Oct and Oct-a Study Binhan Aslan Akbulut, Ahmet Altıntaş, Emine Alyamaç Sukgen, Tayyibe Saler, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9360672/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 6 You are reading this latest preprint version Abstract Purpose: This study aimed to evaluate the retinal and choroidal structural parameters using optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) in patients undergoing hemodialysis (HD) and peritoneal dialysis (PD). Furthermore, it examined the impact of hemodynamic alterations associated with dialysis on ocular metrics. Methods: This prospective observational study encompassed 84 eyes from 46 patients undergoing either HD or PD. Ocular measures were conducted at two intervals based on the dialysis modality. Measurements for HD patients were taken prior to and following dialysis; for PD patients, measurements were performed post-dialysate drainage and subsequent to refilling. Comprehensive ophthalmologic assessments and OCT/OCTA imaging were performed.Statistical analyses were used to compare pre- and post-dialysis values and to evaluate differences between groups. Results: Central macular thickness (CMT) and subfoveal choroidal thickness significantly decreased after dialysis. Systolic and diastolic blood pressures also showed significant reductions. No significant changes were noted in OCTA-derived retinal microvascular metrics, including vessel density and FAZ values. A significant difference in ΔCMT was observed between the HD and PD groups. Correlation analysis indicated a moderate negative association between ΔCMT and alterations in systolic blood pressure, alongside a moderate positive correlation with the duration of dialysis. Conclusion: While most retinal microvascular parameters remained stable, changes in macular thickness differed between the dialysis modalities. These findings indicate that hemodialysis may elicit more significant short-term structural alterations in the retina than peritoneal dialysis, possibly owing to increased hemodynamic variability.OCT and OCTA could be useful, non-invasive tools for assessing small blood vessel changes in people with end-stage renal disease who are on dialysis. Key Words:Hemodialysis,Peritoneal Dialysis,OCT-A,OCT,Coroidal Thickness INTRODUCTION Chronic kidney disease (CKD) is an important public health problem worldwide, associated with increasing prevalence and high morbidity and mortality. CKD is defined as kidney damage lasting at least three months or an estimated glomerular filtration rate (eGFR) below 60 mL/min/1.73 m². According to the Kidney Disease Outcomes Quality Initiative (KDOQI) classification, CKD has five stages based on eGFR, with stage 5 representing end-stage renal disease (ESRD) and an eGFR below 15 mL/min/1.73 m² [ 1 ]. In patients with ESRD, renal replacement therapies (RRT) are required to maintain metabolic balance. The main RRT modalities include hemodialysis, peritoneal dialysis, and renal transplantation [ 2 ]. Peritoneal dialysis can be performed as continuous ambulatory peritoneal dialysis (CAPD) or automated peritoneal dialysis (APD), depending on the dialysis protocol.CKD is a systemic condition that affects multiple organs and systems, including the cardiovascular, endocrine, gastrointestinal, and nervous systems. Ocular involvement is also common, particularly in patients with underlying diseases such as diabetes mellitus and hypertension, which may lead to ocular complications including diabetic and hypertensive retinopathy [ 3 , 4 ]. Dialysis treatment induces significant systemic hemodynamic and osmotic changes, including alterations in blood pressure, plasma osmolarity, and fluid balance. These changes may influence ocular structures, particularly the retina and choroid, which are highly vascularized tissues [ 5 ]. Previous studies have suggested that dialysis may lead to measurable alterations in retinal thickness, choroidal thickness, and retinal microvascular circulation; however, the exact mechanisms and clinical implications remain incompletely understood [ 6 ]. In patients with ESRD, hemodialysis introduces unique physiological stressors that may influence ocular circulation and structure. Ultrafiltration, osmotic shifts, and fluctuations in systemic blood pressure occurring during dialysis sessions can acutely affect ocular perfusion and tissue thickness, particularly in highly vascular structures such as the choroid. Previous studies have demonstrated that hemodialysis may induce measurable changes in ocular parameters, including retinal and choroidal thickness. Recent meta-analyses have reported a modest but consistent decrease in subfoveal choroidal thickness following hemodialysis, whereas retinal thickness parameters generally show minimal acute alterations. These findings suggest that the choroidal circulation may be more sensitive to systemic hemodynamic and fluid shifts occurring during dialysis sessions [ 7 ]. Beyond these acute dialysis-related changes, chronic kidney disease has also been associated with long-term structural alterations in ocular tissues. Retinal arteriolar narrowing, progressive choroidal thinning, and thinning of the retinal nerve fiber layer (RNFL) and ganglion cell–inner plexiform layer (GCIPL) have been reported in patients with CKD. These structural changes appear to be closely related to systemic microvascular damage and are frequently exacerbated by comorbid conditions such as diabetes mellitus and hypertension [ 8 – 11 ]. Because the retinal and renal microvasculature share similar structural and autoregulatory characteristics, alterations detected in retinal and choroidal structures may reflect systemic microvascular dysfunction. Several studies have demonstrated associations between ocular structural parameters and markers of renal impairment, including decreased eGFR and increased albuminuria [ 9 – 11 ]. Consequently, ocular imaging techniques may provide valuable, non-invasive biomarkers for evaluating microvascular damage in CKD. In recent years, optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) have become widely used imaging modalities for the evaluation of retinal and choroidal structures. OCT allows detailed assessment of retinal thickness parameters such as central macular thickness (CMT) and choroidal thickness, while OCTA enables non-invasive visualization and quantitative evaluation of retinal microvasculature. These technologies provide important insights into microvascular alterations that may occur in systemic diseases such as CKD. Therefore, the present study aimed to evaluate retinal and choroidal structural parameters using OCT and OCTA in patients undergoing hemodialysis and peritoneal dialysis, and to investigate the potential effects of dialysis-related hemodynamic changes on ocular measurements. Understanding these ocular alterations may contribute to a better characterization of systemic microvascular dysfunction in patients with chronic kidney disease and may provide useful biomarkers for monitoring disease-related vascular changes. To the best of our knowledge, limited studies are comparing ocular structural parameters between hemodialysis and peritoneal dialysis using OCT and OCTA. METHODS This prospective observational study was conducted in 2021 at the Dialysis Unit of Adana City Training and Research Hospital, Türkiye. Patients undergoing hemodialysis (HD) or peritoneal dialysis (PD) who were regularly followed in the dialysis clinic were included in the study. Ophthalmologic examinations were performed at two time points according to the dialysis modality. For hemodialysis patients, ocular measurements were obtained 30 minutes before the dialysis session and 30 minutes after the completion of dialysis, both at rest. For peritoneal dialysis patients, measurements were performed 15 minutes after draining the dialysate and 2 hours after refilling the dialysate, also at rest. A total of 84 eyes from 46 patients were included in the analysis. Patients with ocular conditions that could affect retinal or choroidal measurements, such as significant media opacity, previous retinal surgery, advanced glaucoma, or retinal vascular diseases, were excluded from the study. The study adhered to the principles of the Declaration of Helsinki. Ethical approval was obtained from the Adana City Training and Research Hospital Ethics Committee (Approval No: 1358), and written informed consent was obtained from all participants. All participants underwent a comprehensive ophthalmologic examination at each visit. The examination included: Best-corrected visual acuity (BCVA) measurement using a Snellen chart and converted to logMAR for statistical analysis Slit-lamp biomicroscopic examination Intraocular pressure measurement using tonometry Dilated fundus examination Optical coherence tomography angiography (OCTA) images were obtained using the AngioVue OCTA system (Optovue Inc., Fremont, CA, USA). Macular scans were acquired using a 3×3 mm scanning protocol centered on the fovea. The following parameters were recorded from OCTA images: superficial capillary plexus (SCP) vessel density (whole, foveal, parafoveal), deep capillary plexus (DCP) vessel density (whole, foveal, parafoveal), foveal avascular zone (FAZ) area, FAZ perimeter,CMT Only OCTA images with a signal quality score of ≥ 5 (Q5) were included in the analysis. Images with poor quality or significant motion artifacts were excluded. Subfoveal choroidal thickness was measured manually on raster B-scan images obtained from the same AngioVue device (Optovue Inc., Fremont, CA, USA). Choroidal thickness was defined as the vertical distance between the outer border of the retinal pigment epithelium (RPE) and the choroid–sclera interface. Each measurement was performed three times, and the mean value of these three measurements was used for statistical analysis to reduce measurement variability. The same experienced ophthalmologist performed all OCTA image acquisitions and manual measurements to ensure measurement consistency. All statistical analyses were performed using IBM SPSS Statistics software (IBM Corp., Armonk, NY, USA). The Shapiro–Wilk test was used to evaluate the normality of the data distribution. All statistical analyses were performed using IBM SPSS Statistics software (IBM Corp., Armonk, NY, USA). Continuous variables were expressed as mean ± standard deviation (SD), while categorical variables were presented as frequencies and percentages. The Shapiro–Wilk test was used to evaluate the normality of the data distribution. Comparisons between pre-dialysis and post-dialysis measurements were performed using the Wilcoxon signed-rank test. Differences between hemodialysis and peritoneal dialysis groups were analyzed using the Mann–Whitney U test. Correlations between systemic dialysis parameters and ocular measurements were assessed using Spearman correlation analysis. p-value < 0.05 was considered statistically significant. RESULTS A total of 84 eyes from 46 patients undergoing dialysis were included in the study. Of these, 49 eyes (58.3%) belonged to patients receiving hemodialysis (HD) and 35 eyes (41.7%) belonged to patients undergoing peritoneal dialysis (PD). The mean age of the study population was 47.71 ± 12.92 years. The mean age was 47.63 ± 12.07 years in the HD group and 47.83 ± 14.20 years in the PD group. The mean body mass index (BMI) was 25.27 ± 4.16 kg/m² overall, 24.85 ± 4.43 kg/m² in HD patients, and 25.86 ± 3.74 kg/m² in PD patients. The mean dialysis session duration was 4.81 ± 0.99 hours. Session duration was 4.00 ± 0.00 hours in the HD group and 5.94 ± 0.34 hours in the PD group. The mean ultrafiltration volume was 2730.95 ± 1020.83 mL, with 3065.31 ± 1228.24 mL in HD patients and 2262.86 ± 165.98 mL in PD patients. (Table 1 ) Before dialysis, the mean CMT was 208.43 ± 17.80 µm. The mean foveal avascular zone (FAZ) area was 0.312 ± 0.121 mm², and the FAZ perimeter was 2.26 ± 0.50 mm. The mean SCP vessel density was 44.94 ± 4.79% in the whole image, 14.94 ± 6.19% in the fovea, and 48.09 ± 5.13% in the parafoveal region. For the DCP, the mean vessel density values were 50.67 ± 4.79% in the whole image, 31.31 ± 7.92% in the fovea, and 52.89 ± 5.04% in the parafoveal region. The mean subfoveal choroidal thickness was 250.90 ± 42.40 µm, and the mean best-corrected visual acuity (BCVA) was 0.081 ± 0.114 logMAR. (Table 2) After dialysis, the mean central macular thickness was 209.85 ± 17.45 µm. The mean FAZ area was 0.318 ± 0.128 mm², and the FAZ perimeter was 2.28 ± 0.54 mm. The mean SCP vessel density was 44.71 ± 5.14% in the whole image, 14.86 ± 6.22% in the fovea, and 47.64 ± 5.64% in the parafoveal region. The mean DCP vessel density values were 50.48 ± 5.16% in the whole image, 30.89 ± 7.96% in the fovea, and 52.70 ± 5.19% in the parafoveal region. The mean subfoveal choroidal thickness after dialysis was 245.68 ± 46.53 µm, and the mean BCVA was 0.075 ± 0.098 logMAR. (Table 3) Pre- and post-dialysis measurements were compared using the Wilcoxon signed-rank test. A statistically significant decrease was observed in central macular thickness after dialysis (p < 0.001). Subfoveal choroidal thickness significantly decreased following dialysis (p = 0.013). Systemic parameters also showed significant changes during dialysis. Both systolic blood pressure (p = 0.001) and diastolic blood pressure (p < 0.001) decreased significantly after dialysis. No statistically significant changes were observed in OCTA-derived retinal microvascular parameters, including SCP vessel density, DCP vessel density, FAZ area, FAZ perimeter, and BCVA (all p > 0.05). (Table 4) The changes in ocular and systemic parameters were compared between the HD and PD groups using the Mann-Whitney U test. A statistically significant difference was observed in the change in ΔCMT between the two dialysis modalities (p = 0.002).In addition, changes in systolic blood pressure (p < 0.001), diastolic blood pressure (p = 0.017), and intraocular pressure (p = 0.006) differed significantly between the groups. However, no significant differences were detected between HD and PD patients in OCTA-derived retinal microvascular parameters, including SCP vessel density, DCP vessel density, FAZ parameters, choroidal thickness, and BCVA (all p > 0.05). (Table 5) Spearman correlation analysis revealed a moderate negative correlation between ΔCMT and Δsystolic blood pressure (r = − 0.372, p < 0.001). Additionally, dialysis session duration showed a moderate positive correlation with ΔCMT (r = 0.320, p = 0.003). A weak negative correlation was observed between ultrafiltration volume and ΔDCP whole vessel density (r = − 0.239, p = 0.028). No significant correlations were found between ultrafiltration volume and other OCTA parameters (all p > 0.05). DISCUSSION The retinal and choroidal microvasculature are increasingly recognized as accessible indicators of systemic microvascular health. Because the retina shares anatomical and physiological characteristics with other end-organ microvascular beds, retinal imaging techniques such as optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) offer a unique opportunity to evaluate systemic vascular alterations in vivo. In patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD), systemic microvascular dysfunction, chronic inflammation, endothelial injury, and metabolic disturbances contribute to widespread vascular alterations that may also affect ocular circulation. Hemodialysis, while essential for removing metabolic waste products and excess fluid, exposes patients to rapid hemodynamic and osmotic fluctuations that may influence systemic and ocular circulation [ 12 ]. During a dialysis session, ultrafiltration and osmotic shifts lead to rapid intravascular volume changes and blood pressure variability, which may alter ocular perfusion. Previous studies have demonstrated that these physiological changes can induce transient structural and vascular alterations in the retina and choroid. For example, Chen et al. reported increased macular retinal nerve fiber layer thickness together with reduced choroidal thickness shortly after hemodialysis, suggesting that rapid fluid redistribution and osmotic shifts may influence ocular tissues [ 13 ]. Consistent with these findings, several OCT and OCTA studies have reported decreases in subfoveal choroidal thickness following hemodialysis sessions. These reductions appear particularly evident in the temporal and nasal choroidal regions. A pooled self-controlled case series conducted by Su et al. confirmed that hemodialysis is associated with a moderate but consistent decrease in subfoveal choroidal thickness across multiple studies [ 14 ]. In addition to structural changes, dialysis-related circulatory stress may also affect ocular microvascular perfusion. Previous reports have described increased non-perfusion areas within the choriocapillaris following HD, while retinal vascular density parameters remain largely unchanged [ 13 , 15 , 16 ]. This pattern suggests that the choroidal circulation may be more sensitive to dialysis-induced hemodynamic stress compared with the retinal vasculature, which possesses stronger autoregulatory mechanisms. Previous literature also suggests that some macular alterations observed in dialysis patients may reflect transient physiological changes rather than permanent structural damage. Atilgan et al. reported that macular thinning detected before hemodialysis was not sustained during long-term follow-up, indicating that part of the macular signal may be related to short-term variations in intravascular volume and pressure rather than irreversible retinal damage [ 17 ]. Similarly, Mustafar et al. demonstrated that reductions in macular volume were more strongly associated with systemic comorbidities such as diabetes mellitus and ischemic heart disease than with renal dysfunction measured by eGFR, suggesting that macular alterations may reflect underlying cardiometabolic pathology rather than kidney disease alone [ 18 ]. With regard to the choroid, large-scale analyses have not consistently demonstrated progressive choroidal thinning across different stages of CKD [ 19 ]. However, structural changes in the choroid may become more apparent after the initiation of dialysis therapy. Nakano et al. reported significant alterations in choroidal architecture following the start of hemodialysis, with greater reductions in subfoveal choroidal thickness and large-vessel layer thickness observed in diabetic patients compared with non-diabetic individuals [ 20 ]. These findings suggest that diabetic patients undergoing hemodialysis may have a more vulnerable choroidal circulation, which may compromise the outer retinal layers that depend on choroidal blood supply. Such vascular alterations, together with chronic retinal hypoperfusion, may contribute to progressive visual decline, increased risk of diabetic retinopathy, and even acute vision loss in ESRD patients receiving hemodialysis [ 21 ]. Our findings partially align with the existing literature but also provide additional insights. In the present study, we compared retinal and choroidal OCT and OCTA parameters between patients undergoing hemodialysis and those receiving peritoneal dialysis. The most notable finding was the significant difference in the ΔCMT between the HD and PD groups, suggesting that hemodialysis may induce more pronounced acute alterations in macular structure. In contrast, most OCTA-derived vascular parameters—including FAZ area, FAZ perimeter, and vessel density measurements in the superficial and deep capillary plexuses—did not differ significantly between the two dialysis modalities. Similarly, changes in choroidal thickness were not statistically different between groups. The physiological differences between dialysis modalities may explain these findings. Hemodialysis is characterized by intermittent treatment sessions with relatively rapid fluid removal and hemodynamic fluctuations, whereas peritoneal dialysis provides slower and more continuous ultrafiltration. As a result, patients undergoing HD may experience more pronounced short-term intravascular volume shifts and osmotic changes, which could affect retinal structural parameters such as macular thickness. In contrast, the more gradual fluid removal observed in PD may lead to more stable hemodynamic conditions and therefore smaller acute structural changes in retinal tissues. These findings may reflect the greater hemodynamic fluctuations associated with intermittent hemodialysis compared with the more gradual fluid removal in peritoneal dialysis. Importantly, the absence of a relationship between ultrafiltration volume and ocular parameters in our analysis suggests that the observed retinal changes may be more related to rapid hemodynamic shifts rather than the total amount of fluid removed during dialysis. This study has several limitations. First, the relatively small sample size may limit the statistical power to detect subtle differences in microvascular parameters between dialysis modalities. Second, the cross-sectional design prevents evaluation of long-term retinal and choroidal alterations associated with dialysis therapy. Third, systemic dialysis-related parameters, including ultrafiltration volume and dialysis duration, were evaluated in our analysis but did not show a significant association with ocular imaging parameters. Nevertheless, other systemic factors, such as transient hemodynamic fluctuations during dialysis sessions, may still influence ocular microcirculation. In conclusion, although most OCTA-derived retinal microvascular parameters remained stable between hemodialysis and peritoneal dialysis patients, macular thickness changes differed between dialysis modalities. These findings suggest that intermittent hemodialysis may induce more pronounced short-term structural retinal changes compared with peritoneal dialysis, likely due to greater hemodynamic and osmotic stress. OCT and OCTA imaging may therefore provide valuable noninvasive insights into microvascular responses in patients with ESRD undergoing dialysis. CONCLUSION Our findings suggest that although most OCTA-derived retinal microvascular parameters remain stable between hemodialysis and peritoneal dialysis patients, macular thickness changes may differ between dialysis modalities. These findings may provide insight into the microvascular effects of dialysis modalities and contribute to the understanding of subclinical retinal alterations in systemic disease. These differences may reflect the greater hemodynamic and osmotic stress associated with intermittent hemodialysis compared with the more gradual fluid removal observed in peritoneal dialysis. OCT and OCTA imaging may therefore serve as useful noninvasive tools for evaluating microvascular responses in patients with ESRD undergoing dialysis. Declarations Author Contribution B.A.A., E.A.S and T.S conceived and designed the study. B.A.A. collected the data. B.A.A. and L.E performed the statistical analysis. B.A.A. drafted the manuscript. AA,L.E., E.A.S, and T.S contributed to data interpretation and critically revised the manuscript for important intellectual content. All authors approved the final version of the manuscript and agree to be accountable for all aspects of the work. Acknowledgement The authors would like to thank all participants who contributed to this study. Data Availability The datasets generated and/or analyzed during the current study are not publicly available due to patient privacy and institutional regulations but are available from the corresponding author on reasonable request. References Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2024 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney Int Suppl. 2024;105(4S): S117-S314. Patel PP, Egodage T. Failing kidneys: renal replacement therapies in the ICU. Trauma Surg Acute Care Open. 2024;9(Suppl 2):e001381. Goodbred AJ, Langan RC. Chronic kidney disease: prevention, diagnosis, and treatment. Am Fam Physician. 2023;108(6):554-61. Zhang Y, Yu C, Li X. Kidney aging and chronic kidney disease. Int J Mol Sci. 2024;25(12):6585. Spasiano A, Benedetti C, Gambaro G, Ferraro PM. 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BMC Ophthalmol. 2023, 23, 55. Majithia, S.; Chong, C.C.Y.; Chee, M.L.; Yu, M.; Soh, Z.D.; Thakur, S.; Lavanya, R.; Rim, T.H.; Nusinovici, S.; Koh, V.; et al. Associations between Chronic Kidney Disease and Thinning of Neuroretinal Layers in Multiethnic Asian and White Populations. Ophthalmol. Sci. 2024, 4, 100353. Choi, S.U.; Oh, J.Y.; Kim, J.T. Correlations between choroidal thickness and renal function in patients with retinal vein occlusion. Sci. Rep. 2020, 10, 16865. Farrah, T.E.; Dhillon, B.; Keane, P.A.; Webb, D.J.; Dhaun, N. The eye, the kidney, and cardiovascular disease: Old concepts, better tools, and new horizons. Kidney Int. 2020, 98, 323–342 Chen, H.; Zhang, X.; Shen, X. Ocular changes during hemodialysis in patients with end-stage renal disease. BMC Ophthalmol.2018, 18, 208. Su, Z.; Mao, Y.; Qi, Z.; Xie, M.; Liang, X.; Hu, B.; Wang, X.; Jiang, F. Impact of Hemodialysis on Subfoveal Choroidal Thickness Measured by Optical Coherence Tomography: A Systematic Review and a Pooled Analysis of Self-Controlled Case Series. Ophthalmol. Ther. 2023, 12, 2265–2280 Zegrari, S.; Mouallem, A.; Audard, V.; Jouan, N.; Grimbert, P.; Jung, C.; Sakhi, H.; Souied, E.H.; Miere, A. Optical coherence tomography angiography analysis of changes in the retina and the choroid after hemodialysis for end-stage kidney disease. Int.Ophthalmol. 2023, 43, 4473–4479. Shoshtari, F.S.; Biranvand, S.; Rezaei, L.; Salari, N.; Aghaei, N. The impact of hemodialysis on retinal and choroidal thickness in patients with chronic renal failure. Int. Ophthalmol. 2021, 41, 1763–1771. Atilgan, C.U.; Guven, D.; Akarsu, O.P.; Sakaci, T.; Sendul, S.Y.; Baydar, Y.; Atilgan, K.G.; Turker, I.C. Effects of hemodialysis on macular and retinal nerve fiber layer thicknesses in non-diabetic patients with end-stage renal failure. Saudi Med. J. 2016,37, 641–647 Mustafar, R.; Hishamuddin, K.A.M.; Mohd, R.; Kamaruzaman, L.; Halim, W.H.W.A.; Hsien, Y.M.; Sze, T.K.; Zaki, W.M.D.W.; Ali,A.; Bain, A. Retinal changes and cardiac biomarker assessment in relation to chronic kidney disease: A single centre study. BMCNephrol. 2023, 24, 338 Tang, M.; Lin, L.; Liu, S.; Li, Z.; Zeng, L.; Hao, Y. Correlation between Fundus Damage and Renal Function Deterioration in Chronic Kidney Disease Patients. Kidney Blood Press. Res. 2024, 49, 1003–1012 He, K.; Liu, S.; Shi, J.; Zhang, P.; Chen, L.; Wang, B.; Zhang, J. The effect of long-term hemodialysis on diabetic retinopathy observed by swept-source optical coherence tomography angiography. BMC Ophthalmol. 2024, 24, 334. Mullaem, G.; Rosner, M.H. Ocular Problems in the Patient with End-Stage Renal Disease. Semin. Dial. 2012, 25, 403–407. Tables Tables 1 to 5 are available in the supplementary files section Additional Declarations No competing interests reported. Supplementary Files tables.docx Cite Share Download PDF Status: Under Review Version 1 posted Reviews received at journal 28 Apr, 2026 Reviewers agreed at journal 14 Apr, 2026 Reviewers invited by journal 13 Apr, 2026 Editor assigned by journal 10 Apr, 2026 Submission checks completed at journal 10 Apr, 2026 First submitted to journal 08 Apr, 2026 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-9360672","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":625251404,"identity":"292044c4-2b64-47b3-9c65-78234841a496","order_by":0,"name":"Binhan Aslan Akbulut","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA40lEQVRIiWNgGAWjYBACA2YGNjCDj4GB8QGQ5uEjWguQZDYAaWEjqIUBoYVNAsrAD8zZeY89+LnDzp6N/eyxyq85djJsDMwPH93Ao8WymS/dsPdMcmIbT17abdltyUCHsRkb5+Bz2GEeMwneNuYENoYcs9uS25iBWnjYpAlpkfzbVm/Pxv/GrFhyWz1xWqR52w4ztknkmDF+3HaYsBbLZqAW2bbjiW0Sb4ylGbcd52FjJuAXc/4zZpJv26rt+flzDD/+3AZksDc/fIxPCwpg5gGTxCoHAcYfpKgeBaNgFIyCEQMA1oc6rlNE63EAAAAASUVORK5CYII=","orcid":"","institution":"Adana City Training and Research Hospital","correspondingAuthor":true,"prefix":"","firstName":"Binhan","middleName":"Aslan","lastName":"Akbulut","suffix":""},{"id":625251405,"identity":"bbc992a8-e192-48bc-94a7-b02cb25a3255","order_by":1,"name":"Ahmet Altıntaş","email":"","orcid":"","institution":"Osmaniye Training and Research Hospital","correspondingAuthor":false,"prefix":"","firstName":"Ahmet","middleName":"","lastName":"Altıntaş","suffix":""},{"id":625251406,"identity":"809f6946-b45a-4a2a-afd6-a560586d90b2","order_by":2,"name":"Emine Alyamaç Sukgen","email":"","orcid":"","institution":"Sukgen Clinic","correspondingAuthor":false,"prefix":"","firstName":"Emine","middleName":"Alyamaç","lastName":"Sukgen","suffix":""},{"id":625251407,"identity":"d83bc4d2-b5b3-4d1b-b97f-5a1593cfaf6e","order_by":3,"name":"Tayyibe Saler","email":"","orcid":"","institution":"Adana City Training and Research Hospital","correspondingAuthor":false,"prefix":"","firstName":"Tayyibe","middleName":"","lastName":"Saler","suffix":""},{"id":625251408,"identity":"c5de428a-b793-44be-bc90-4b29125eae1e","order_by":4,"name":"Lina Elmas","email":"","orcid":"","institution":"Çaldıran State Hospital","correspondingAuthor":false,"prefix":"","firstName":"Lina","middleName":"","lastName":"Elmas","suffix":""}],"badges":[],"createdAt":"2026-04-08 19:38:20","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9360672/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9360672/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107315582,"identity":"d52ebcce-e2e7-48b3-b106-bd910d02d230","added_by":"auto","created_at":"2026-04-20 09:43:53","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":164231,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9360672/v1/2e385810-f46a-4aff-9494-aea776cfc619.pdf"},{"id":107315482,"identity":"0b94a70d-37cd-4b05-a4b9-d5a8b7f1bb70","added_by":"auto","created_at":"2026-04-20 09:43:41","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":17247,"visible":true,"origin":"","legend":"","description":"","filename":"tables.docx","url":"https://assets-eu.researchsquare.com/files/rs-9360672/v1/35b0b4f02edf93375059f46f.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eReti̇nal and Choroi̇dal Mi̇crovascular Changes İn Hemodi̇alysi̇s and Peri̇toneal Di̇alysi̇s: A Comparati̇ve Oct and Oct-a Study\u003c/p\u003e","fulltext":[{"header":"INTRODUCTION","content":"\u003cp\u003eChronic kidney disease (CKD) is an important public health problem worldwide, associated with increasing prevalence and high morbidity and mortality. CKD is defined as kidney damage lasting at least three months or an estimated glomerular filtration rate (eGFR) below 60 mL/min/1.73 m\u0026sup2;. According to the Kidney Disease Outcomes Quality Initiative (KDOQI) classification, CKD has five stages based on eGFR, with stage 5 representing end-stage renal disease (ESRD) and an eGFR below 15 mL/min/1.73 m\u0026sup2; [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn patients with ESRD, renal replacement therapies (RRT) are required to maintain metabolic balance. The main RRT modalities include hemodialysis, peritoneal dialysis, and renal transplantation [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Peritoneal dialysis can be performed as continuous ambulatory peritoneal dialysis (CAPD) or automated peritoneal dialysis (APD), depending on the dialysis protocol.CKD is a systemic condition that affects multiple organs and systems, including the cardiovascular, endocrine, gastrointestinal, and nervous systems. Ocular involvement is also common, particularly in patients with underlying diseases such as diabetes mellitus and hypertension, which may lead to ocular complications including diabetic and hypertensive retinopathy [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eDialysis treatment induces significant systemic hemodynamic and osmotic changes, including alterations in blood pressure, plasma osmolarity, and fluid balance. These changes may influence ocular structures, particularly the retina and choroid, which are highly vascularized tissues [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Previous studies have suggested that dialysis may lead to measurable alterations in retinal thickness, choroidal thickness, and retinal microvascular circulation; however, the exact mechanisms and clinical implications remain incompletely understood [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn patients with ESRD, hemodialysis introduces unique physiological stressors that may influence ocular circulation and structure. Ultrafiltration, osmotic shifts, and fluctuations in systemic blood pressure occurring during dialysis sessions can acutely affect ocular perfusion and tissue thickness, particularly in highly vascular structures such as the choroid. Previous studies have demonstrated that hemodialysis may induce measurable changes in ocular parameters, including retinal and choroidal thickness. Recent meta-analyses have reported a modest but consistent decrease in subfoveal choroidal thickness following hemodialysis, whereas retinal thickness parameters generally show minimal acute alterations. These findings suggest that the choroidal circulation may be more sensitive to systemic hemodynamic and fluid shifts occurring during dialysis sessions [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eBeyond these acute dialysis-related changes, chronic kidney disease has also been associated with long-term structural alterations in ocular tissues. Retinal arteriolar narrowing, progressive choroidal thinning, and thinning of the retinal nerve fiber layer (RNFL) and ganglion cell\u0026ndash;inner plexiform layer (GCIPL) have been reported in patients with CKD. These structural changes appear to be closely related to systemic microvascular damage and are frequently exacerbated by comorbid conditions such as diabetes mellitus and hypertension [\u003cspan additionalcitationids=\"CR9 CR10\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eBecause the retinal and renal microvasculature share similar structural and autoregulatory characteristics, alterations detected in retinal and choroidal structures may reflect systemic microvascular dysfunction. Several studies have demonstrated associations between ocular structural parameters and markers of renal impairment, including decreased eGFR and increased albuminuria [\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. Consequently, ocular imaging techniques may provide valuable, non-invasive biomarkers for evaluating microvascular damage in CKD.\u003c/p\u003e \u003cp\u003eIn recent years, optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) have become widely used imaging modalities for the evaluation of retinal and choroidal structures. OCT allows detailed assessment of retinal thickness parameters such as central macular thickness (CMT) and choroidal thickness, while OCTA enables non-invasive visualization and quantitative evaluation of retinal microvasculature. These technologies provide important insights into microvascular alterations that may occur in systemic diseases such as CKD.\u003c/p\u003e \u003cp\u003eTherefore, the present study aimed to evaluate retinal and choroidal structural parameters using OCT and OCTA in patients undergoing hemodialysis and peritoneal dialysis, and to investigate the potential effects of dialysis-related hemodynamic changes on ocular measurements. Understanding these ocular alterations may contribute to a better characterization of systemic microvascular dysfunction in patients with chronic kidney disease and may provide useful biomarkers for monitoring disease-related vascular changes. To the best of our knowledge, limited studies are comparing ocular structural parameters between hemodialysis and peritoneal dialysis using OCT and OCTA.\u003c/p\u003e"},{"header":"METHODS","content":"\u003cp\u003eThis prospective observational study was conducted in 2021 at the Dialysis Unit of Adana City Training and Research Hospital, T\u0026uuml;rkiye. Patients undergoing hemodialysis (HD) or peritoneal dialysis (PD) who were regularly followed in the dialysis clinic were included in the study. Ophthalmologic examinations were performed at two time points according to the dialysis modality. For hemodialysis patients, ocular measurements were obtained 30 minutes before the dialysis session and 30 minutes after the completion of dialysis, both at rest. For peritoneal dialysis patients, measurements were performed 15 minutes after draining the dialysate and 2 hours after refilling the dialysate, also at rest. A total of 84 eyes from 46 patients were included in the analysis.\u003c/p\u003e \u003cp\u003ePatients with ocular conditions that could affect retinal or choroidal measurements, such as significant media opacity, previous retinal surgery, advanced glaucoma, or retinal vascular diseases, were excluded from the study. The study adhered to the principles of the Declaration of Helsinki. Ethical approval was obtained from the Adana City Training and Research Hospital Ethics Committee (Approval No: 1358), and written informed consent was obtained from all participants. All participants underwent a comprehensive ophthalmologic examination at each visit.\u003c/p\u003e \u003cp\u003eThe examination included:\u003c/p\u003e \u003cp\u003eBest-corrected visual acuity (BCVA) measurement using a Snellen chart and converted to logMAR for statistical analysis\u003c/p\u003e \u003cp\u003eSlit-lamp biomicroscopic examination\u003c/p\u003e \u003cp\u003eIntraocular pressure measurement using tonometry\u003c/p\u003e \u003cp\u003eDilated fundus examination\u003c/p\u003e \u003cp\u003eOptical coherence tomography angiography (OCTA) images were obtained using the AngioVue OCTA system (Optovue Inc., Fremont, CA, USA). Macular scans were acquired using a 3\u0026times;3 mm scanning protocol centered on the fovea.\u003c/p\u003e \u003cp\u003eThe following parameters were recorded from OCTA images: superficial capillary plexus (SCP) vessel density (whole, foveal, parafoveal), deep capillary plexus (DCP) vessel density (whole, foveal, parafoveal), foveal avascular zone (FAZ) area, FAZ perimeter,CMT\u003c/p\u003e \u003cp\u003eOnly OCTA images with a signal quality score of \u0026ge;\u0026thinsp;5 (Q5) were included in the analysis. Images with poor quality or significant motion artifacts were excluded.\u003c/p\u003e \u003cp\u003eSubfoveal choroidal thickness was measured manually on raster B-scan images obtained from the same AngioVue device (Optovue Inc., Fremont, CA, USA). Choroidal thickness was defined as the vertical distance between the outer border of the retinal pigment epithelium (RPE) and the choroid\u0026ndash;sclera interface. Each measurement was performed three times, and the mean value of these three measurements was used for statistical analysis to reduce measurement variability.\u003c/p\u003e \u003cp\u003eThe same experienced ophthalmologist performed all OCTA image acquisitions and manual measurements to ensure measurement consistency.\u003c/p\u003e \u003cp\u003eAll statistical analyses were performed using IBM SPSS Statistics software (IBM Corp., Armonk, NY, USA). The Shapiro\u0026ndash;Wilk test was used to evaluate the normality of the data distribution. All statistical analyses were performed using IBM SPSS Statistics software (IBM Corp., Armonk, NY, USA). Continuous variables were expressed as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard deviation (SD), while categorical variables were presented as frequencies and percentages. The Shapiro\u0026ndash;Wilk test was used to evaluate the normality of the data distribution. Comparisons between pre-dialysis and post-dialysis measurements were performed using the Wilcoxon signed-rank test. Differences between hemodialysis and peritoneal dialysis groups were analyzed using the Mann\u0026ndash;Whitney U test. Correlations between systemic dialysis parameters and ocular measurements were assessed using Spearman correlation analysis.\u003c/p\u003e \u003cp\u003ep-value\u0026thinsp;\u0026lt;\u0026thinsp;0.05 was considered statistically significant.\u003c/p\u003e"},{"header":"RESULTS","content":"\u003cp\u003eA total of 84 eyes from 46 patients undergoing dialysis were included in the study. Of these, 49 eyes (58.3%) belonged to patients receiving hemodialysis (HD) and 35 eyes (41.7%) belonged to patients undergoing peritoneal dialysis (PD). The mean age of the study population was 47.71\u0026thinsp;\u0026plusmn;\u0026thinsp;12.92 years. The mean age was 47.63\u0026thinsp;\u0026plusmn;\u0026thinsp;12.07 years in the HD group and 47.83\u0026thinsp;\u0026plusmn;\u0026thinsp;14.20 years in the PD group. The mean body mass index (BMI) was 25.27\u0026thinsp;\u0026plusmn;\u0026thinsp;4.16 kg/m\u0026sup2; overall, 24.85\u0026thinsp;\u0026plusmn;\u0026thinsp;4.43 kg/m\u0026sup2; in HD patients, and 25.86\u0026thinsp;\u0026plusmn;\u0026thinsp;3.74 kg/m\u0026sup2; in PD patients.\u003c/p\u003e \u003cp\u003eThe mean dialysis session duration was 4.81\u0026thinsp;\u0026plusmn;\u0026thinsp;0.99 hours. Session duration was 4.00\u0026thinsp;\u0026plusmn;\u0026thinsp;0.00 hours in the HD group and 5.94\u0026thinsp;\u0026plusmn;\u0026thinsp;0.34 hours in the PD group. The mean ultrafiltration volume was 2730.95\u0026thinsp;\u0026plusmn;\u0026thinsp;1020.83 mL, with 3065.31\u0026thinsp;\u0026plusmn;\u0026thinsp;1228.24 mL in HD patients and 2262.86\u0026thinsp;\u0026plusmn;\u0026thinsp;165.98 mL in PD patients. (Table\u0026nbsp;1 )\u003c/p\u003e \u003cp\u003eBefore dialysis, the mean CMT was 208.43\u0026thinsp;\u0026plusmn;\u0026thinsp;17.80 \u0026micro;m. The mean foveal avascular zone (FAZ) area was 0.312\u0026thinsp;\u0026plusmn;\u0026thinsp;0.121 mm\u0026sup2;, and the FAZ perimeter was 2.26\u0026thinsp;\u0026plusmn;\u0026thinsp;0.50 mm.\u003c/p\u003e \u003cp\u003eThe mean SCP vessel density was 44.94\u0026thinsp;\u0026plusmn;\u0026thinsp;4.79% in the whole image, 14.94\u0026thinsp;\u0026plusmn;\u0026thinsp;6.19% in the fovea, and 48.09\u0026thinsp;\u0026plusmn;\u0026thinsp;5.13% in the parafoveal region.\u003c/p\u003e \u003cp\u003eFor the DCP, the mean vessel density values were 50.67\u0026thinsp;\u0026plusmn;\u0026thinsp;4.79% in the whole image, 31.31\u0026thinsp;\u0026plusmn;\u0026thinsp;7.92% in the fovea, and 52.89\u0026thinsp;\u0026plusmn;\u0026thinsp;5.04% in the parafoveal region.\u003c/p\u003e \u003cp\u003eThe mean subfoveal choroidal thickness was 250.90\u0026thinsp;\u0026plusmn;\u0026thinsp;42.40 \u0026micro;m, and the mean best-corrected visual acuity (BCVA) was 0.081\u0026thinsp;\u0026plusmn;\u0026thinsp;0.114 logMAR. (Table\u0026nbsp;2)\u003c/p\u003e \u003cp\u003eAfter dialysis, the mean central macular thickness was 209.85\u0026thinsp;\u0026plusmn;\u0026thinsp;17.45 \u0026micro;m. The mean FAZ area was 0.318\u0026thinsp;\u0026plusmn;\u0026thinsp;0.128 mm\u0026sup2;, and the FAZ perimeter was 2.28\u0026thinsp;\u0026plusmn;\u0026thinsp;0.54 mm. The mean SCP vessel density was 44.71\u0026thinsp;\u0026plusmn;\u0026thinsp;5.14% in the whole image, 14.86\u0026thinsp;\u0026plusmn;\u0026thinsp;6.22% in the fovea, and 47.64\u0026thinsp;\u0026plusmn;\u0026thinsp;5.64% in the parafoveal region. The mean DCP vessel density values were 50.48\u0026thinsp;\u0026plusmn;\u0026thinsp;5.16% in the whole image, 30.89\u0026thinsp;\u0026plusmn;\u0026thinsp;7.96% in the fovea, and 52.70\u0026thinsp;\u0026plusmn;\u0026thinsp;5.19% in the parafoveal region. The mean subfoveal choroidal thickness after dialysis was 245.68\u0026thinsp;\u0026plusmn;\u0026thinsp;46.53 \u0026micro;m, and the mean BCVA was 0.075\u0026thinsp;\u0026plusmn;\u0026thinsp;0.098 logMAR. (Table\u0026nbsp;3)\u003c/p\u003e \u003cp\u003ePre- and post-dialysis measurements were compared using the Wilcoxon signed-rank test. A statistically significant decrease was observed in central macular thickness after dialysis (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Subfoveal choroidal thickness significantly decreased following dialysis (p\u0026thinsp;=\u0026thinsp;0.013). Systemic parameters also showed significant changes during dialysis. Both systolic blood pressure (p\u0026thinsp;=\u0026thinsp;0.001) and diastolic blood pressure (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001) decreased significantly after dialysis. No statistically significant changes were observed in OCTA-derived retinal microvascular parameters, including SCP vessel density, DCP vessel density, FAZ area, FAZ perimeter, and BCVA (all p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). (Table\u0026nbsp;4)\u003c/p\u003e \u003cp\u003eThe changes in ocular and systemic parameters were compared between the HD and PD groups using the Mann-Whitney U test. A statistically significant difference was observed in the change in ΔCMT between the two dialysis modalities (p\u0026thinsp;=\u0026thinsp;0.002).In addition, changes in systolic blood pressure (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001), diastolic blood pressure (p\u0026thinsp;=\u0026thinsp;0.017), and intraocular pressure (p\u0026thinsp;=\u0026thinsp;0.006) differed significantly between the groups. However, no significant differences were detected between HD and PD patients in OCTA-derived retinal microvascular parameters, including SCP vessel density, DCP vessel density, FAZ parameters, choroidal thickness, and BCVA (all p\u0026thinsp;\u0026gt;\u0026thinsp;0.05). (Table\u0026nbsp;5)\u003c/p\u003e \u003cp\u003eSpearman correlation analysis revealed a moderate negative correlation between ΔCMT and Δsystolic blood pressure (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.372, p\u0026thinsp;\u0026lt;\u0026thinsp;0.001). Additionally, dialysis session duration showed a moderate positive correlation with ΔCMT (r\u0026thinsp;=\u0026thinsp;0.320, p\u0026thinsp;=\u0026thinsp;0.003). A weak negative correlation was observed between ultrafiltration volume and ΔDCP whole vessel density (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.239, p\u0026thinsp;=\u0026thinsp;0.028). No significant correlations were found between ultrafiltration volume and other OCTA parameters (all p\u0026thinsp;\u0026gt;\u0026thinsp;0.05).\u003c/p\u003e"},{"header":"DISCUSSION","content":"\u003cp\u003eThe retinal and choroidal microvasculature are increasingly recognized as accessible indicators of systemic microvascular health. Because the retina shares anatomical and physiological characteristics with other end-organ microvascular beds, retinal imaging techniques such as optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) offer a unique opportunity to evaluate systemic vascular alterations in vivo. In patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD), systemic microvascular dysfunction, chronic inflammation, endothelial injury, and metabolic disturbances contribute to widespread vascular alterations that may also affect ocular circulation.\u003c/p\u003e \u003cp\u003eHemodialysis, while essential for removing metabolic waste products and excess fluid, exposes patients to rapid hemodynamic and osmotic fluctuations that may influence systemic and ocular circulation [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. During a dialysis session, ultrafiltration and osmotic shifts lead to rapid intravascular volume changes and blood pressure variability, which may alter ocular perfusion. Previous studies have demonstrated that these physiological changes can induce transient structural and vascular alterations in the retina and choroid. For example, Chen et al. reported increased macular retinal nerve fiber layer thickness together with reduced choroidal thickness shortly after hemodialysis, suggesting that rapid fluid redistribution and osmotic shifts may influence ocular tissues [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eConsistent with these findings, several OCT and OCTA studies have reported decreases in subfoveal choroidal thickness following hemodialysis sessions. These reductions appear particularly evident in the temporal and nasal choroidal regions. A pooled self-controlled case series conducted by Su et al. confirmed that hemodialysis is associated with a moderate but consistent decrease in subfoveal choroidal thickness across multiple studies [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. In addition to structural changes, dialysis-related circulatory stress may also affect ocular microvascular perfusion. Previous reports have described increased non-perfusion areas within the choriocapillaris following HD, while retinal vascular density parameters remain largely unchanged [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. This pattern suggests that the choroidal circulation may be more sensitive to dialysis-induced hemodynamic stress compared with the retinal vasculature, which possesses stronger autoregulatory mechanisms.\u003c/p\u003e \u003cp\u003ePrevious literature also suggests that some macular alterations observed in dialysis patients may reflect transient physiological changes rather than permanent structural damage. Atilgan et al. reported that macular thinning detected before hemodialysis was not sustained during long-term follow-up, indicating that part of the macular signal may be related to short-term variations in intravascular volume and pressure rather than irreversible retinal damage [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. Similarly, Mustafar et al. demonstrated that reductions in macular volume were more strongly associated with systemic comorbidities such as diabetes mellitus and ischemic heart disease than with renal dysfunction measured by eGFR, suggesting that macular alterations may reflect underlying cardiometabolic pathology rather than kidney disease alone [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. With regard to the choroid, large-scale analyses have not consistently demonstrated progressive choroidal thinning across different stages of CKD [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. However, structural changes in the choroid may become more apparent after the initiation of dialysis therapy. Nakano et al. reported significant alterations in choroidal architecture following the start of hemodialysis, with greater reductions in subfoveal choroidal thickness and large-vessel layer thickness observed in diabetic patients compared with non-diabetic individuals [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. These findings suggest that diabetic patients undergoing hemodialysis may have a more vulnerable choroidal circulation, which may compromise the outer retinal layers that depend on choroidal blood supply. Such vascular alterations, together with chronic retinal hypoperfusion, may contribute to progressive visual decline, increased risk of diabetic retinopathy, and even acute vision loss in ESRD patients receiving hemodialysis [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOur findings partially align with the existing literature but also provide additional insights. In the present study, we compared retinal and choroidal OCT and OCTA parameters between patients undergoing hemodialysis and those receiving peritoneal dialysis. The most notable finding was the significant difference in the ΔCMT between the HD and PD groups, suggesting that hemodialysis may induce more pronounced acute alterations in macular structure. In contrast, most OCTA-derived vascular parameters\u0026mdash;including FAZ area, FAZ perimeter, and vessel density measurements in the superficial and deep capillary plexuses\u0026mdash;did not differ significantly between the two dialysis modalities. Similarly, changes in choroidal thickness were not statistically different between groups.\u003c/p\u003e \u003cp\u003eThe physiological differences between dialysis modalities may explain these findings. Hemodialysis is characterized by intermittent treatment sessions with relatively rapid fluid removal and hemodynamic fluctuations, whereas peritoneal dialysis provides slower and more continuous ultrafiltration. As a result, patients undergoing HD may experience more pronounced short-term intravascular volume shifts and osmotic changes, which could affect retinal structural parameters such as macular thickness. In contrast, the more gradual fluid removal observed in PD may lead to more stable hemodynamic conditions and therefore smaller acute structural changes in retinal tissues.\u003c/p\u003e \u003cp\u003eThese findings may reflect the greater hemodynamic fluctuations associated with intermittent hemodialysis compared with the more gradual fluid removal in peritoneal dialysis.\u003c/p\u003e \u003cp\u003eImportantly, the absence of a relationship between ultrafiltration volume and ocular parameters in our analysis suggests that the observed retinal changes may be more related to rapid hemodynamic shifts rather than the total amount of fluid removed during dialysis.\u003c/p\u003e \u003cp\u003eThis study has several limitations. First, the relatively small sample size may limit the statistical power to detect subtle differences in microvascular parameters between dialysis modalities. Second, the cross-sectional design prevents evaluation of long-term retinal and choroidal alterations associated with dialysis therapy. Third, systemic dialysis-related parameters, including ultrafiltration volume and dialysis duration, were evaluated in our analysis but did not show a significant association with ocular imaging parameters. Nevertheless, other systemic factors, such as transient hemodynamic fluctuations during dialysis sessions, may still influence ocular microcirculation.\u003c/p\u003e \u003cp\u003eIn conclusion, although most OCTA-derived retinal microvascular parameters remained stable between hemodialysis and peritoneal dialysis patients, macular thickness changes differed between dialysis modalities. These findings suggest that intermittent hemodialysis may induce more pronounced short-term structural retinal changes compared with peritoneal dialysis, likely due to greater hemodynamic and osmotic stress. OCT and OCTA imaging may therefore provide valuable noninvasive insights into microvascular responses in patients with ESRD undergoing dialysis.\u003c/p\u003e"},{"header":"CONCLUSION","content":"\u003cp\u003eOur findings suggest that although most OCTA-derived retinal microvascular parameters remain stable between hemodialysis and peritoneal dialysis patients, macular thickness changes may differ between dialysis modalities. These findings may provide insight into the microvascular effects of dialysis modalities and contribute to the understanding of subclinical retinal alterations in systemic disease. These differences may reflect the greater hemodynamic and osmotic stress associated with intermittent hemodialysis compared with the more gradual fluid removal observed in peritoneal dialysis. OCT and OCTA imaging may therefore serve as useful noninvasive tools for evaluating microvascular responses in patients with ESRD undergoing dialysis.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eB.A.A., E.A.S and T.S conceived and designed the study. B.A.A. collected the data. B.A.A. and L.E performed the statistical analysis. B.A.A. drafted the manuscript. AA,L.E., E.A.S, and T.S contributed to data interpretation and critically revised the manuscript for important intellectual content. All authors approved the final version of the manuscript and agree to be accountable for all aspects of the work.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eThe authors would like to thank all participants who contributed to this study.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe datasets generated and/or analyzed during the current study are not publicly available due to patient privacy and institutional regulations but are available from the corresponding author on reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eKidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2024 clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney Int Suppl. 2024;105(4S): S117-S314. \u003c/li\u003e\n\u003cli\u003ePatel PP, Egodage T. Failing kidneys: renal replacement therapies in the ICU. Trauma Surg Acute Care Open. 2024;9(Suppl 2):e001381. \u003c/li\u003e\n\u003cli\u003eGoodbred AJ, Langan RC. Chronic kidney disease: prevention, diagnosis, and treatment. Am Fam Physician. 2023;108(6):554-61. \u003c/li\u003e\n\u003cli\u003eZhang Y, Yu C, Li X. Kidney aging and chronic kidney disease. Int J Mol Sci. 2024;25(12):6585. \u003c/li\u003e\n\u003cli\u003eSpasiano A, Benedetti C, Gambaro G, Ferraro PM. Predictive models in chronic kidney disease: essential tools in clinical practice. Curr Opin Nephrol Hypertens. 2024;33(2):238-46. \u003c/li\u003e\n\u003cli\u003eLevin A, Ahmed SB, Carrero JJ, et al. Executive summary of the KDIGO 2024 clinical practice guideline for the evaluation and management of chronic kidney disease: known knowns and unknowns. Kıdney Int. 2024;105(4):684-701 \u003c/li\u003e\n\u003cli\u003eFekrazad, S.; Hassanzadeh, G.; Mousavi, A.; Shojaei, S.; Salehi, M.A.; Najimi, K.; Chhablani, J.; Arevalo, J.F. Optical Coherence Tomography Measurements Alteration in Patients with End-Stage Renal Disease after Hemodialysis. Ophthalmic Res. 2025, 68, 503\u0026ndash;520. \u003c/li\u003e\n\u003cli\u003eBineshfar, N.; Farjam, M.; Sharafi, F.; Changizi, F. Association of chronic kidney disease and retinal changes measured by optical coherence tomography: A systematic review and meta-analysis. Investig. Ophthalmol. Vis. Sci. 2024, 65, 5536.\u003c/li\u003e\n\u003cli\u003eBasiony, A.I.; Atta, S.N.; Dewidar, N.M.; Zaky, A.G. Association of chorioretinal thickness with chronic kidney disease. BMC Ophthalmol. 2023, 23, 55.\u003c/li\u003e\n\u003cli\u003eMajithia, S.; Chong, C.C.Y.; Chee, M.L.; Yu, M.; Soh, Z.D.; Thakur, S.; Lavanya, R.; Rim, T.H.; Nusinovici, S.; Koh, V.; et al. Associations between Chronic Kidney Disease and Thinning of Neuroretinal Layers in Multiethnic Asian and White Populations. Ophthalmol. Sci. 2024, 4, 100353.\u003c/li\u003e\n\u003cli\u003eChoi, S.U.; Oh, J.Y.; Kim, J.T. Correlations between choroidal thickness and renal function in patients with retinal vein occlusion. Sci. Rep. 2020, 10, 16865.\u003c/li\u003e\n\u003cli\u003eFarrah, T.E.; Dhillon, B.; Keane, P.A.; Webb, D.J.; Dhaun, N. The eye, the kidney, and cardiovascular disease: Old concepts, better tools, and new horizons. Kidney Int. 2020, 98, 323\u0026ndash;342\u003c/li\u003e\n\u003cli\u003eChen, H.; Zhang, X.; Shen, X. Ocular changes during hemodialysis in patients with end-stage renal disease. BMC Ophthalmol.2018, 18, 208.\u003c/li\u003e\n\u003cli\u003eSu, Z.; Mao, Y.; Qi, Z.; Xie, M.; Liang, X.; Hu, B.; Wang, X.; Jiang, F. Impact of Hemodialysis on Subfoveal Choroidal Thickness Measured by Optical Coherence Tomography: A Systematic Review and a Pooled Analysis of Self-Controlled Case Series. Ophthalmol. Ther. 2023, 12, 2265\u0026ndash;2280\u003c/li\u003e\n\u003cli\u003eZegrari, S.; Mouallem, A.; Audard, V.; Jouan, N.; Grimbert, P.; Jung, C.; Sakhi, H.; Souied, E.H.; Miere, A. Optical coherence tomography angiography analysis of changes in the retina and the choroid after hemodialysis for end-stage kidney disease. Int.Ophthalmol. 2023, 43, 4473\u0026ndash;4479.\u003c/li\u003e\n\u003cli\u003eShoshtari, F.S.; Biranvand, S.; Rezaei, L.; Salari, N.; Aghaei, N. The impact of hemodialysis on retinal and choroidal thickness in patients with chronic renal failure. Int. Ophthalmol. 2021, 41, 1763\u0026ndash;1771.\u003c/li\u003e\n\u003cli\u003eAtilgan, C.U.; Guven, D.; Akarsu, O.P.; Sakaci, T.; Sendul, S.Y.; Baydar, Y.; Atilgan, K.G.; Turker, I.C. Effects of hemodialysis on macular and retinal nerve fiber layer thicknesses in non-diabetic patients with end-stage renal failure. Saudi Med. J. 2016,37, 641\u0026ndash;647\u003c/li\u003e\n\u003cli\u003eMustafar, R.; Hishamuddin, K.A.M.; Mohd, R.; Kamaruzaman, L.; Halim, W.H.W.A.; Hsien, Y.M.; Sze, T.K.; Zaki, W.M.D.W.; Ali,A.; Bain, A. Retinal changes and cardiac biomarker assessment in relation to chronic kidney disease: A single centre study. BMCNephrol. 2023, 24, 338\u003c/li\u003e\n\u003cli\u003eTang, M.; Lin, L.; Liu, S.; Li, Z.; Zeng, L.; Hao, Y. Correlation between Fundus Damage and Renal Function Deterioration in Chronic Kidney Disease Patients. Kidney Blood Press. Res. 2024, 49, 1003\u0026ndash;1012\u003c/li\u003e\n\u003cli\u003eHe, K.; Liu, S.; Shi, J.; Zhang, P.; Chen, L.; Wang, B.; Zhang, J. The effect of long-term hemodialysis on diabetic retinopathy observed by swept-source optical coherence tomography angiography. BMC Ophthalmol. 2024, 24, 334.\u003c/li\u003e\n\u003cli\u003eMullaem, G.; Rosner, M.H. Ocular Problems in the Patient with End-Stage Renal Disease. Semin. Dial. 2012, 25, 403\u0026ndash;407.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 5 are available in the supplementary files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"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":"international-ophthalmology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"inte","sideBox":"Learn more about [International Ophthalmology](https://www.springer.com/journal/10792)","snPcode":"10792","submissionUrl":"https://submission.nature.com/new-submission/10792/3","title":"International Ophthalmology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-9360672/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9360672/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003ePurpose: \u003c/strong\u003eThis study aimed to evaluate the retinal and choroidal structural parameters using optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) in patients undergoing hemodialysis (HD) and peritoneal dialysis (PD). Furthermore, it examined the impact of hemodynamic alterations associated with dialysis on ocular metrics. \u003cstrong\u003eMethods:\u003c/strong\u003e This prospective observational study encompassed 84 eyes from 46 patients undergoing either HD or PD. Ocular measures were conducted at two intervals based on the dialysis modality. Measurements for HD patients were taken prior to and following dialysis; for PD patients, measurements were performed post-dialysate drainage and subsequent to refilling. Comprehensive ophthalmologic assessments and OCT/OCTA imaging were performed.Statistical analyses were used to compare pre- and post-dialysis values and to evaluate differences between groups.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e Central macular thickness (CMT) and subfoveal choroidal thickness significantly decreased after dialysis. Systolic and diastolic blood pressures also showed significant reductions. No significant changes were noted in OCTA-derived retinal microvascular metrics, including vessel density and FAZ values. A significant difference in ΔCMT was observed between the HD and PD groups. Correlation analysis indicated a moderate negative association between ΔCMT and alterations in systolic blood pressure, alongside a moderate positive correlation with the duration of dialysis.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusion:\u003c/strong\u003e While most retinal microvascular parameters remained stable, changes in macular thickness differed between the dialysis modalities. These findings indicate that hemodialysis may elicit more significant short-term structural alterations in the retina than peritoneal dialysis, possibly owing to increased hemodynamic variability.OCT and OCTA could be useful, non-invasive tools for assessing small blood vessel changes in people with end-stage renal disease who are on dialysis. Key Words:Hemodialysis,Peritoneal Dialysis,OCT-A,OCT,Coroidal Thickness\u003c/p\u003e","manuscriptTitle":"Reti̇nal and Choroi̇dal Mi̇crovascular Changes İn Hemodi̇alysi̇s and Peri̇toneal Di̇alysi̇s: A Comparati̇ve Oct and Oct-a Study","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-20 09:42:46","doi":"10.21203/rs.3.rs-9360672/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2026-04-28T07:41:43+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"152721003707607147348333409511976923375","date":"2026-04-14T22:15:04+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-13T04:04:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-04-10T07:39:36+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-04-10T07:39:21+00:00","index":"","fulltext":""},{"type":"submitted","content":"International Ophthalmology","date":"2026-04-08T19:34:06+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"international-ophthalmology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"inte","sideBox":"Learn more about [International Ophthalmology](https://www.springer.com/journal/10792)","snPcode":"10792","submissionUrl":"https://submission.nature.com/new-submission/10792/3","title":"International Ophthalmology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"37af19f0-4e91-43e2-af3c-1e83a162fbb3","owner":[],"postedDate":"April 20th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-04-20T09:42:46+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-20 09:42:46","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9360672","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9360672","identity":"rs-9360672","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}