Changes in retina and choroid after haemodialysis assessed using optical coherence tomography angiography

Linear and non-linear association of chronic kidney disease with retina and choroid vessel density in diabetes: a prospective study

PURPOSE

To investigate the association of retinal and choroidal vessel density with renal function using optical coherence tomographic angiography (OCTA).

METHOD

The present study prospectively recruited consecutive diabetes patients admitted to Beijing Liangxiang Hospital from October 2023 to March 2024. All participants underwent comprehensive ophthalmologic examinations and laboratory analysis at the first visit. Quantitative parameters of OCTA scans included retinal superficial vascular complex (SVC) and deep vascular complex (DVC) vessel densities, and choriocapillaris flow deficits (CCFD%).

RESULTS

A total of 85 patients were included in the present study. After adjusting for severity of diabetic retinopathy and other confounding factors, every 1 % increased SVC within in ETDRS grid was associated with reduced incidence of CKD (OR=0.86 95 %CI:[0.73-1.01]), decreased urine albumin-to-creatinine ratio (ACR, coefficient=-0.65, 95 %CI:[-1.22, -0.08]), and increased eGFR (coefficient=1.55, 95 %CI:[0.14, 2.96]). Every 1 % increased CCFD% was significantly associated with increased incidence of CKD (OR=1.72, 95 %CI:[1.14-2.58]) and decrease eGFR (coefficient=-6.47, 95 %CI:[-9.68, -3.26]). Non-linear regression revealed that SVC vessel density was associated with eGFR among patients with advanced retinal microvasculature damage.

CONCLUSIONS

Retina and choroid blood flow were associated with the onset and severity of CKD. Decreased SVC and decreased CCFD% can be used for non-invasively screening CKD in diabetes patients.

The effects of hemodialysis on the eye

The purpose of this study was to examine the effects of hemodialysis on the eye and its long-term consequences. Hemodialysis is a process that purifies the blood and maintains the balance of water, solutes, acid-base, and electrolytes. The eye, being primarily composed of fluid, has been speculated to be affected by this technique. To analyze these effects, a literature review was conducted, focusing on the anatomical structures, functions, and changes in the eye following hemodialysis. The search for relevant articles was carried out on PubMed, including studies published in English between 2000 and 2023. The results of the review showed that certain observations such as visual acuity, refraction, intraocular pressure, biometric parameters, and retinal nerve fiber layer did not show significant timing-related impacts, or there were conflicting findings. However, a connection was established between hemodialysis sessions and visual fields, parameters of visual-evoked potential, intraocular pressure in glaucoma, tear break-up time, Schirmer's test values, choroidal thickness, flow velocities of vessels, and ocular perfusion pressure values. In conclusion, it was determined that hemodialysis sessions can cause fluctuations that may complicate the assessment of eye health. To obtain a more accurate baseline evaluation, it is recommended to schedule ophthalmological examinations, a few hours after the hemodialysis session. Additionally, it is important to provide appropriate management for dry eyes and ocular hypertension, particularly during hemodialysis sessions. Coordination of these examinations with the timing of renal replacement therapy is advised to ensure optimal patient care.

The Association of Urinary Sodium Excretion with Glaucoma and Related Traits in a Large United Kingdom Population

PURPOSE

Excessive dietary sodium intake has known adverse effects on intravascular fluid volume and systemic blood pressure, which may influence intraocular pressure (IOP) and glaucoma risk. This study aimed to assess the association of urinary sodium excretion, a biomarker of dietary intake, with glaucoma and related traits, and determine whether this relationship is modified by genetic susceptibility to disease.

DESIGN

Cross-sectional observational and gene-environment interaction analyses in the population-based UK Biobank study.

PARTICIPANTS

Up to 103 634 individuals (mean age: 57 years; 51% women) with complete urinary, ocular, and covariable data.

METHODS

Urine sodium:creatinine ratio (UNa:Cr; mmol:mmol) was calculated from a midstream urine sample. Ocular parameters were measured as part of a comprehensive eye examination, and glaucoma case ascertainment was through a combination of self-report and linked national hospital records. Genetic susceptibility to glaucoma was calculated based on a glaucoma polygenic risk score comprising 2673 common genetic variants. Multivariable linear and logistic regression, adjusted for key sociodemographic, medical, anthropometric, and lifestyle factors, were used to model associations and gene-environment interactions.

MAIN OUTCOME MEASURES

Corneal-compensated IOP, OCT derived macular retinal nerve fiber layer and ganglion cell-inner plexiform layer (GCIPL) thickness, and prevalent glaucoma.

RESULTS

In maximally adjusted regression models, a 1 standard deviation increase in UNa:Cr was associated with higher IOP (0.14 mmHg; 95% confidence interval [CI], 0.12-0.17; P < 0.001) and greater prevalence of glaucoma (odds ratio, 1.11; 95% CI, 1.07-1.14; P < 0.001) but not macular retinal nerve fiber layer or ganglion cell-inner plexiform layer thickness. Compared with those with UNa:Cr in the lowest quintile, those in the highest quintile had significantly higher IOP (0.45 mmHg; 95% CI, 0.36-0.53, P < 0.001) and prevalence of glaucoma (odds ratio, 1.30; 95% CI, 1.17-1.45; P < 0.001). Stronger associations with glaucoma (P interaction = 0.001) were noted in participants with a higher glaucoma polygenic risk score.

CONCLUSIONS

Urinary sodium excretion, a biomarker of dietary intake, may represent an important modifiable risk factor for glaucoma, especially in individuals at high underlying genetic risk. These findings warrant further investigation because they may have important clinical and public health implications.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

The Impact of a Single Haemodialysis Session on the Retinal Thickness and Optic Nerve Morphology

BACKGROUND

The aim of the study was to assess the influence of a single haemodialysis (HD) session on the retinal and optic nerve morphology in end-stage kidney disease (ESKD) patients.

METHODS

It is a prospective study including only the right eye of 35 chronic kidney disease (CKD) patients subjected to HD. Each patient underwent a full eye examination 30 min before HD (8 a.m.) and 15 min after HD. Optical coherence tomography (OCT) was used to assess the peripapillary retinal nerve fibre layer (pRNFL) thickness, macular nerve fibre layer (mRNFL) thickness, ganglion cell layer with inner plexiform layer thickness (GCL+), GCL++ (mRNFL and GCL+) thickness, total retinal thickness (RT) and total macular volume (TMV). The correlation was tested between such systemic parameters changes as systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), body weight, plasma osmolarity and ocular perfusion pressure (OPP) and ultrafiltration volume with total RT and pRNFL thickness changes during HD.

RESULTS

In the results of a single HD session, we could observe a statistically significant increase in the total RT thickness (pre-HD 270.4 ± 19.94 μm, post-HD 272.14 ± 20.11 μm; p = 0.0014), TMV (pre-HD 7.48 ± 0.53 mm3, post-HD 7.52 ± 0.55 mm3; p = 0.0006), total pRNFL thickness (pre-HD 97.46 ± 15.71 μm, post-HD 100.23 ± 14.7 μm; p = 0.0039), total GCL+ thickness (pre-HD 70.11 ± 9.24 μm, post-HD 70.6 ± 9.7 μm; p = 0.0044), and GCL++ thickness (pre-HD 97.46 ± 12.56 μm, post-HD 97.9 ± 12.94 μm; p = 0.0081). We observed a significant correlation between the change in total RT and DBP change, as well as between body weight change and the change in total pRNFL thickness. There was also a correlation between total pRNFL thickness change and the presence of diabetes mellitus.

CONCLUSION

Even a single HD session affects the retinal and pRNFL thickness, which should be taken into account when interpreting the OCT results in patients subjected to HD. The impact of changes after a single HD session on selected parameters requires further assessment in subsequent studies, including long-term observation.

The Haemodialysis Session Effect on the Choroidal Thickness and Retinal and Choroidal Microcirculation-A Literature Review

Haemodialysis (HD) is currently the most commonly used method of renal replacement therapy. The process of dialysis involves numerous changes that affect many systems, including the eye. The changes occurring in the course of HD may affect the ocular parameters, such as intraocular pressure, central corneal thickness, retinal thickness, retinal nerve fibre layer thickness, and choroidal thickness (CT). The choroid, being one of the most vascularized tissues, is characterized by the highest ratio of blood flow to tissue volume in the entire body, may be particularly susceptible to changes occurring during HD, and at the same time reflect the microcirculatory status and its response to HD. Patients with end-stage renal disease subjected to dialysis are highly susceptible to systemic microvascular dysfunction. Moreover, it is considered that the process of HD itself contributes to vascular dysfunction. Nowadays, thanks to the development of imaging techniques, the widely available optical coherence tomography (OCT) tests allow for the assessment of CT, while OCT-angiography allows for a quick, non-invasive, and repeatable assessment of the condition of retinal and choroidal microcirculation, which significantly expands our knowledge regarding the reaction of ocular microcirculation due to HD. The assessment of both retinal and choroidal circulation is even more attractive because retinal circulation is autoregulated, while choroidal circulation is mainly controlled by extrinsic autonomic innervation. Thus, assessment of the choroidal response to an HD session may provide the possibility to indirectly evaluate the functions of the autonomic system in patients subjected to HD. At a time when the importance of microcirculation in systemic and renal diseases is becoming increasingly evident, the assessment of ocular microcirculation appears to be a potential biomarker for assessing the condition of systemic microcirculation. In this work, we present a review of the literature on the effect of the HD session on CT and the retinal and choroidal microcirculation.

Impact of Hemodialysis on Subfoveal Choroidal Thickness Measured by Optical Coherence Tomography: A Systematic Review and a Pooled Analysis of Self-Controlled Case Series

INTRODUCTION

Hemodialysis (HD) has various effects on the body, including optimizing body fluid composition and volume, which may have an impact on subfoveal choroidal thickness (SCT) in individuals with end-stage kidney disease (ESKD). However, previous studies have produced conflicting results regarding the effect of HD on SCT in patients with ESKD. Therefore, we conducted a meta-analysis to investigate the influence of HD on SCT.

METHODS

A comprehensive search of relevant studies and bibliographies was conducted using Embase, PubMed, and Web of Science databases up to September 2022. Weighted mean difference (WMD) and 95% confidence interval (CI) were used to summarize the SCT change. Heterogeneity and publication bias were assessed, and a random-effects model was employed for the meta-analysis. Subgroup analyses were also performed to evaluate the influence of factors such as diabetes mellitus (DM), the severity of diabetic retinopathy (DR), diurnal variation adjustment, optical coherence tomography (OCT) types, and OCT scan modes.

RESULTS

A total of 15 studies involving 1010 eyes were eligible for this meta-analysis, including 552 diabetic eyes, 230 non-diabetic eyes, and the remaining 228 eyes were uncategorized. The meta-analysis revealed a significant reduction in SCT after HD (WMD = -13.66 μm; 95% CI -24.29 to -3.03 μm; z = -5.115, P < 0.0001). Subgroup analysis indicated a significant difference between the DM and non-DM groups (WMD = -24.10 μm vs. -15.37 μm, 95% CI -27.39 to -20.80 μm vs. -19.07 to -11.66 μm; P = 0.001). Additionally, the group with proliferative diabetic retinopathy (PDR) exhibited a more pronounced reduction in SCT (WMD =  -28.66 μm; 95% CI -37.10 to -20.23; z = -6.660, P < 0.0001). Adjusting for diurnal variation, different types or scan modes of OCT did not significantly affect the results.

CONCLUSION

HD leads to a significant decrease in SCT among patients with ESKD, especially in patients with DM with PDR.

Macular microvasculature in patients with thyroid-associated orbitopathy: a cross-sectional study

PURPOSE

The aim of this study was to evaluate macular blood flow in patients with thyroid-associated orbitopathy (TAO) as compared to healthy subjects. The inflammatory nature of the disease, as well as the vascular congestion caused by the increase in the volume of orbital soft tissue and extraocular muscles, rationalize the assessment of retinal blood flow changes in these patients.

METHODS

This is a cross-sectional study with the convenience sampling method. Macular flow density was assessed using optical coherence tomography angiography (OCTA) and compared between patients with TAO and healthy individuals. We also compared macular flow density in two subgroups of patients based on clinical activity score (CAS).

RESULTS

Eighty-five cases, including 30 healthy individuals and 55 patients with TAO, participated. The foveal avascular zone (FAZ) area was significantly larger in the patient group than in the control. Patients with active TAO with CAS 3 or more had significantly larger FAZ areas than those with CAS less than 3 (p = 0.04).

CONCLUSION

We showed that the FAZ area is larger in active TAO patients and can be considered a possible candidate feature for monitoring disease activity and thyroid-associated vasculopathy.

Evaluation of Ocular Perfusion in Patients with End-Stage Renal Disease Receiving Hemodialysis Using Optical Coherence Tomography Angiography

Hemodialysis (HD) is known to affect ocular blood flow. This case-control study aims to evaluate macular and peripapillary vasculature in patients with end-stage renal disease (ESRD) receiving HD in comparison to matched controls. A total of 24 eyes of 24 ESRD patients receiving HD and 24 eyes of 24 healthy, age- and gender-matched control subjects were prospectively included in this study. Optical coherence tomography angiography was used to image the superficial (SCP), deep (DCP), and choriocapillary (CC) macular vascular plexus, as well as the radial peripapillary capillaries (RPC) of the optic disc. In addition, retinal thickness (RT) and retinal volume (RV) were compared between both groups. Flow density (FD) values of each retinal layer and data of parameters related to the foveal avascular zone (FAZ), as well as RT and RV, were analyzed using Mann-Whitney U tests. There was no significant difference in FAZ parameters between the two groups. Whole en face FD of the SCP and CC was noticeably reduced in the HD group in comparison to the control group. FD was negatively correlated with the duration of HD treatment. RT and RV were significantly smaller in the study group than in controls. Retinal microcirculation appears altered in patients with ESRD undergoing HD. Concurrently, the DCP appears more resilient towards hemodynamic changes in comparison to the other microvascular retinal layers. OCTA is a useful, non-invasive tool to investigate retinal microcirculation in ESRD patients.

Acquisition of optical coherence tomography angiography metrics during hemodialysis procedures: A pilot study

BACKGROUND AND AIMS

The observation of optical microcirculation gives us an extraordinary way to directly assess in vivo the responses of human circulation to stress stimuli. We run a pilot study to analyze optical coherence tomography angiography (OCT-A) metrics at determined time-points during a hemodialysis (HD) session to understand how these metrics gradually change and to evaluate possible correlations with patients' characteristics.

METHODS

After the eligibility screening, 15 patients (23 eyes) were included in the study. OCT-A parameters were collected at established time-points: Before treatment (t0), at first hour (t1), at second hour (t2), at third hour (t3), and finally at the end of HD treatment (t4). Patients were finally shared in hypotensive group if they occurred in a hypotensive episode during subsequent month methods or no hypotensive group. The instrument software automatically segmented OCT-A scans into four en-face slabs: The superficial capillary plexus (SCP), the deep capillary plexus (DCP), the outer retinal plexus and the choriocapillaris plexus. In this study we focus on SCP, DCP plexuses.

RESULTS

Overall, the majority of ophthalmic parameters remained unaffected and comparable at dialysis end; a significant reduction being observed at the end vs. starting of HD only for deep capillary plexus (DCP: Whole, fovea, and parafovea) and for central choroid thickness (CCT) (p < 0.05). An overall trend during the session showed in general a decrease with a significance in particular for DCP (whole, fovea, and parafovea) and for CCT (P = 0.006). In the hypotension group, Superficial capillary plexus (SCP: Fovea and parafovea) significantly increased comparing post vs. pre-dialysis values while CCT significantly decreased. Analyzing the trend during treatment only CCT maintained a significant trend (p for trend = 0.002). In the no-hypotension group, neither pre- vs. post-analysis and trend analysis showed a statistical significance.

CONCLUSION

Main achievement of our study was to measure, for the first time in literature, single parameters at different time-points of a HD session. As a result of this process we did not notice a brusque decreasing or increasing of OCT-A metrics but we can characterize the different effect of HD on the two distinct areas distinguishing ocular vessels: Retinal and choroidal circulation. As interesting sub-analysis, Hypotensive group showed for CCT a decreasing trend with a difference statistically significant respect to the group with no-hypotension maintaining a constant trend. In our opinion, these results suggest the role of autonomic system on vessel control in patients affected by uremia.

Retinal Degeneration: A Window to Understand the Origin and Progression of Parkinson’s Disease?

Parkinson’s disease (PD), the second most prevalent neurodegenerative disorder, manifests with motor and non-motor symptoms associated with two main pathological hallmarks, including the deterioration of dopaminergic cells and aggregation of alpha-synuclein. Yet, PD is a neurodegenerative process whose origin is uncertain and progression difficult to monitor and predict. Currently, a possibility is that PD may be secondary to long lasting peripheral affectations. In this regard, it has been shown that retinal degeneration is present in PD patients. Although it is unknown if retinal degeneration precedes PD motor symptoms, the possibility exists since degeneration of peripheral organs (e.g., olfaction, gut) have already been proven to antedate PD motor symptoms. In this paper, we explore this possibility by introducing the anatomical and functional relationship of retina and brain and providing an overview of the physiopathological changes of retinal structure and visual function in PD. On the basis of the current status of visual deficits in individuals with PD, we discuss the modalities and pathological mechanism of visual function or morphological changes in the retina and focus on the correlation between visual impairment and some representative structural features with clinical significance. To consider retinal degeneration as a contributor to PD origin and progress is important because PD evolution may be monitored and predicted by retinal studies through state-of-the-art techniques of the retina. It is significant to integrally understand the role of retinal morphological and functional changes in the neurodegenerative process for the diagnosis and therapeutic strategies of PD.

Optical coherence tomography angiography changes in cardiovascular systemic diseases and risk factors: A Review

Cardiovascular (CV) disease (CVD) is the main cause of death around the world, and assessing a patient's CV risk factors (CVRF) can play a major role in its prevention. Since it has been shown that retinal vascular alterations may reflect several systemic processes such as CVRF, we conducted a systematic review in order to summarize which ocular microvasculature changes can be found using Optical Coherence Tomography Angiography (OCTA) in patients without ocular diseases and with systemic pathologies/conditions that affect the CV system when compared to healthy subjects. We searched on online databases, namely PubMed, Scopus, Cochrane and Web of Science, and obtained additional studies through citation tracking. Case reports and review articles were excluded. A total of 47 articles were included in our review. We describe that patients with hypertension, diabetes mellitus, kidney disease, preeclampsia, coronary artery disease, carotid artery stenosis and obstructive sleep apnoea syndrome have, in general, lower retinal and choroidal Vessel Density (VD) and Length (VL), as well as an increased foveal avascular zone area and perimeter. Additionally, several characteristics and/or conditions in healthy subjects, such as smoking status, hyper or hypoxia conditions, race, among others, are also related to ocular vascular changes and should be accounted for. We concluded that OCTA could be a useful tool to assess a patient's CV risk profile in a non-invasive way, possibly integrating the diagnostic and prognostic algorithms of the most prevalent CV diseases in the future.

[Structural and microvascular changes in the retina and choroid in patients with chronic kidney disease]

PURPOSE

To study the main structural and microvascular changes in the retina and choroid in patients with diabetic retinopathy (DR) and chronic kidney disease (CKD), and their relationship with impaired renal function.

MATERIAL AND METHODS

The study included 158 patients (304 eyes). The 1^st group consisted of 50 patients with CKD (97 eyes); group 2 - 65 patients with DR (119 eyes), group 3 - 43 patients with CKD and DR (86 eyes). All study patients underwent complete ophthalmological examination, including optical coherence tomography (OCT) and OCT angiography (OCTA) of the macular region.

RESULTS

The analysis of structural parameters in groups of patients showed a decrease in the thickness of the ganglion cell layer and the inner plexiform layer of the retina in patients with DR (70.85±14.49 μm), with the lowest value in the CKD+DR group (65.84±15.34 μm) in comparison with the CKD group (75.64±10.32 μm). In the groups of patients with CKD, the thickness of the choroid (207.3±40.36 μm) was significantly reduced in comparison with the group of patients with DR (258.8±26.63 μm) and correlated with the stage of the disease. Patients in the CKD+DR group had the lowest perfusion and vascular density in the macular region (31.23±10.91% and 13.15±2.73 mm), an increase in the area and perimeter of the foveal avascular zone (0.55±0.26 mm², 3.30±0.84 mm). Pronounced correlations of decrease in choroidal thickness, vascular density, and perfusion volume with low glomerular filtration rate and CKD stage, as well as urea and creatinine levels were determined. An increase in the area of the foveal avascular zone correlated with lower retinal capillary density, decreased perfusion volume, and the stage of both DR and CKD.

CONCLUSION

Structural and hemodynamic disorders of the retina and choroid can be recognized as significant biomarkers for non-invasive diagnosis of microvascular complications of diabetes mellitus and impaired renal function.

Ocular parameters alterations after hemodialysis in patients with chronic kidney diseases

PURPOSE

To evaluate the effects of hemodialysis (HD) on visual acuity (VA), central corneal thickness (CCT), intraocular pressure (IOP), and macular thickness (MT) in chronic kidney disease (CKD) patients and also to investigate the relationship between the ocular parameters and blood biochemical parameters such as serum albumin, creatinine, sodium, and urea levels.

METHODS

A prospective cohort study including a total of 24 CKD patients of both genders (above 18 years old) undergoing HD in XXX was conducted. The participants were divided into three sub-groups based on the primary cause of renal failure, group 1: Hypertensive kidney disease, group 2: Diabetic kidney disease, group 3: Other causes. All subjects underwent full ophthalmological examinations including measurement of VA using LogMAR, IOP, CCT, and CMT. Comparisons between different ocular parameters during pre- and post-HD sessions were done using the paired t-test. The relationship between changes in ophthalmologic and blood biochemical parameters was calculated using Pearson correlation coefficient.

RESULTS

HD did not significantly alter any ocular parameter within and between CKD groups. Spherical equivalent changes were found to be significantly correlated with serum K (r = -0.315; P = 0.038), and IOP results were positively correlated with serum creatinine (r = 0.330; P = 0.029) and negatively correlated with hemoglobin (r = -0.349; P = 0.020). Bodyweight alterations were significantly correlated with CCT (r = -0.03; P = 0.0001). However, no correlation between ocular parameters and duration of HD was detected.

CONCLUSION

Following a single HD session, ocular parameters did not alter significantly.

Effect of Hemodialysis on Peripapillary Choroidal Thickness Measured by Swept-Source Optical Coherence Tomography

PURPOSE

The aim was to investigate the effects of hemodialysis (HD) on peripapillary choroidal thickness (PCT) by swept-source optical coherence tomography and on other ophthalmologic parameters in patients with end-stage kidney disease.

MATERIALS AND METHODS

This was a prospective observational study. The authors evaluated 29 patients who underwent HD for end-stage kidney disease. Detailed ophthalmologic examinations and swept-source optical coherence tomography were performed immediately before and after HD. PCT was measured using the modification tool in the built-in OCT image viewer program. Changes in PCT before and after HD were statistically analyzed.

RESULTS

The average PCT significantly decreased from 127.3±49.2 μm before HD to 117.1±50.9 μm after HD (P<0.001). A significant correlation was found between changes in PCT and macular choroidal thickness (ρ=0.547, P=0.002). Changes in mean ocular perfusion pressure did not significantly correlate with changes in PCT (ρ=-0.049, P=0.803).

CONCLUSIONS

PCT significantly decreased after HD. HD could influence the optic nerve head and its surrounding structures.

OCT angiography metrics predict intradialytic hypotension episodes in chronic hemodialysis patients: a pilot, prospective study

In chronic hemodialysis (HD) patients, intradialytic hypotension (IDH) is a complication that increases mortality risk. We run a pilot study to analyzing possible relationships between optical coherence tomography angiography (OCT-A) metrics and IDH with the aim of evaluating if OCT-A could represent a useful tool to stratify the hypotensive risk in dialysis patients. A total of 35 eyes (35 patients) were analyzed. OCT-A was performed before and after a single dialysis session. We performed OCT-A 3 × 3 mm and 6 × 6 mm scanning area focused on the fovea centralis. Patients were then followed up to 30 days (10 HD sessions) and a total of 73 IDHs were recorded, with 12 patients (60%) experiencing at least one IDH. Different OCT-A parameters were reduced after dialysis: central choroid thickness (CCT), 6 × 6 mm foveal whole vessel density (VD) of superficial capillary plexus (SPC) and 6 × 6 mm foveal VD of deep capillary plexus (DCP). At logistic regression analysis, IDH was positively associated with baseline foveal VD of SCP and DCP, while an inverse association was found with the choroid. In Kaplan–Meier analyses of patients categorized according to the ROC-derived optimal thresholds, CCT, the 3 × 3 foveal VD of SCP, the 3 × 3 mm and 6 × 6 mm foveal VD of DCP and the 6 × 6 mm foveal VD of SCP were strongly associated with a higher risk of IDH over the 30-days follow-up. In HD patients, a single OCT-A measurement may represent a non-invasive, rapid tool to evaluate the compliance of vascular bed to HD stress and to stratify the risk of IDH in the short term.

Evaluation of the different thresholding strategies for quantifying choriocapillaris using optical coherence tomography angiography

BACKGROUND

In this paper, we evaluate the different thresholding strategies that have been used for the quantification of the choriocapillaris (CC) and explore their repeatability and the interchangeability of the measurements resulting from its application.

METHODS

Observational study. Eighteen eyes from nine healthy volunteers aged >18 years were imaged four consecutive times with a SD-OCTA system (Heidelberg Engineering, Germany) using a 10°×10° high-resolution protocol centered on the fovea. Projection artifacts were removed, and the CC was bracketed between 10 and 30 µm below Bruch's membrane. For the quantification of CC, we used four flow deficits (FD) parameters: FD number, mean FD size, total FD area and FD density. We performed a systematic review of literature to collect the thresholding methods that have been used for the quantification of CC. The CC quantification parameters were then evaluated after applying each of the thresholding strategies. Intraclass correlation coefficient (ICC) and Pearson's correlation analysis were used to compare the repeatability and interchangeability among the different thresholding strategies for quantifying the CC.

RESULTS

A total of 72 optical coherence tomography angiography (OCTA) examinations were considered. The systematic review allowed us to conclude that three local thresholding strategies (Phansalkar, mean and Niblack) and three global thresholding strategies (mean, default, Otsu) have been used for CC quantification. These strategies were evaluated in our observational study. We found a high agreement within the same method in the quantification of FD number, mean FD size, total FD area and FD density but a poor agreement with different strategies. Local strategies achieved a significantly superior ICC than global ones in CC quantification.

CONCLUSIONS

In conclusion, the interchangeability of the CC quantification using different thresholding strategies is low, and direct comparisons should not be performed. Local thresholding strategies are significantly superior to global ones for quantifying CC and should be preferred. There is an unmet need for a uniform strategy to quantify CC in future studies.

The eye, the kidney, and cardiovascular disease: old concepts, better tools, and new horizons

Chronic kidney disease (CKD) is common, with hypertension and diabetes mellitus acting as major risk factors for its development. Cardiovascular disease is the leading cause of death worldwide and the most frequent end point of CKD. There is an urgent need for more precise methods to identify patients at risk of CKD and cardiovascular disease. Alterations in microvascular structure and function contribute to the development of hypertension, diabetes, CKD, and their associated cardiovascular disease. Homology between the eye and the kidney suggests that noninvasive imaging of the retinal vessels can detect these microvascular alterations to improve targeting of at-risk patients. Retinal vessel-derived metrics predict incident hypertension, diabetes, CKD, and cardiovascular disease and add to the current renal and cardiovascular risk stratification tools. The advent of optical coherence tomography (OCT) has transformed retinal imaging by capturing the chorioretinal microcirculation and its dependent tissue with near-histological resolution. In hypertension, diabetes, and CKD, OCT has revealed vessel remodeling and chorioretinal thinning. Clinical and preclinical OCT has linked retinal microvascular pathology to circulating and histological markers of injury in the kidney. The advent of OCT angiography allows contrast-free visualization of intraretinal capillary networks to potentially detect early incipient microvascular disease. Combining OCT's deep imaging with the analytical power of deep learning represents the next frontier in defining what the eye can reveal about the kidney and broader cardiovascular health.

Assessment of Retinal Microangiopathy in Chronic Kidney Disease Patients

INTRODUCTION

Optical coherence tomography angiography (OCT-A) is a useful diagnostic tool for assessing eyes' health in patients with chronic diseases, such as diabetes, hypertension, Parkinson's disease and chronic kidney disease (CKD).

AIM

To detect changes in macular structure and retinal vascular meshwork in the macular area and peripapillary in patients with chronic kidney disease (CKD).

METHODS

This cross-sectional study included 80 eyes of patients with CKD in stages 2, 3 or 4, who were followed-up in the Nephrology Clinic of University Clinical Center Sarajevo. All patients were categorized according to the stage of CKD. All patients were scanned by a high-speed 840-nm-wavelength spectral-domain optical coherence tomography instrument (RTVue XR Avanti; Optovue, Inc, Fremont, California, USA). Blood flow was detected using a split-spectrum amplitude-decorrelation angiography algorithm. A fully automated microstructural analysis of the foveal avascular zone (FAZ), FAZ perimeter, foveal vessel density in a 300-μm area around the FAZ (FD), nonflow area, flow index in superficial and deep vascular plexus, choriocapillary flow, vascular density, radial peripapillary capillary density was performed.

RESULTS

When comparing patients with CKD stage 2 and stage 3 there were no statistically significant changes in microvascular parameters on OCT angiography, as well as when comparing patients with CKD stage 3 and stage 4. But in the comparison between patients with less developed CKD (stage 2) and terminal CKD (stage 4) there was a significant difference between some microvascular parameters such as FAZ area, FAZ perimeter, choriocapillary flow.

CONCLUSION

Many studies demonstrated that evaluation of the microvascular changes in different retinal layers using SS-OCTA may be considered as a key to assessing the systemic perfusion status. Evaluation of retinal microvasculature may ease the management and approach of patients with CKD, having in mind that the retinal and the kidney vascular network are, concerning structure, development and the function, very similar.

Quantitative analysis of retinal and choroidal microvascular parameters using optical coherence tomography angiography in children with nephrotic syndrome: a pilot study

PURPOSE

To study the retinal and choroidal microvascular parameters in children with nephrotic syndrome (NS).

METHODS

This is a cross-sectional study. Optical coherence tomography angiography was used to evaluate the changes of retinal and choroidal microvessels in patients with NS. Thirty NS children and 20 normal controls were included in this study. The macular vessel density (VD) of the superficial capillary plexus (SCP), deep capillary plexus (DCP), choroid capillary plexus (CCP), and foveal avascular zone (FAZ) area of the SCP and DCP was quantitatively calculated. Clinical data including serum protein, blood lipid, uric acid, urea, serum creatinine, urinary protein concentration, urinary creatinine, 24-h urine volume, 24-h urinary total protein, 24-h creatinine clearance rate, and urinary albumin to creatinine ratio were collected.

RESULTS

The VDs of the DCP and CCP in children with NS were significantly lower than those in controls (59.35 ± 2.45 vs. 61.15 ± 1.53, p = 0.002, 66.34 ± 1.43 vs. 67.16 ± 1.23, p = 0.042, respectively). The VD of the SCP in children with NS had a tendency to decrease compared with that in controls, but there were no significant differences. There were also no significant differences in FAZ area between the two groups. The VD of the SCP was positively correlated with serum total protein (ρ = 0.446, p = 0.014), serum albumin (ρ = 0.431, p = 0.017), and 24-h urine volume (ρ = 0.389, p = 0.034) but negatively correlated with triglyceride (ρ = - 0.450, p = 0.013), low-density lipoprotein cholesterol (ρ = -0.432, p = 0.017), urinary protein concentration (ρ = - 0.606, p < 0.001), and 24-h urinary total protein (ρ = - 0.517, p = 0.004). The VDs of the SCP, DCP, and CCP were negatively correlated with the urinary albumin to creatinine ratio (ρ = - 0.473, p = 0.008, ρ = - 0.438, p = 0.015, ρ = -0.467, p = 0.009, respectively).

CONCLUSIONS

Retinal and choroidal VDs were decreased in children with NS and paralleled the severity of kidney disease. Optical coherence tomography angiography can be used as a noninvasive method for evaluating renal injury in patients with NS.

Comparison of Choroidal Thickness Measurements Using Spectral Domain Optical Coherence Tomography in Six Different Settings and With Customized Automated Segmentation Software

Purpose

We investigate which spectral domain-optical coherence tomography (SD-OCT) setting is superior when measuring subfoveal choroidal thickness (CT) and compared results to an automated segmentation software.

Methods

Thirty patients underwent enhanced depth imaging (EDI)-OCT. B-scans were extracted in six different settings (W+N = white background/normal contrast 9; W+H = white background/maximum contrast 16; B+N = black background/normal contrast 12; B+H = black background/maximum contrast 16; C+N = Color-encoded image on black background at predefined contrast of 9, and C+H = Color-encoded image on black background at high/maximal contrast of 16), resulting in 180 images. Subfoveal CT was manually measured by nine graders and by automated segmentation software. Intraclass correlation (ICC) was assessed.

Results

ICC was higher in normal than in high contrast images, and better for achromatic black than for white background images. Achromatic images were better than color images. Highest ICC was achieved in B+N (ICC = 0.64), followed by B+H (ICC = 0.54), W+N, and W+H (ICC = 0.5 each). Weakest ICC was obtained with Spectral-color (ICC = 0.47). Mean manual CT versus mean computer estimated CT showed a correlation of r = 0.6 (P = 0.001).

Conclusion

Black background with white image at normal contrast (B+N) seems the best setting to manually assess subfoveal CT. Automated assessment of CT seems to be a reliable tool for CT assessment.

Translational Relevance

To define optimized OCT analysis settings to improve the evaluation of in vivo imaging.

Normative pattern and determinants of outer retinal thickness in an Asian population: the Singapore Epidemiology of Eye Diseases Study

BACKGROUND/AIMS

To evaluate the distribution and determinants of outer retinal thickness in eyes without retinal diseases, using spectral-domain optical coherence tomography (SD-OCT).

METHODS

Participants were recruited from the Singapore Epidemiology of Eye Diseases Study, a population-based study among Chinese, Malays and Indians in Singapore. A total of 5333 participants underwent SD-OCT imaging in which a 6×6 mm² measurement area centred at the fovea. Outer retinal thickness was defined as the distance from the outer plexiform layer to the retinal pigment epithelium layer boundary.

RESULTS

7444 eyes from 4454 participants were included in final analysis. Of them, mean age was 58.4 years (SD 8.3), and 2294 (51.5%) were women. Women (121.0±8.1 µm) had thinner average outer retinal thickness than men (125.6±8.2 µm) (p<0.001). Malays (121.4±8.7 µm) had thinner average outer retinal thickness than Indians (124.3±8.6 µm) and Chinese (123.7±7.9 µm) (both p<0.001). In multivariable models, thinner average outer retinal thickness was associated with older age (per decade, β=-1.02, p<0.001), hypertension (β=-0.59, p=0.029), diabetes (β=-0.73, p=0.013), chronic kidney disease (β=-1.25, p=0.017), longer axial length (per mm, β=-0.76, p<0.001), flatter corneal curvature (per mm, β=-2.00, p<0.001) and higher signal strength (β=-1.46, p<0.001).

CONCLUSION

In this large sample of Asian population, we provided normative SD-OCT data on outer retinal thickness in eyes without retinal diseases. Women had thinner outer retina than men. For the first time, these findings provide fundamental knowledge on normative profile of outer retinal thickness in Asians.

Optical coherence tomography angiography analysis of changes in the retina and the choroid after haemodialysis

The purpose of this study is to evaluate the effect of haemodialysis on perfused vessel density, choroidal thickness (CT), and retinal thickness in end-stage renal disease (ESRD) using swept-source optical coherence tomography angiography (SS-OCTA). We studied twenty-nine eyes of 29 ESRD patients by ophthalmologic examination and SS-OCTA before and after haemodialysis. The colour-coded perfusion density maps were generated and perfused vessel density was calculated. Changes in systemic and other ocular parameters such as retinal and choroidal thickness were measured and analysed. Total perfused vessel density decreased significantly after haemodialysis in the choriocapillaris; it was not significantly different in the superficial capillary plexus (SCP) and the deep capillary plexus (DCP). Total CT decreased significantly, but total retinal thickness was not significantly different. There was no significant correlation between choriocapillaris perfused vessel density and CT. The reduction in choriocapillaris perfused vessel density correlated with the decrease in systolic and mean arterial blood pressures. The decrease in CT correlated with the ultrafiltration volume. There were no significant systemic and ocular factors affecting change in retinal thickness and perfused vessel density of SCP and DCP. This is the first study to assess the effect of haemodialysis on blood flow changes using SS-OCTA; changes may be more prominent in the choroidal compared to the retinal layer.