Influence of retinopathy on the achromatic and chromatic vision of patients with type 2 diabetes

Achromatic and chromatic contrast discrimination in patients with type 2 diabetes

Effects of type 2 diabetes on achromatic and chromatic contrast sensitivity (CS) are still controversial. In this study, we aimed to investigate CS in patients without diabetic retinopathy (no-DR) and in those with non-proliferative DR (NPDR) and proliferative DR (PDR) using psychophysical methods with transient and sustained achromatic stimuli and color patches. Achromatic CS was measured with the pulsed pedestal (PP) paradigm (7, 12, and 19 cd/m²) and pedestal-△-pedestal (P-△-P) paradigm (11.4, 18, and 28.5 cd/m²). A chromatic discrimination paradigm that assesses protan, deutan, and tritan color vision was adopted. Forty-two patients (no-DR n = 24, NPDR n = 12, PDR = 6; male n = 22, mean age = 58.1 y/o) and 38 controls (male n = 18, mean age = 53.4 y/o) participated. In patients, mean thresholds were higher than in controls and linear trends were significant in most conditions. For the PP paradigm, differences were significant in the PDR and NPDR groups in the 7 and 12 cd/m² condition. For the P-△-P paradigm, differences were only significant in the PDR group in the 11 cd/m² condition. Chromatic contrast loss was significant in the PDR group along the protan, deutan and tritan axes. The results suggest independent involvements of achromatic and chromatic CS in diabetic patients.

Retinal neurodegeneration in patients with type 2 diabetes mellitus without diabetic retinopathy

In diabetes mellitus (DM) patients retinal complications were typically considered part of a vascular process. Recent research suggests that retinal degeneration in DM might also be caused by a neuropathy that could precede microvascular alterations. The present work reviews the currently available bibliography about neurodegeneration in patients with type 2 DM (DM2) without diabetic retinopathy (DR). In patients with non-severe, early DM2 without DR and good metabolic control visual function parameters show early abnormalities that precede clinical DR (in which we diagnose with a conventional ophthalmological examination). Using optical coherence tomography (OCT) technology, a reduction in macular and peripapillary thickness has been observed in different studies. Recent researches suggest that systemic complications (especially ischaemia) and a possible microvascular alteration eventually contributes to retinal neurodegeneration, which opens the door to new studies that include new techniques for evaluating the microvascularization of the retinal layers.

The Investigation of the Effect of Hyperglycemic Changes on Psychophysical Measurements of Visual Function in Pseudophakic People Living with Diabetes Mellitus

PURPOSE

The purpose of this study was to show the effect of increasing blood glucose level (BGL) on psychophysical visual function represents by visual acuity and contrast sensitivity in pseudophakic people living with diabetes (PDM).

STUDY DESIGN

This was quasi-experimental, quantitative study using a pretest-posttest approach.

METHODS

The study was conducted at Gamalakhe community health centre located in Gamalakhe township and included a sample of 50 pseudophakic people living without diabetes mellitus (PWDM) and 50 pseudophakic PDM. BGL as well as psychophysical measurements of visual function were measured preprandial and postprandial. Visual acuity (VA) was measured at distance (4 m) and near (40 cm) using logMAR VA charts, and contrast sensitivity (CS) was measured at 50 cm using a Mars chart. The data collected were captured and subsequently analyzed using SPSS version 25.

RESULTS

Glycemic changes measured preprandial and postprandial observed a mean increase of 2.06±1.35 mmol/L (p=0.350) and 1.08±0.47 mmol/L (p=0.291) in pseudophakia PDM and pseudophakic PWDM, respectively. CS showed a mean increase of 0.01±0.10 (p=0.23) and 0.002±0.02 (p=0.19) log units in PDM and PWDM, respectively; however, the independent t-test showed this was insignificant between PDM and PWDM (p=0.27). A insignificant mean increase of 0.01±0.04 log units (p=0.25) and 0.001±0.01 (p=0.32) in distance VA of pseudophakic PDM and PWDM was found, respectively. A mean increase of 0.001±0.01 log units (p=0.32) and 0.01±0.03 (p=0.06) near logMAR VA of pseudophakic PDM and PWDM was found, respectively.

CONCLUSION

Acute hyperglycemic changes do not result in overall significant changes in visual acuity and contrast sensitivity in pseudophakic PDM and PWDM for an increase in glycemia of 2 mmol/L. We recommend studies investigate if changes occur for glycemic increases exceeding 2 mmol/L.

The Predictive Role of Thyroid Hormone Levels for Early Diabetic Retinal Changes in Experimental Rat and Human Diabetes

Purpose

In diabetic subjects, early visual functional alterations such as color vision deficiencies (CVDs) are known to precede clinically apparent diabetic retinopathy. Prominent photoreceptor outer segment degeneration and an increase in the number of retinal dual cones (co-expressing S- and M-opsins simultaneously) have been described in diabetic rat models, suggesting a connection with the development of CVDs. As cone opsin expression is controlled by thyroid hormones, we investigated the diabetic retina in association with thyroid hormone alterations.

Methods

In rat models of type 1 and 2 diabetes, dual cones were labeled by immunohistochemistry, and their numbers were analyzed in relation to free triiodothyronine (fT3) and free thyroxine (fT4) levels. Quantification of dual cones was also performed in human postmortem retinas. Additionally, a cross-sectional case–control study was performed where thyroid hormone levels were measured and color vision was assessed with Lanthony desaturated D15 discs.

Results

A higher number of dual cones was detectable in diabetic rats, correlating with fT4 levels. Dual cones were also present in postmortem human retinas, with higher numbers in the three diabetic retinas. As expected, age was strongly associated with CVDs in human patients, and the presence of diabetes also increased the risk. However, the current study failed to detect any effect of thyroid hormones on the development of CVDs.

Conclusions

Our results point toward the involvement of thyroid homeostasis in the opsin expression changes in diabetic rats and human samples. The evaluation of the possible clinical consequences warrants further research.

Prediabetes influences the structure of the macula: thinning of the macula in the Northern Finland Birth Cohort

BACKGROUND/AIM

The aim of this study was to evaluate the effect of prediabetes and diabetes on macular thickness and retinal vascular calibres in our population-based cohort (Northern Finland Birth Cohort).

METHODS

The population of 2005 individuals was divided into diabetes (n=57), prediabetes (n=1638) and normal glucose metabolism (NGM) groups (n=310). Total thickness of the macula was measured using Cirrus HD-OCT 4000. Central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) calibres were measured from the fundus images. The diagnosis of diabetes and prediabetes was made according to WHO 2006 diagnostic standards.

RESULTS

Significant macular thinning was observed in subjects with prediabetes (-2.69 μm (95% CI -4.29 to -1.09), p<0.05 and -0.10 mm³ (95% CI -0.16 to -0.04), p<0.05 for macular cube average thickness and cube volume, respectively) and it was greatest in the pericentral area. Macular cube average thickness and macular cube volume decreased significantly by worsening glucose metabolism. Furthermore, CRAE was decreased by increases in 2-hour post-load glucose, glucose area under the curve and increase in Matsuda index (p<0.001, 0.019 and <0.001, respectively). In mediation analysis, macular thickness had significant average causal mediation effect (ACME) on CRVE and CRAE in subjects with prediabetes.

CONCLUSION

We detected significant thinning of the macula in subjects with prediabetes. The diameters of retinal arteries were decreased by impaired glucose metabolism. This study provides a new perspective since it revealed that the early and subtle changes caused by prediabetes as macular thinning had significant ACME on retinal vessels, therefore supporting the neurodegenerative theory of diabetes-induced changes in the retina.

A critical review: Psychophysical assessments of diabetic retinopathy

Diabetic retinal disease remains a leading cause of vision loss despite currently available screening methods, ocular treatments, and efforts to control metabolic dysfunction. It is now understood that diabetes damages the entire retina and the cellular components of the neurovascular unit. Multiple studies have demonstrated impairment of various aspects of retinal function across the spectrum of retinopathy severity. Here we review these tests, the principles underlying their use, clinical data from multiple publications, the strengths and limitations of the studies, and prospects for their application to understand the pathophysiology of diabetic retinal disease and monitor its response to therapy. We focus on visual acuity, contrast sensitivity, color vision, visual field, and dark adaptation and their use to understand the pathophysiology of diabetic retinopathy and as potential endpoints for clinical trials.

Neuroinflammation and oxidative stress act in concert to promote neurodegeneration in the diabetic retina and optic nerve: galectin-3 participation

Diabetes is a lifelong disease characterized by glucose metabolic imbalance, in which low insulin levels or impaired insulin signaling lead to hyperglycemic state. Within 20 years of diabetes progression, 95% of patients will have diabetic retinopathy, the leading cause of visual defects in working-age people worldwide. Although diabetes is considered a microvascular disease, recent studies have shown that neurodegeneration precedes vascular changes within the diabetic visual system, albeit its mechanisms are still under investigation. Neuroinflammation and oxidative stress are intrinsically related phenomena, since macrophage/microglia and astrocytes are the main sources of reactive oxygen species during central nervous system chronic degenerative diseases, and both pathological processes are increased in the visual system during diabetes. The present review will focus on recent findings of the contribution of oxidative stress derived from neuroinflammation in the early neurodegenerative aspects of the diabetic visual system and their relationship with galectin-3.

A review of glycaemic changes on vision in phakic, aphakic and pseudophakic people with diabetes

Background: One of the leading causes of preventable blindness is cataract affecting approximately 18 million people worldwide. Twenty per cent of cataract operations worldwide are performed on people with diabetes mellitus (PDM).Aim: The aim of this review article is to analyse the scientific literature relating to visual changes associated with diabetes mellitus (DM) in pseudophakic, aphakic and phakic people, and to discuss the consequences of these changes for optometrists.Method: A literature search was conducted on PubMed, the University of KwaZulu-Natal Libraries and Google Scholar databases from August 2017 to August 2018.Results: Acute and chronic hyperglycaemia in DM causes myopia in phakic PDM, whilst in aphakic PDM it causes a hyperopic shift in refraction. It has been reported that contrast sensitivity and visual acuity are affected by changes in blood glucose. People with DM have increased central corneal thickness as compared to non-diabetics, whilst only the posterior corneal curvature is affected by hyperglycaemia in PDM. No evidence exists on the effects of glycaemic changes in pseudophakes.Conclusion: It should be noted that high blood glucose level (BGL) induces transient myopia and hyperopia in chronic phakic PDM and aphakic PDM, respectively. All refractive procedures, including prescription of spectacles, corneal refractive procedures and lens extraction, should be deferred until normalisation of BGL in phakic and pseudophakic PDM, as higher sugar levels affect corneal curvature and thickness and overall vision.

Spatial contrast sensitivity: effects of reliability, test-retest repeatability and sample size using the Metropsis software

PURPOSE

The goals of the study were to further assess contrast sensitivity to (1) investigate the existence of monocular vs. binocular differences; (2) observe possible differences between sample sizes; (3) investigate the effects of test-retest repeatability.

METHODS

Contrast sensitivity measurements were obtained by presenting eight horizontal sine-wave gratings (ranging from 0.2 to 20 cycles per degree). A three-up-one-down method was used to obtain thresholds with a criterion of 79.4% correct responses for each spatial frequency. The mean of 12 reversals was used for obtaining thresholds, and the two-alternative forced-choice method was used. Data were recorded in 55 naive observers from 20 to 45 years. All participants were free from identifiable ocular disease and had normal visual acuity.

RESULTS

We observed the absence of differences on CSF for both monocular and binocular observers, as well as the absence of differences between large sample sizes. The latter investigation revealed a high degree of repeatability across time (baseline to 6 months later) with the higher test-retest for low and high spatial frequencies.

CONCLUSIONS

Our results indicated that spatial contrast sensitivity measurements were little influenced by variables, such as binocular summation, eye dominance, sample size and time using the Metropsis test. The results obtained here have significance for basic and clinical vision science.

Role of ω3 polyunsaturated fatty acids in diabetic retinopathy: a morphological and metabolically cross talk among blood retina barriers damage, autoimmunity and chronic inflammation

Vision disorders are one of the most serious complications of diabetes mellitus (DM) affecting the quality of life of patients and eventually cause blindness. The ocular lesions in diabetes mellitus are located mainly in the blood vessels and retina layers. Different retina lesions could be grouped under the umbrella term of diabetic retinopathies (DMRP).

We propose that one of the main causes in the etiopathogenesis of the DMRP consists of a progressive loss of the selective permeability of blood retinal barriers (BRB). The loss of selective permeability of blood retinal barriers will cause a progressive autoimmune process. Prolonged autoimmune injures in the retinal territory will triggers and maintains a low-grade chronic inflammation process, microvascular alterations, glial proliferation and subsequent fibrosis and worse, progressive apoptosis of the photoreceptor neurons.

Patients with long-standing DM disturbances in retinal BRBs suffer of alterations in the enzymatic pathways of polyunsaturated fatty acids (PUFAs), increase release of free radicals and pro-inflammatory molecules and subsequently incremented levels of vascular endothelial growth factor. These facts can produce retinal edema and photoreceptor apoptosis.

Experimental, clinical and epidemiological evidences showing that adequate metabolic and alimentary controls and constant practices of healthy life may avoid, retard or make less severe the appearance of DMRP. Considering the high demand for PUFAs ω3 by photoreceptor complexes of the retina, it seems advisable to take fish oil supplements (2 g per day). The cellular, subcellular and molecular basis of the propositions exposed above is developed in this article.

Synthesizer drawings the most relevant findings of the ultrastructural pathology, as well as the main metabolic pathways of the PUFAs involved in balance and disbalanced conditions are provided.

Retinal Neurodegeneration as an Early Manifestation of Diabetic Eye Disease and Potential Neuroprotective Therapies

PURPOSE OF REVIEW

Diabetic retinopathy (DR) is a major cause of visual impairment and blindness throughout the world. Microvascular changes have long been regarded central to disease pathogenesis. In recent years, however, retinal neurodegeneration is increasingly being hypothesized to occur prior to the vascular changes classically associated with DR and contribute to disease pathogenesis.

RECENT FINDINGS

There is growing structural and functional evidence from human and animal studies that suggests retinal neurodegeneration to be an early component of DR. Identification of new therapeutic targets is an ongoing area of research with several different molecules undergoing testing in animal models for their neuroprotective properties and for possible use in humans. Retinal neurodegeneration may play a central role in DR pathogenesis. As new therapies are developed, it will be important to develop criteria for clinically defining retinal neurodegeneration. A standardization of the methods for monitoring neurodegeneration along with more sensitive means of detecting preclinical damage is also needed.

Multidimensional Functional and Structural Evaluation Reveals Neuroretinal Impairment in Early Diabetic Retinopathy

Purpose

To test whether quantitative functional tests and optical coherence tomography (OCT)-defined structure can serve as effective tools to diagnose and monitor early diabetic neuroretinal disease.

Methods

Fifty-seven subjects with diabetes (23 without diabetic retinopathy [no DR], 19 with mild nonproliferative diabetic retinopathy [mild NPDR], 15 with moderate to severe [moderate NPDR]), and 18 controls underwent full ophthalmic examination, fundus photography, spectral-domain optical coherence tomography (SD-OCT), e-ETDRS (Early Treatment Diabetic Retinopathy Study) acuity, and the quick contrast sensitivity function (qCSF) method. Perimetry testing included short-wavelength automated perimetry (SWAP), standard automated perimetry (SAP), frequency doubling perimetry (FDP), and rarebit perimetry (RBP).

Results

ETDRS acuity and RBP were not sensitive for functional differences among subjects with diabetes. AULCSF, a metric of qCSF, was reduced in diabetics with moderate compared to mild NPDR (P = 0.03), and in subjects with no DR compared to controls (P = 0.04). SWAP and SAP mean deviation (MD) and foveal threshold (FT) were reduced in moderate compared to mild NPDR (SWAP, MD P = 0.002, FT P = 0.0006; SAP, MD P = 0.02, FT P = 0.007). FDP 10-2 showed reduced MD in moderate compared to mild NPDR (P = 0.02), and FDP 24-2 revealed reduced pattern standard deviation (PSD) in mild NPDR compared to no DR (P = 0.02). Structural analysis revealed thinning of the ganglion cell layer and inner plexiform layer (GCL+IPL) of moderate NPDR subjects compared to controls. The thinner GCL+IPL correlated with impaired retinal function.

Conclusions

This multimodal testing analysis reveals insights into disruption of the neuroretina in diabetes and may accelerate the testing of novel therapies.

Inhibition of Stat3 by a Small Molecule Inhibitor Slows Vision Loss in a Rat Model of Diabetic Retinopathy

Purpose

Diabetic retinopathy is a leading cause of vision loss. Previous studies have shown signaling pathways mediated by Stat3 (signal transducer and activator of transcription 3) play a primary role in diabetic retinopathy progression. This study tested CLT-005, a small molecule inhibitor of Stat3, for its dose-dependent therapeutic effects on vision loss in a rat model of diabetic retinopathy.

Methods

Brown Norway rats were administered streptozotocin (STZ) to induce diabetes. CLT-005 was administered daily by oral gavage for 16 weeks at concentrations of 125, 250, or 500 mg/kg, respectively, beginning 4 days post streptozotocin administration. Systemic and ocular drug concentration was quantified with mass spectrometry. Visual function was monitored at 2-week intervals from 6 to 16 weeks using optokinetic tracking to measure visual acuity and contrast sensitivity. The presence and severity of cataracts was visually monitored and correlated to visual acuity. The transcription and translation of multiple angiogenic factors and inflammatory cytokines were measured by real-time polymerase chain reaction and Multiplex immunoassay.

Results

Streptozotocin-diabetic rats sustain progressive vision loss over 16 weeks, and this loss in visual function is rescued in a dose-dependent manner by CLT-005. This positive therapeutic effect correlates to the positive effects of CLT-005 on vascular leakage and the presence of inflammatory cytokines in the retina.

Conclusions

The present study indicates that Stat3 inhibition has strong therapeutic potential for the treatment of vision loss in diabetic retinopathy.

Factors associated with impaired color vision without retinopathy amongst people with type 2 diabetes mellitus: a cross-sectional study

BACKGROUND

Patients with type 2 diabetes mellitus (T2DM) may develop color vision impairment. This study aimed to determine the prevalence and factors associated with impaired color vision in patients with T2DM but without diabetic retinopathy.

METHODS

Enrolment criteria included multi-ethnic Asian participants, age 21 to 80 years, with known T2DM for a minimum of 2 years. Their diagnoses were affirmed from oral glucose tolerance test results and they were screened for impaired color vision using the Farnsworth D-15 instrument. Demographic characteristics were described and clinical data for the preceding 2 years were analyzed using logistic regression.

RESULTS

Twenty-two percent of 849 eligible participants had impaired color vision with higher involvement of the right eye. Impaired blue-yellow color-vision(Tritanomaly) was the commonest impaired color vision. Participants with impaired color vision were significantly associated with age and lower education; longer duration of T2DM (median 6 years vs 4 years); higher HbA1c level and HDL-Cholesterol in 2nd year; lower mean total cholesterol, mean LDL-Cholesterol and mean triglyceride in 2nd year. They also have poorer vision beyond 6/12 in the affected eye. Logistic regression showed that impaired color vision was associated with older patients (OR=1.04), increased duration of T2DM (OR=1.07); prescription of Tolbutamide (OR=3.79) and lower mean systolic blood pressure (OR=0.98).

CONCLUSION

Almost one in four participants with T2DM had impaired color vision, largely with tritanomaly. Color vision screening may be considered for participants who develop T2DM for 6 years or longer, but this requires further cost-effectiveness evaluation.

Relations between Cardiac and Visual Phenotypes in Diabetes: A Multivariate Approach

Cardiovascular disease and diabetes represent a major public health concern. The former is the most frequent cause of death and disability in patients with type 2 diabetes, where left ventricular dysfunction is highly prevalent. Moreover, diabetic retinopathy is becoming a dominant cause of visual impairment and blindness. The complex relation between cardiovascular disease and diabetic retinopathy as a function of ageing, obesity and hypertension remains to be clarified. Here, we investigated such relations in patients with diabetes type 2, in subjects with neither overt heart disease nor advanced proliferative diabetic retinopathy. We studied 47 patients and 50 controls, aged between 45 and 65 years, equally distributed according to gender. From the 36 measures regarding visual structure and function, and the 11 measures concerning left ventricle function, we performed data reduction to obtain eight new derived variables, seven of which related to the eye, adjusted for age, gender, body mass index and high blood pressure using both discriminant analysis (DA) and logistic regression (LR). We found moderate to strong correlation between left ventricle function and the eye constructs: minimum correlation was found for psychophysical motion thresholds (DA: 0.734; LR: 0.666), while the maximum correlation was achieved with structural volume density in the neural retina (DA: 0.786; LR: 0.788). Controlling the effect of pairwise correlated visual constructs, the parameters that were most correlated to left ventricle function were volume density in retina and thickness of the retinal nerve fiber layers (adjusted multiple R² is 0.819 and 0.730 for DA and LR), with additional contribution of psychophysical loss in achromatic contrast discrimination. We conclude that visual structural and functional changes in type 2 diabetes are related to heart dysfunction, when the effects of clinical, demographic and associated risk factors are taken into account, revealing a genuine relation between cardiac and retinal diabetic phenotypes.

Targeting mitochondrial function to protect against vision loss

INTRODUCTION

Mitochondria, essential to multicellular life, convert food into ATP to satisfy cellular energy demands. Since different tissues have different energy requirements, mitochondrial density is high in tissues with high metabolic needs, such as the visual system, which is therefore highly susceptible to limited energy supply as a result of mitochondrial dysfunction.

AREAS COVERED

Vision impairment is a common feature of most mitochondrial diseases. At the same time, there is mounting evidence that mitochondrial impairment contributes to the pathogenesis of major eye diseases such as glaucoma and might also be involved in the reported vision impairment in neurodegenerative disorders such as Alzheimer's disease.

EXPERT OPINION

Rather than relying on symptomatic treatment, acknowledging the mitochondrial origin of visual disorders in mitochondrial, neurodegenerative and ocular diseases could lead to novel therapeutics that aim to modulate mitochondrial function in order to protect against vision loss. This approach has already shown some promising clinical results in inherited retinal disorders, which supports the idea that targeting mitochondria could also be a treatment option for other optic neuropathies.

Neuroprotection as a Therapeutic Target for Diabetic Retinopathy

Diabetic retinopathy (DR) is a multifactorial progressive disease of the retina and a leading cause of vision loss. DR has long been regarded as a vascular disorder, although neuronal death and visual impairment appear before vascular lesions, suggesting an important role played by neurodegeneration in DR and the appropriateness of neuroprotective strategies. Upregulation of vascular endothelial growth factor (VEGF), the main target of current therapies, is likely to be one of the first responses to retinal hyperglycemic stress and VEGF may represent an important survival factor in early phases of DR. Of central importance for clinical trials is the detection of retinal neurodegeneration in the clinical setting, and spectral domain optical coherence tomography seems the most indicated technique. Many substances have been tested in animal studies for their neuroprotective properties and for possible use in humans. Perhaps, the most intriguing perspective is the use of endogenous neuroprotective substances or nutraceuticals. Together, the data point to the central role of neurodegeneration in the pathogenesis of DR and indicate neuroprotection as an effective strategy for treating this disease. However, clinical trials to determine not only the effectiveness and safety but also the compliance of a noninvasive route of drug administration are needed.

Impairment of Colour Vision in Diabetes with No Retinopathy: Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular Genetics Study (SNDREAMS- II, Report 3)

PURPOSE

To assess impairment of colour vision in type 2 diabetics with no diabetic retinopathy and elucidate associated risk factors in a population-based cross-sectional study.

METHODS

This is part of Sankara Nethralaya Diabetic Retinopathy Epidemiology and Molecular-genetics Study (SN-DREAMS II) which was conducted between 2007-2010. FM 100 hue-test was performed in 253 subjects with no clinical evidence of diabetic retinopathy. All subjects underwent detailed ophthalmic evaluation including cataract grading using LOCS III and 45° 4-field stereoscopic fundus photography. Various ocular and systemic risk factors for impairment of colour vision (ICV) were assessed in subjects with diabetes but no retinopathy. P value of < 0.05 was considered statistically significant.

RESULTS

The mean age of the study sample was 57.08 ± 9.21 (range: 44-86 years). Gender adjusted prevalence of ICV among subjects with diabetes with no retinopathy was 39.5% (CI: 33.5-45.5). The mean total error score in the study sample was 197.77 ± 100 (range: 19-583). The risk factors for ICV in the study were women OR: 1.79 (1.00-3.18), increased resting heart rate OR: 1.04 (1.01-1.07) and increased intraocular pressure OR: 1.12 (1.00-1.24). Significant protective factor was serum high-density lipoprotein OR: 0.96 (0.93-0.99).

CONCLUSIONS

Acquired ICV is an early indicator of neurodegenerative changes in the retina. ICV found in diabetic subjects without retinopathy may be of non-vascular etiology.