Longitudinal study of visual functions in young insulin dependent diabetics

Visual function and retinal thickness in children with type 1 diabetes mellitus

CLINICAL RELEVANCE

The possibility that changes in blue-yellow visual thresholds and some retinal thickness measures in children with diabetes mellitus may be observed before any visible fundus changes points to the possibility of these measures being a useful predictor that the risks of diabetic retinopathy are higher in some children than in others.

INTRODUCTION

Previous studies showed mixed results on chromatic and achromatic contrast sensitivity early in the course of diabetes mellitus, and the findings of these studies may have been influenced by a lack of experimental sensitivity to visual deficits, a bias towards tritan-like errors or the cognitive demands of the tests and variations in sample composition. The purpose of this study was to evaluate colour and contrast thresholds and retinal thickness in children with type 1 diabetes mellitus compared with age-matched controls.

METHODS

A prospective case-control study was carried out on 9-14-year-old children with type 1 diabetes mellitus (49 cases) and age matched controls (49) in which isoluminant red-green and blue-yellow and achromatic luminance contrast thresholds were measured. Fundus photography was used to grade diabetic retinopathy. Retinal thickness parameters were measured using optical coherence tomography. Data on the duration of diabetes mellitus, glycaemic control (HbA1c), blood glucose level, body mass index, blood pressure and blood oxygenation at the time of testing were obtained.

RESULTS

The cases mostly had poorly controlled diabetes, HbA1c 8.6% (6.4-12.8%), for an average (range) duration of 5 (0.4-12) years. The cases had significantly higher blue-yellow thresholds (p = 0.02) and greater total retinal and inner retinal thickness (p < 0.05) than controls. No cases had diabetic retinopathy. Within the cases, poorer visual function and systemic health measures were associated with thinner retinal structures and greater global loss volume percentage in the ganglion cell complex.

CONCLUSION

Blue-yellow thresholds of cases were raised compared to normal. Within the cases, higher luminance contrast thresholds were also associated with, mostly, ganglion cell complex reductions.

PRE-RETINOPATHY OF TYPE 1 DIABETES IN THE CONTEXT OF FUNCTIONAL, STRUCTURAL AND MICROCIRCULATORY CHANGES IN THE MACULAR AREA

AIM

The authors assessed the development of intraocular changes in type 1 diabetes (T1DM) from the onset of the disease leading to diabetic retinopathy (DR). The quote: &#8220;There must be an intermediate stage between the physiological intraocular finding and the diabetic retinopathy itself &#8220;, (prof. Jan Vav&#345;inec).

METHODS

A two-year study (2018 and 2019) was conducted at the Department of Ophthalmology of the Teaching Hospital Kralovske Vinohrady in Prague (Czech Republic). There were 54 patients aged 17-42 years, the detection of T1DM ranged between the 1st and 14th year of life, with a duration of 12-35 years. Individual patients were always examined simultaneously by three methods: CS (contrast sensitivity), SD-OCT (spectral domain optical coherence tomography) and OCT-A (optical coherence tomography-angiography). We examined 106 eyes once and in a comprehensive manner.

RESULTS

We have shown that there is an intermediate stage between the physiological finding on the retina and DR, so-called diabetic pre-retinopathy (DpR). Subsequent redistribution of the observed into two DpR subgroups was derived from the size of the FAZ, either with its smaller area or with a larger area determining the microvascularity of the central area of the retina. The results of both other methods were assigned to these values. For SD-OCT, the depth of the fovea (the difference between the central retinal thickness and the total average retinal thickness) was determined, which was affected by the increased the macular cubature. In all patients it was on average 10.3 &#956;m3. The retina in the central area was significantly strengthened compared to the healthy population at the level of significance p 0,001. We divided the actual DpR into an image: DpR1 in 26.5 % of eyes - condition with an average shallower fovea only by 21.5 &#956;m below the level of the surrounding retina and an average narrower FAZ: 0.165 mm2 and with a more significant decrease in CS; DpR2 in 40.5 % of eyes - condition with average deeper fovea by 42 &#956;m, i.e., more significantly and average larger FAZ: 0.325 mm2 with lower decrease of CS. At the same time, other changes in microvascularity were noted, such as disorders in the sense of non-perfusion in the central part of the retina of various degrees. This finding differed significantly from changes in already established (non-proliferative) NPDR in 36 % of eyes, when a significant decrease in CS with normal visual acuity was found 4/4 ETDRS. Statistical differences in CS between DpR1 and DpR2 and NPDR were determined - always p 0.001. The average depth of the fovea was NPDR: 29.5 &#956;m. NPDR had the largest average FAZ: 0.56 mm2. Also significant were the most significant changes in non-perfusion and especially the presence of microaneurysms.

CONCLUSIONS

These three non - invasive methods helped to monitor the dynamics of the development of ocular changes in T1DM of better quality than the determination of visual acuity and ophthalmoscopic examination. Increased retinal volume induced hypoxia of visual cells with subsequent dual autoregulatory mechanism conditioning two types of diabetic pre-retinopathy before the onset of DR.

Photoreceptor cells and RPE contribute to the development of diabetic retinopathy

Diabetic retinopathy (DR) is a leading cause of blindness. It has long been regarded as vascular disease, but work in the past years has shown abnormalities also in the neural retina. Unfortunately, research on the vascular and neural abnormalities have remained largely separate, instead of being integrated into a comprehensive view of DR that includes both the neural and vascular components. Recent evidence suggests that the most predominant neural cell in the retina (photoreceptors) and the adjacent retinal pigment epithelium (RPE) play an important role in the development of vascular lesions characteristic of DR. This review summarizes evidence that the outer retina is altered in diabetes, and that photoreceptors and RPE contribute to retinal vascular alterations in the early stages of the retinopathy. The possible molecular mechanisms by which cells of the outer retina might contribute to retinal vascular damage in diabetes also are discussed. Diabetes-induced alterations in the outer retina represent a novel therapeutic target to inhibit DR.

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.

Are Contrast Sensitivity Functions Impaired in Insulin Dependent Diabetics Without Diabetic Retinopathy?

Purpose: To confirm the influence of multilevel metabolic disturbance of insulin dependent diabetes mellitus (IDDM) on the vision even before the onset of the other changes routinely evaluated by ophthalmologists. Methods: Contrast sensitivity functions (CSFs) were estimated using the VCTS 6500 board. The standardised measurement procedure was performed. The value of the threshold contrast sensitivity was obtained for five spatial frequencies (1.5 - 3 - 6 - 12 - 18 c/deg). Other data was collected (duration of diabetes, BCVA, funduscopy, fluoresceine angiography, HbA1C). The study group consisted of 48 IDDM patients (94 eyes) without diabetic retinopathy and with Snellen BCVA > 1.0. The control group (56 normals, 98 eyes) was age and BCVA matched. Results: Highly statistically significant decrease of the CSFs in all spatial frequencies in the study group was obtained. Correlation between duration of the diabetes and impaired degree of CSFs was present in the middle spatial frequency. No significant changes in CSFs were found among patients with pathological value of glycated hemoglobin HbA1c (>7.8 %). Conclusions: If compared with routinely used Snellen visual acuity, the CSFs are more complex descriptors of the subjects vision abilities. IDDM has an influence on these sensitive functions, especially during examination in the middle spatial frequency of 6 and 12 c/deg, before disturbing visual acuity and before changes in the retinal morphology. Decrease of CSFs was influenced mainly by the patients’ age and partially (in the middle spatial frequency) by the IDDM duration.

Reduced Contrast Sensitivity is Associated With Elevated Equivalent Intrinsic Noise in Type 2 Diabetics Who Have Mild or No Retinopathy

Purpose

To evaluate explanations for contrast sensitivity (CS) losses in subjects who have mild nonproliferative diabetic retinopathy (NPDR) or no diabetic retinopathy (NDR) by measuring and modeling CS in luminance noise.

Methods

Ten diabetic subjects with NDR, 10 with mild NPDR, and 10 age-equivalent nondiabetic controls participated. Contrast threshold energy (E_t) was measured for letters presented in the absence of noise (E_t0) and in four levels of luminance noise. Data were fit with the linear amplifier model to estimate inferred noise level within the visual pathway (N_eq) and sampling efficiency (ability to use stimulus information optimally). E_t0, N_eq, and efficiency were compared to clinical characteristics.

Results

N_eq was correlated with E_t0 for the diabetic subjects (r = 0.93, P < 0.001) and ranged from normal to 12-times the upper limit of normal. ANOVA indicated significant differences among the subject groups for E_t0 and N_eq (both F > 11.92, P < 0.001). E_t0 and N_eq were elevated for the mild NPDR group compared to the control and NDR groups (all t > 3.89, P ≤ 0.001); the NDR and control groups did not differ significantly (all t < 0.61, P > 0.55). There were no significant efficiency differences among the groups (F = 1.29, P = 0.29). N_eq was correlated significantly with disease duration, microperimetric sensitivity, and Pelli-Robson CS.

Conclusions

Elevated contrast threshold may be associated with increased intrinsic noise in early-stage diabetic subjects. Results suggest that noise-based CS measurements can provide important information about early neural dysfunction in these individuals.

Contrast sensitivity to spatial gratings in moderate and dim light conditions in patients with diabetes in the absence of diabetic retinopathy

OBJECTIVE

To evaluate the ability of contrast sensitivity (CS) to discriminate loss of visual function in diabetic subjects with no clinical signs of retinopathy relative to that of normal subjects.

RESEARCH DESIGN AND METHODS

In this prospective cross-sectional study, we measured CS in 46 diabetic subjects with a mean age of 48±6 years, a best-corrected visual acuity of 20/20 and no signs of diabetic retinopathy. The CS in these subjects was compared with CS measurements in 46 normal control subjects at four spatial frequencies (3, 6, 12, 18 cycles per degree) under moderate (500 lux) and dim (less than 2 lux) background light conditions.

RESULTS

CS was approximately 0.16 log units lower in patients with diabetes relative to controls both in moderate and in dim background light conditions. Logistic regression classification and receiver operating characteristic curve analysis indicated that CS analysis using two light conditions was more accurate (0.78) overall compared with CS analysis using only a single illumination condition (accuracy values were 0.67 and 0.70 in moderate and dim light conditions, respectively).

CONCLUSIONS

Our results showed that patients with diabetes without clinical signs of retinopathy exhibit a uniform loss in CS at all spatial frequencies tested. Measuring the loss in CS at two spatial frequencies (3 and 6 cycles per degree) and two light conditions (moderate and dim) is sufficiently robust to classify diabetic subjects with no retinopathy versus control subjects.

Retinylamine Benefits Early Diabetic Retinopathy in Mice

Recent evidence suggests an important role for outer retinal cells in the pathogenesis of diabetic retinopathy (DR). Here we investigated the effect of the visual cycle inhibitor retinylamine (Ret-NH2) on the development of early DR lesions. Wild-type (WT) C57BL/6J mice (male, 2 months old when diabetes was induced) were made diabetic with streptozotocin, and some were given Ret-NH2 once per week. Lecithin-retinol acyltransferase (LRAT)-deficient mice and P23H mutant mice were similarly studied. Mice were euthanized after 2 (WT and Lrat(-/-)) and 8 months (WT) of study to assess vascular histopathology, accumulation of albumin, visual function, and biochemical and physiological abnormalities in the retina. Non-retinal effects of Ret-NH2 were examined in leukocytes treated in vivo. Superoxide generation and expression of inflammatory proteins were significantly increased in retinas of mice diabetic for 2 or 8 months, and the number of degenerate retinal capillaries and accumulation of albumin in neural retina were significantly increased in mice diabetic for 8 months compared with nondiabetic controls. Administration of Ret-NH2 once per week inhibited capillary degeneration and accumulation of albumin in the neural retina, significantly reducing diabetes-induced retinal superoxide and expression of inflammatory proteins. Superoxide generation also was suppressed in Lrat(-/-) diabetic mice. Leukocytes isolated from diabetic mice treated with Ret-NH2 caused significantly less cytotoxicity to retinal endothelial cells ex vivo than did leukocytes from control diabetics. Administration of Ret-NH2 once per week significantly inhibited the pathogenesis of lesions characteristic of early DR in diabetic mice. The visual cycle constitutes a novel target for inhibition of DR.

Neural contrast sensitivity calculated from measured total contrast sensitivity and modulation transfer function

PURPOSE

To test the feasibility of calculating neural contrast sensitivity function (neural CSF) from conventionally measured total contrast sensitivity function (total CSF) and measured modulation transfer function (MTF). Neural CSF considers the retina and the brain, whereas total CSF considers the optical eye media, the retina and the brain together.

METHODS

We studied three groups comprising nine eyes each: one group with normal ocular optics but retinal alterations (mild diabetic retinopathy), one with altered ocular optics and normal retina (keratoconus), and a normal control group.

RESULTS

Total CSF in the keratoconus and retinopathy groups was significantly lower compared to the control group. Modulation transfer function for keratoconus was lower, and in the retinopathy group was similar to that of the control group. Calculated neural CSF in the diabetes mellitus group was lower than in the control group whereas in the keratoconus group it was similar to that of the control group, with overestimations for some keratoconus cases.

CONCLUSION

It is possible to calculate a meaningful neural CSF from measured total CSF and MTF data. The neural CSF represents a CSF adjusted for optical aberrations. This would allow comparison of the neural component of visual function in eyes with different optical aberrations.

Decreased contrast sensitivity in children and adolescents with type 1 diabetes mellitus

PURPOSE

To evaluate contrast sensitivity in children and adolescents with diabetes mellitus without evidence of diabetic retinopathy.

METHODS

Sixty patients with insulin-dependent diabetes mellitus (age range: 8 to 18 years) were studied. Their contrast sensitivity scores were obtained using the CSV-1000 device (Vector Vision, Dayton, OH) for four spatial frequencies and were compared with v scores of 45 age-matched and gender-matched "healthy" patients. Contrast sensitivity values were also correlated to patient's age, duration of disease, and metabolic control of diabetes mellitus.

RESULTS

The patients with insulin-dependent diabetes mellitus had a significant contrast sensitivity score reduction at all spatial frequencies tested. Glycosylated hemoglobin levels were inversely related to the contrast sensitivity thresholds. No significant correlation was found between the contrast sensitivity scores and the patient's age or duration of disease.

CONCLUSION

Contrast sensitivity defects are detected in patients with insulin-dependent diabetes mellitus. These defects may represent an early dysfunction of the retina, visual pathway, or both in patients with insulin-dependent diabetes mellitus who do not show any signs of diabetic retinopathy.

Assessment of central vision and macular structure in patients undergoing iodine-125 brachytherapy for ciliochoroidal melanoma

OBJECTIVES

To prospectively report standardized visual function and macular structural assessment in patients undergoing iodine-125 brachytherapy for choroidal and ciliary body melanoma.

MATERIALS AND METHODS

Patients were enrolled for pretreatment and annual posttreatment assessment. Evaluations included ophthalmic history; standardized refraction; visual acuity, contrast sensitivity, and color vision measurement; comprehensive ophthalmic examination; fundus photography; fluorescein angiography; optical coherence tomography; and ultrasonography. Radiation doses to the foveola and optic disc margin were calculated.

RESULTS

Forty-two patients were enrolled. Melanoma location included 3 in the ciliary body, 7 anterior, 11 equatorial, 13 posterior, and 8 macular tumors. Mean apical tumor height was 4.45 mm (range 1.79-9.83 mm) and mean longitudinal tumor diameter was 9.41 mm (range 4.52-4.73 mm). Pretreatment mean best-corrected Ferris-Bailey early treatment diabetic retinopathy study visual acuity was 50 (standard deviation +/- 15) letters (Snellen equivalent 20/32, range 20/15 to hand motions). The mean Pelli-Robson contrast threshold percentage was 4.1% (+/- 2.5%). The mean Hardy-Rand-Rittler color vision score was 13/14 (+/- 2.7). Mean distances from the posterior edge of the tumor to the foveola and the optic disc margin were 6.99 mm (+/- 6.22 mm) and 7.28 mm (+/- 5.98 mm), respectively. At the foveola, median total radiation dose was 36.2 Gy (+/-50.6 Gy) and median dose rate was 31.6 cGy/h (+/- 39.8 cGy/h). At the optic nerve, median total radiation dose was 42.8 Gy (+/- 30.8 Gy) and median dose rate was 36.2 cGy/h (+/- 21.4 cGy/h).

CONCLUSION

This prospective assessment of macular structure and function will provide more complete understanding of the ocular effects of radiation therapy for ocular melanoma.

Temporal visual filtering in diabetes mellitus

The background modulation method was used to investigate the temporal response of the magnocellular pathway in diabetic patients and controls. The luminance threshold for detecting a moving, 2 degrees, achromatic target was measured as a function of background flicker frequency from 5 to 45 Hz. A model of photoreceptor kinetics integrated with difference of Gaussian receptive fields [Vis. Neurosci. 13 (1996) 173] was used to analyse the data. Diabetic patients with significant maculopathy showed raised thresholds at 8.75, 12.5, 15 and 17.5 Hz. Estimates of photoreceptor summation time were the same in both groups, but receptive field centre-to-surround delay showed an increasing trend in the diabetic patients.

Seeing beyond retinopathy in diabetes: electrophysiological and psychophysical abnormalities and alterations in vision

Contrast sensitivity testing, in common with color vision (another test of psychophysical function), demonstrates significant changes in diabetic subjects compared with nondiabetic controls, and there is some evidence for a relationship with grade of retinopathy. Changes in contrast sensitivity have been demonstrated in children and adults with diabetes of short duration, and some evidence exists for a correlation with poor glycemic control, although prospective studies are required to assess this relationship over a longer time period. Although both color vision and contrast sensitivity demonstrate similar patterns, studies that directly compare the two tests suggest that measurement of contrast sensitivity is the more sensitive and specific.

Relationship between contrast sensitivity and metabolic control in diabetics with and without retinopathy

Contrast sensitivity was studied in diabetic adolescents and young adults with and without retinopathy in order to evaluate their central vision, to analyze the relationship of metabolic control to the presence and severity of retinopathy, and to re-evaluate the response to this test after a significant improvement in metabolic control. Twenty adolescent and young adult diabetics without retinopathy and 40 diabetics with retinopathy of varying degree were enrolled in the study; 20 healthy age and sex-matched subjects served as controls. Contrast sensitivity was assessed with a CSV-1000 contrast testing instrument, testing for four spatial frequencies, 3, 6, 12 and 18 cycles per degree (cpd). Diabetics with no retinopathy showed a weak but significant difference at 18 cpd compared with controls (P = 0.04), while diabetics with background retinopathy showed a significant reduction of contrast sensitivity at 12 and 18 cpd when compared with controls (P < 0.001). In patients with preproliferative/proliferative retinopathy a highly significant reduction of contrast sensitivity at all frequencies was found compared with controls. Furthermore, these patients had a significantly lower mean contrast sensitivity than patients without retinopathy. The patients were re-evaluated after a significant amelioration of metabolic control. An improvement in contrast sensitivity was found in diabetics without retinopathy and with background retinopathy, while there was no change observed in diabetics with severe retinopathy. These results show that diabetic adolescents and young adults with and without signs of retinopathy observed by fluorescein angiography have a reduced contrast sensitivity, which is more severe in patients with preproliferative/proliferative retinopathy. A significant amelioration of metabolic control is associated with an improvement of contrast sensitivity in all patients with the exception of those patients who had signs of preproliferative/proliferative retinopathy observed by fluorescein angiography. In summary, this longitudinal study provides the first evidence that reduced contrast sensitivity is reversible in diabetics with or without background retinopathy only.

Long-term tamoxifen citrate use and potential ocular toxicity

PURPOSE

To estimate the prevalence of abnormalities in visual function and ocular structures associated with the long-term use of tamoxifen citrate.

METHODS

A single-masked, cross-sectional study involving multiple community and institutional ophthalmologic departments was conducted with a volunteer sample of 303 women with breast cancer currently taking part in a randomized clinical trial to determine the efficacy of tamoxifen (20 mg/day) in preventing recurrences. Participants included women who had never been on drug (n=85); women who had taken tamoxifen for an average of 4.8 years, then been off the drug for an average of 2.7 years (n=140); and women who had been on tamoxifen continuously for an average of 7.8 years (n=78). Women were evaluated by questionnaire, psychophysical testing, and clinical examination to determine any abnormalities in visual function and the comparative prevalences of corneal, lens, retinal, and optic nerve pathology.

RESULTS

There were no cases of vision-threatening ocular toxicity among the tamoxifen-treated participants. Compared with nontreated participants, the tamoxifen-treated women had no differences in the activities of daily vision, visual acuity measurements, or other tests of visual function except for color screening. Intraretinal crystals (odds ratio [OR]=3.58, P=.178) and posterior subcapsular opacities (OR=4.03, P=.034) were more frequent in the tamoxifen-treated group.

CONCLUSIONS

Women should have a thorough baseline ophthalmic evaluation within the first year of initiating tamoxifen therapy and receive appropriate follow-up evaluations.

Contrast sensitivity in diabetic pregnancy

PURPOSE

To evaluate the correlation between the changes in contrast sensitivity and retinopathy throughout pregnancy in diabetic women with mild background diabetic retinopathy.

METHODS

Contrast sensitivity (Vistech 6500 Contrast Test System) was measured in 22 type I diabetic women with mild background retinopathy [0-16 microaneurysms (MAs)/eye and occasional small intraretinal hemorrhages] and 10 healthy pregnant women at the 12th and 32nd weeks of pregnancy and 3 months after delivery. Red-free fundus photography was also performed at all visits.

RESULTS

Throughout pregnancy contrast sensitivity was lower in the diabetics than in the controls at 1.5, 3.0, and 6.0 cycles per degree (cpd). During the course of pregnancy, contrast sensitivity decreased at 1.5 and 6.0 cpd in patients with more than five new MAs compared to those with fewer than five new MAs during pregnancy. Likewise, contrast sensitivity decreased at 6 cpd in patients with an increase in MA count during pregnancy and at 6 and 12 cpd in patients with a baseline MA count of two or more MAs.

CONCLUSIONS

Contrast sensitivity, especially at low to mid-range spatial frequencies, is decreased in diabetic women with mild retinopathy. Even small changes in retinopathy are reflected in a decrease in contrast sensitivity during and after pregnancy. Thus, contrast sensitivity seems to be a sensitive indicator of changes in minimal background retinopathy.