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

Visual motion sensitivity as an indicator of diabetic retinopathy in type 2 diabetes mellitus

Objectives

This current study is based on a set of visual motion sensitivity tests, investigating the correlation between visual motion sensitivity and diabetic retinopathy (DR) in type 2 diabetes mellitus (T2DM), thereby furnishing a scientific rationale for preventing and controlling DR.

Methods

This research was conducted by a combination of questionnaire collection and on-site investigation that involved 542 T2DM recruited from a community. The visual motion sensitivity determined the visual motion perception of the participants across three spatial frequencies (low, medium, and high) for both the first- and second-order contrast. The logistic regression model was adopted to investigate the relationship between visual motion sensitivity and DR prevalence. Besides, the Pearson correlation analysis was used to analyze the factors influencing visual motion sensitivity and restricted cubic spline (RCS) functions to assess the dose-response relationship between visual motion sensitivity and glycated hemoglobin.

Results

Among 542 subjects, there are 162 cases of DR, with a prevalence rate of 29.89%. After adjusting factors of age, gender, glycated hemoglobin, duration of diabetes, BMI, and hypertension, we found that the decline in first- and second-order high spatial frequency sensitivity increased the risk for DR [odds ratio (OR): 1.519 (1.065, 2.168), 1.249 (1.068, 1.460)]. The decline in perceptual ability of second-order low, medium, and high spatial frequency sensitivity is a risk factor for moderate to severe DR [OR: 1.556 (1.116, 2.168), 1.388 (1.066, 1.806), 1.476 (1.139, 1.912)]. The first-order and the second-order high spatial frequency sensitivity are significantly positively correlated with glycated hemoglobin (r = 0.105, p = 0.015 and r = 0.119, p = 0.005, respectively).

Conclusion

Visual motion sensitivity especially for the second-order high spatial frequency stimuli emerges as a significant predictor of DR in T2DM, offering a sensitive diagnostic tool for early detection.

Safety of repeated low-level red-light therapy for children with myopia

BACKGROUD

To investigate the safety of repetitive low-level red-light therapy (RLRLT) in children with myopia.

METHODS

Children with myopia were assigned to the RLRL and control groups. Axial length (AL) and spherical equivalent refraction (SER) were followed up at 3-, 6-, and 12-month. To evaluate the safety of RLRLT, at 6 and 12 months in the RLRL group, multifocal electroretinography (mfERG) and contrast sensitivity were recorded. Furthermore, optical coherence tomography was used to measure the relative reflectance of the ellipsoid zone (rEZR), photoreceptor outer segment (rPOSR), and retinal pigment epithelium (rRPER).

RESULTS

A total of 108 children completed the trial (55 in the RLRL group and 53 in the control group). After 3, 6, and 12 months, AL was shorter and SER less myopic in the RLRL group than in the control group. Regarding the safety of the RLRLT, the response density and amplitude of the P1 wave of the first ring of the mfERG increased significantly at 6 months (P = 0.001 and P = 0.017, respectively). At 6 and 12 months, contrast sensitivity at the high spatial frequency increased. Moreover, the rEZR increased significantly at 6 months (P = 0.029), the rPOSR increased significantly at 6 and 12 months (both P < 0.001), and the increase in rPOSR was greater with greater AL regression.

CONCLUSIONS

Based on retinal function and structure follow-up, RLRLT was safe within 12 months. However, rEZR and rPOSR increased, the effects of this phenomenon requires further observation.

Contrast sensitivity function under three light conditions in patients with type 1 diabetes mellitus without retinopathy: a cross-sectional, case-control study

PURPOSE

To determine whether patients with type 1 diabetes mellitus (T1DM), without any sign of diabetic retinopathy, have any alteration in Contrast Sensitivity Function (CSF), in relation to patients without this disease, and whether CSF assessment in three different light conditions can be an effective test in the early detection of diabetic retinopathy.

METHODS

A prospective, cross-sectional, case-control study was preformed including 80 patients (40 with T1DM without diabetic retinopathy and 40 controls) between 11 and 47 years old. CSF was assessed at four spatial frequencies (3, 6, 12 and 18 cycles/degree) using the CSV-1000E test, under three light conditions: high (550 lx), medium (200 lx) and low (< 2 lx).

RESULTS

A lower CSF in the T1DM group was found at the three light conditions studied. The most spatial frequency affected was 18 cpd, 0.08 log units (p = 0.048) in high, 0.10 log units (p = 0.010) in medium (p = 0.010) and 0.16 log units (p < 0.001) in low-light conditions in mean CS values. The least spatial frequency affected was 3 cpd (p > 0.05 in all three light conditions).

CONCLUSION

Patients with T1DM, without diabetic retinopathy, presented a loss of CS to sine-wave gratings, with respect to people with the same characteristics without the disease, mainly at medium and high frequencies, and in medium and low-light conditions.

Relationship Between Glycosylated Hemoglobin Levels and Contrast Sensitivity in People with Type 2 Diabetes Mellitus Without Diabetic Retinopathy

Objectives

This study aimed to investigate the relationship between glycosylated hemoglobin (HbA1c) value and contrast sensitivity (CS) in people with Type 2 diabetes mellitus (T2DM) and no diabetic retinopathy (DR) changes.

Materials and Methods

This cross-sectional study was conducted in the endocrinology department of a tertiary hospital and included 120 participants aged 30-40 years with T2DM without DR and with visual acuity of 6/6 in both eyes. Lea CS charts with one symbol size (10M) were used to measure CS. The relationship between HbA1c value and CS was calculated using linear regression analysis.

Results

Of 120 participants with T2DM without DR, 83 (69.2%) were female. Sixty-four participants (53.3%) were in the 36-40 years age group. Mean known duration of diabetes was 3.3±1.65 years. Mean HbA1c value was 10.46±1.48%, with three-fourths of participants having an HbA1c value greater than 8%. Mean CS measured at distances of 1 meter, 2 meters, 3 meters and 4 meters were 164.75±21.12, 122.0±45.08, 93.0±45.37, and 58.67±20.04, respectively. Most participants (n=113, 94.2%) had normal CS (170 at 0.6% contrast) tested at 1 meter. More than half (53.3%) of the participants had reduced CS (40 at 2.5% contrast) at 4 meters. CS measured at 3 meters showed a strong negative correlation with duration of diabetes (r=-0.855, p<0.001; R²=0.731) and HbA1c values (r=-0.865; p<0.001; R²=0.747).

Conclusion

CS was inversely associated with diabetes duration and HbA1c values in people with T2DM before any defect in visual acuity or clinical evidence of DR.

Contrast Sensitivity Assessment in Early Diagnosis of Diabetic Retinopathy: A Systematic Review

INTRODUCTION

The purpose of this systematic review was to study whether contrast sensitivity assessment in people with diabetes could be a reliable test in early detection of diabetic retinopathy. A systematic search based on population, intervention, comparison, and outcome strategy was performed.

METHODS

PubMed, Scopus, and Web of Science were searched for English articles of human patients with type 1 and type 2 diabetes and contrast sensitivity measurements as domain studied.

RESULTS

Twentyone comparative cross-sectional studies were included. All of them showed significant loss of contrast sensitivity in people with diabetes and diabetic retinopathy regarding control patients of the same age, regardless of the method used. However, those without diabetic retinopathy, involve a loss of contrast sensitivity, although not always significant.

CONCLUSION

Changes in contrast sensitivity suggest that there is damage to the retina prior to the vascular ones and that they could be detected by this test.

New Evidence of Central Nervous System Damage in Diabetes: Impairment of Fine Visual Discrimination

Diabetes can damage both the peripheral sensory organs, causing retinopathy, and the central visual system, leading to contrast sensitivity and impaired color vision in patients without retinopathy. Orientation discrimination is important for shape recognition by the visual system. Our psychophysical findings in this study show diminished orientation discrimination in patients with diabetes without retinopathy. To reveal the underlying mechanism, we established a diabetic mouse model and recorded in vivo electrophysiological data in the dorsal lateral geniculate nucleus (dLGN) and primary visual cortex (V1). Reduced orientation selectivity was observed in both individual and populations of neurons in V1 and dLGN, which increased in severity with disease duration. This diabetes-associated neuronal dysfunction appeared earlier in the V1 than dLGN. Additionally, neuronal activity and signal-to-noise ratio are reduced in V1 neurons of diabetic mice, leading to a decreased capacity for information processing by V1 neurons. Notably, the V1 in diabetic mice exhibits reduced excitatory neuronal activity and lower levels of phosphorylated mammalian target of rapamycin (mTOR). Our findings show that altered responses of both populations of and single V1 neurons may impair fine vision, thus expanding our understanding of the underlying causes of diabetes-related impairment of the central nervous system.

Electroretinography and contrast sensitivity, complementary translational biomarkers of sensory deficits in the visual system of individuals with fragile X syndrome

BACKGROUND

Disturbances in sensory function are an important clinical feature of neurodevelopmental disorders such as fragile X syndrome (FXS). Evidence also directly connects sensory abnormalities with the clinical expression of behavioral impairments in individuals with FXS; thus, positioning sensory function as a potential clinical target for the development of new therapeutics. Using electroretinography (ERG) and contrast sensitivity (CS), we previously reported the presence of sensory deficits in the visual system of the Fmr1-/y genetic mouse model of FXS. The goals of the current study were two-folds: (1) to assess the feasibility of measuring ERG and CS as a biomarker of sensory deficits in individuals with FXS, and (2) to investigate whether the deficits revealed by ERG and CS in Fmr1-/y mice translate to humans with FXS.

METHODS

Both ERG and CS were measured in a cohort of male individuals with FXS (n = 20, 18-45 years) and age-matched healthy controls (n = 20, 18-45 years). Under light-adapted conditions, and using both single flash and flicker (repeated train of flashes) stimulation protocols, retinal function was recorded from individual subjects using a portable, handheld, full-field flash ERG device (RETeval®, LKC Technologies Inc., Gaithersburg, MD, USA). CS was assessed in each subject using the LEA SYMBOLS® low-contrast test (Good-Lite, Elgin, IL, USA).

RESULTS

Data recording was successfully completed for ERG and assessment of CS in most individuals from both cohorts demonstrating the feasibility of these methods for use in the FXS population. Similar to previously reported findings from the Fmr1-/y genetic mouse model, individuals with FXS were found to exhibit reduced b-wave and flicker amplitude in ERG and an impaired ability to discriminate contrasts compared to healthy controls.

CONCLUSIONS

This study demonstrates the feasibility of using ERG and CS for assessing visual deficits in FXS and establishes the translational validity of the Fmr1-/y mice phenotype to individuals with FXS. By including electrophysiological and functional readouts, the results of this study suggest the utility of both ERG and CS (ERG-CS) as complementary translational biomarkers for characterizing sensory abnormalities found in FXS, with potential applications to the clinical development of novel therapeutics that target sensory function abnormalities to treat core symptomatology in FXS.

TRIAL REGISTRATION

ID-RCB number 2019-A01015-52 registered on the 17 May 2019.

Surgical Outcomes of Contrast Sensitivity and Visual Acuity in Uveitis-Associated Cataract

Purpose

To evaluate the pre- and post-operative outcomes of phacoemulsification in patients with uveitis-associated cataract in remission, such as conventional visual acuity (VA), photopic and mesopic contrast visual acuity (CVA), and flares in the anterior chamber objectively assessed as intraocular inflammation.

Patients and Methods

This prospective study included 26 eyes of 19 patients with uveitis and 45 eyes of 26 controls who underwent cataract surgery at the Kyushu University Hospital and Kyushu Medical Center in Fukuoka, Japan, from October 2016 to December 2018. Conventional VA and flare values in the anterior chamber were evaluated preoperatively and 1 and 3 months postoperatively. Photopic and mesopic CVAs were assessed preoperatively and 3 months postoperatively.

Results

The best-corrected VA (BCVA) was improved significantly from baseline to 1 and 3 months postoperatively in both groups (P < 0.01 in both groups). The mean preoperative 100% and 10% CVAs under the photopic condition were significantly lower in the uveitis group than in the control group (P < 0.05 for both CVA), whereas the mean preoperative 100% CVA under the mesopic condition was comparable between the two groups. Although the mean preoperative 100% and 10% CVAs improved significantly from baseline under both photopic and mesopic conditions in both groups (P < 0.01 in both groups), the postoperative contrast sensitivities under both photopic and mesopic conditions remained lower in the uveitis group than in the control group (P < 0.01 for both conditions). The postoperative complications included recurrence of active inflammation in five eyes and cystoid macular edema in one eye and were managed by topical steroid therapy alone.

Conclusion

Cataract surgery for uveitis-associated cataracts during remission is well tolerated. However, the present results suggest that amelioration of hemeralopia and/or nyctalopia is not as good as expected after cataract surgery in patients with uveitis.

THE LOSS OF INFRARED LIGHT SENSITIVITY OF PHOTORECEPTOR CELLS MEASURED WITH TWO-PHOTON EXCITATION AS AN INDICATOR OF DIABETIC RETINOPATHY: A Pilot Study

PURPOSE

Human photoreceptors are sensitive to infrared light (IR). This sensitivity can be used as a novel indicator of retinal function. Diabetic retinopathy patients were assessed using in vivo two-photon excitation and compared their scotopic IR threshold with that of healthy patients.

METHODS

Sixty-two participants, 28 healthy and 34 with diabetic retinopathy, underwent a comprehensive eye examination, where visual acuity and contrast sensitivity were assessed. Infrared thresholds were measured in the fovea and parafovea following 30-minute dark adaptation. A two-photon excitation device was used with integrated pulsed laser light (1,045 nm) for sensitivity testing and scanning laser ophthalmoscopy for fundus imaging.

RESULTS

The mean Snellen visual acuity of diabetic patients (6/7.7) was worse than that of the healthy patients (6/5.5), which was significantly different (P < 0.001). Disease patients had decreased contrast sensitivity, especially at 6 and 18 cycles/degree. The mean retinal sensitivity to IR light in eyes with diabetic retinopathy (11.6 ± 2.0 dB) was significantly (P < 0.001) lower than that in normal eyes (15.5 ± 1.3 dB).

CONCLUSION

Compared with healthy control subjects, the IR light sensitivity of diabetic patients was significantly impaired. Two-photon measurements can be used in the assessment of retinal disease, but further studies are needed to validate IR light stimulation in various stages of diabetic retinopathy.

The relation between the severity of reading disorder and visual functions among children with dyslexia

PURPOSE:

The purpose of the study was to investigate the relation between the severity of reading disorder and visual functions among children with dyslexia.

MATERIALS AND METHODS:

The present study included 32 dyslexic children selected from two centers for learning disabilities in Mashhad, Iran. Dyslexics were then classified as mild, moderate, and severe based on an instrument used to determine the severity of their reading disorder. Complete optometric examinations to measure visual acuity, refractive errors, latent and manifest deviations, stereoacuity, and amplitude of accommodation were performed for all participants. The correlation between visual functions among dyslexics and their reading disorder severity was investigated.

RESULTS:

The mean age of the participants in this study was 8.1 ± 0.8 years. Among participants, 40.6%, 31.3%, and 28.1% presented with severe, moderate, and mild levels of reading difficulties, respectively. Only exophoria significantly correlated with the severity of reading disorders. No significant correlation was found between other visual functions and the severity of reading disorders in dyslexic children.

CONCLUSION:

We found that higher exophoria at near has a significant correlation with the severity of dyslexia. A complete and detailed eye examination of patients with dyslexia and correcting their visual impairments might be helpful.

Visual contrast sensitivity could be an early marker of diabetic retinopathy

The present study aimed to explore the early predictive marker of diabetic retinopathy (DR) and to elucidate the associated demographic, metabolic, and ocular factors. We enrolled 43 type 2 diabetic subjects with mild non-proliferative retinopathy (MNPDR), 30 diabetic subjects with no retinopathy (DNR), and 35 healthy controls (HC). The study groups showed no significant alteration in central macular thickness (CMT) and visual acuity (VA). The contrast sensitivity (CS) score was found to be significantly lower among DNR and MNPDR subjects compared to HCs (p < 0.0001). Between MNPDR and DNR subjects, the CS score was significantly lower in the former (p = 0.0036). CS score discriminated DNR subjects from HC, with 74% accuracy for the optimal threshold 0.71. The associated area under the ROC curve (AUC) is 0.82 (p < 0.0001) while the discrimination rule has 66% sensitivity and 80% specificity. The CS score also discriminated MNPDR subjects from DNR with 64% accuracy for the optimal threshold 0.53. The associated AUC is 0.65 (p < 0.023) and the rule has 86% sensitivity and 33% specificity. According to best subset regression analysis, not only glycaemic parameters but also lipid parameters [low-density lipoprotein cholesterol (LDL-C) (p = 0.045) and triglycerides (TG) (p = 0.0005)] were found to be significant predictors of CS. CMT (p = 0.058) was another marginally significant predictor of CS. CS may be used as an early predictive marker for DR. So, not only hyperglycemia, but also hyperlipidemia seems to significantly affect retinal CS function in diabetes.

Contrast-Sensitivity Function and Photo Stress-Recovery Time in Prediabetes

PURPOSE

The purpose of this study was to assess contrast sensitivity and macular function test in prediabetes.

METHODS

Participants aged 25-45 years with or without diabetes were enrolled and classified as normal, prediabetic, and diabetic based on their HbA1C values. They underwent a comprehensive eye examination, and those with diabetic retinopathy, cataract, glaucoma, and high myopia were excluded. Participants with best-corrected visual acuity of 0 logMAR were included. Contrast-sensitivity function (CSF) was measured using a Pelli-Robson chart, and photo stress-recovery time (PSRT) assessed using direct ophthalmoscopy for the 70 eligible participants. Mean values were compared among the three groups.

DESIGN

This was a cross-sectional observational study.

RESULTS

In the 70 participants, mean CSF was 1.71±0.10, 1.64±0.11, and 1.61±0.08 log units in the normal, prediabetic, and diabetic groups, respectively (p<0.001). Similarly, PSRT was found to be 35.80 seconds, 41.63 seconds, and 47.77 seconds in the normal, prediabetic, and diabetic groups, respectively (p<0.001).

CONCLUSION

The data suggested that reduced CSF and delayed PSRT seen in subjects with prediabetes could give valuable clinical insight into early changes before diabetes and microvascular damage is incurred. A future study with a larger sample could help substantiate the results.

The effects of early diabetes on inner retinal neurons

Diabetic retinopathy is now well understood as a neurovascular disease. Significant deficits early in diabetes are found in the inner retina that consists of bipolar cells that receive inputs from rod and cone photoreceptors, ganglion cells that receive inputs from bipolar cells, and amacrine cells that modulate these connections. These functional deficits can be measured in vivo in diabetic humans and animal models using the electroretinogram (ERG) and behavioral visual testing. Early effects of diabetes on both the human and animal model ERGs are changes to the oscillatory potentials that suggest dysfunctional communication between amacrine cells and bipolar cells as well as ERG measures that suggest ganglion cell dysfunction. These are coupled with changes in contrast sensitivity that suggest inner retinal changes. Mechanistic in vitro neuronal studies have suggested that these inner retinal changes are due to decreased inhibition in the retina, potentially due to decreased gamma aminobutyric acid (GABA) release, increased glutamate release, and increased excitation of retinal ganglion cells. Inner retinal deficits in dopamine levels have also been observed that can be reversed to limit inner retinal damage. Inner retinal targets present a promising new avenue for therapies for early-stage diabetic eye disease.

Early diabetes impairs ON sustained ganglion cell light responses and adaptation without cell death or dopamine insensitivity

Retinal signaling under dark-adapted conditions is perturbed during early diabetes. Additionally, dopamine, the main neuromodulator of retinal light adaptation, is diminished in diabetic retinas. However, it is not known if this dopamine deficiency changes how the retina responds to increased light or dopamine. Here we determine whether light adaptation is impaired in the diabetic retina, and investigate potential mechanism(s) of impairment. Diabetes was induced in C57BL/6J male mice via 3 intraperitoneal injections of streptozotocin (75 mg/kg) and confirmed by blood glucose levels more than 200 mg/dL. After 6 weeks, whole-cell recordings of light-evoked and spontaneous inhibitory postsynaptic currents (IPSCs) or excitatory postsynaptic currents (EPSCs) were made from rod bipolar cells and ON sustained ganglion cells, respectively. Light responses were recorded before and after D1 receptor (D1R) activation (SKF-38393, 20 μM) or light adaptation (background of 950 photons·μm^-2 ·s^-1). Retinal whole mounts were stained for either tyrosine hydroxylase and activated caspase-3 or GAD65/67, GlyT1 and RBPMS and imaged. D1R activation and light adaptation both decreased inhibition, but the disinhibition was not different between control and diabetic rod bipolar cells. However, diabetic ganglion cell light-evoked EPSCs were increased in the dark and showed reduced light adaptation. No differences were found in light adaptation of spontaneous EPSC parameters, suggesting upstream changes. No changes in cell density were found for dopaminergic, glycinergic or GABAergic amacrine cells, or ganglion cells. Thus, in early diabetes, ON sustained ganglion cells receive excessive excitation under dark- and light-adapted conditions. Our results show that this is not attributable to loss in number or dopamine sensitivity of inhibitory amacrine cells or loss of dopaminergic amacrine cells.

REDD1 Activates a ROS-Generating Feedback Loop in the Retina of Diabetic Mice

Purpose

The present study was designed to evaluate the role of the stress response protein REDD1 in diabetes-induced oxidative stress and retinal pathology.

Methods

Wild-type and REDD1-deficient mice were administered streptozotocin to induce diabetes. Some mice received the antioxidant N-acetyl-l-cysteine (NAC). Visual function was assessed by virtual optometry. Retinas were analyzed by Western blotting. Reactive oxygen species (ROS) were assessed by 2,7-dichlorofluoroscein. Similar analyses were performed on R28 retinal cells in culture exposed to hyperglycemic conditions, NAC, and/or the exogenous ROS source hydrogen peroxide.

Results

In the retina of diabetic mice, REDD1 expression and ROS were increased. In cells in culture, hyperglycemic conditions enhanced REDD1 expression, ROS levels, and the mitochondrial membrane potential. However, similar effects were not observed in the retina of diabetic mice or cells lacking REDD1. In the retina of diabetic mice and cells exposed to hyperglycemic conditions, NAC normalized ROS and prevented an increase in REDD1 expression. Diabetic mice receiving NAC also exhibited improved contrast sensitivity as compared to diabetic controls. Hydrogen peroxide addition to culture medium increased REDD1 expression and attenuated Akt/GSK3 phosphorylation in a REDD1-dependent manner. In REDD1-deficient cells exposed to hyperglycemic conditions, expression of a dominant negative Akt or constitutively active GSK3 increased the mitochondrial membrane potential and promoted ROS.

Conclusions

The findings provide new insight into the mechanism whereby diabetes-induced hyperglycemia causes oxidative stress and visual dysfunction. Specifically, hyperglycemia-induced REDD1 activates a ROS-generating feedback loop that includes Akt/GSK3. Thus, therapeutic approaches targeting REDD1 expression and ROS may be beneficial for preventing diabetes-induced visual dysfunction.

Measurement of Contrast Sensitivity in Patients with Behçet's Disease without Ocular Involvement

Purpose

To evaluate contrast sensitivity in patients with Behçet's disease (BD) without ocular involvement.

Methods

The study group was composed of 47 BD patients (20 to 50 years of age) who did not have ocular involvement. The control group was composed of 47 normal volunteers who were similar to the study group in terms of age and gender. No participants in this study had any ocular or systemic pathologies except for BD. The contrast sensitivity measurements were performed using the Functional Acuity Contrast Test under photopic conditions, and the results were compared between the two groups.

Results

The mean age of the BD patients and control subjects was 34.5 ± 9.7 and 33.2 ± 7.6 years, respectively. The mean disease duration of the BD patients was 5.5 ± 6.4 years. There was a statistically significant decrease at five spatial frequencies (A, 1.5; B, 3; C, 6; D, 2; and E, 18 cycles per degree) in patients with BD compared with control subjects (p < 0.001, p = 0.004, p = 0.002, p < 0.001, and p = 0.001, respectively).

Conclusions

The contrast sensitivity of BD patients without ocular involvement was lower than that of the control group. Further studies seem mandatory to confirm our results.

Effect of Varying Levels of Glare on Contrast Sensitivity Measurements of Young Healthy Individuals Under Photopic and Mesopic Vision

Contrast sensitivity (CS), the ability to detect small spatial changes of luminance, is a fundamental aspect of vision. However, while visual acuity is commonly measured in eye clinics, CS is often not assessed. At issue is that tests of CS are not highly standardized in the field and that, in many cases, optotypes used are not sensitive enough to measure graduations of performance and visual abilities within the normal range. Here, in order to develop more sensitive measures of CS, we examined how CS is affected by different combinations of glare and ambient lighting in young healthy participants. We found that low levels of glare have a relatively small impact on vision under both photopic and mesopic conditions, while higher levels had significantly greater consequences on CS under mesopic conditions. Importantly, we found that the amount of glare induced by a standard built-in system (69 lux) was insufficient to induce CS reduction, but increasing to 125 lux with a custom system did cause a significant reduction and shift of CS in healthy individuals. This research provides important data that can help guide the use of CS measures that yield more sensitivity to characterize visual processing abilities in a variety of populations with ecological validity for non-ideal viewing conditions such as night time driving.

Evaluation of contrast sensitivity and other visual function outcomes in diabetic macular edema patients following treatment switch to aflibercept from ranibizumab

Purpose

This study aims to investigate changes in contrast sensitivity (CS), visual acuity (VA), central retinal thickness (CRT), and vision-related quality of life in subjects with recalcitrant diabetic macular edema switched from long-term ranibizumab treatment to aflibercept.

Patients and methods

In this prospective, investigator-masked, single-center study, 40 patients with persistent fluid, despite previous ranibizumab treatment, were switched to aflibercept with 5 consecutive monthly doses. The primary outcome was mean change from baseline to week 20 in Pelli–Robson CS. Secondary outcomes were mean change from baseline in best-corrected VA (BCVA), CRT, and National Eye Institute 25-Item Visual Function Questionnaire score.

Results

Fifty eyes (baseline VA >6/30) were evaluated. A median of 21.1±11.9 (range 5–55) ranibizumab injections were administered prior to initiation of aflibercept. Mean CS improved from 1.40±0.14 log units at baseline to 1.46±0.15 log units at week 20 (P<0.001). VA improved with mean logarithm of the minimum angle of resolution BCVA of 0.33±0.19 at baseline compared with logarithm of the minimum angle of resolution BCVA of 0.28±0.16 at week 20 (P=0.0016). Mean CRT decreased from 324±85 to 289±61 µm (P<0.001). Twenty-two (55%) patients experienced an overall improvement in National Eye Institute 25-Item Visual Function Questionnaire score. Interestingly, an association was found between changes in CS and change in CRT (r²=0.385, P<0.001) and between changes in BCVA and change in CRT (r²=0.092, P=0.032).

Conclusion

Switching from ranibizumab to aflibercept in patients with recalcitrant diabetic macular edema resulted in an improvement in all measured metrics, including CS, VA, and CRT. A majority of patients also indicated an improvement in vision-related quality of life. The finding of a stronger relationship between changes in CRT and CS compared with changes in CRT and BCVA suggests that the inclusion of CS as an endpoint may yield a more complete understanding of visual outcomes than that obtained by using VA alone.