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

Abstract

ObjectiveTo 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 methodsIn 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.ResultsCS 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).ConclusionsOur 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.

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

“…A further experiment (Experiment 3), aimed at measuring a range of illumination intensities in mesopic light condition confirmed results obtained in Experiment 2 and showed that values above 125 lux did induce a significant decrease of the CSF. Taken together, the present results suggest that, while glare-induced reduction of the CSF can be achieved with currently available systems in clinical populations, i.e., astigmatism patients who underwent LASIK surgery ( Safi et al, 2017 ), in order to successfully reduce the CSF in young healthy individuals it is necessary to use a luminance level that the currently available standard CS tests do not reach (125 lux).…”

“…Nonetheless, future studies should also assess whether the photopic CSF can be similarly affected by extremely high levels of glare in young healthy individuals. This would provide an additional valuable piece of information since Safi et al (2017) showed that comparing CS measured in different light conditions produces a more accurate classification of diabetic patients with no retinopathy from normal sighted individuals respect to the CS measured under a single light condition; similarly, comparing mesopic and photopic CS with glare might reveal subtle differences that might be lost in a single light condition test.…”

“…While the CSF is generally measured in a low light environment, changing ambient lighting conditions can affect CS measurements in distinct and clinically relevant ways ( Rabin, 1994 ; Pesudovs et al, 2004 ). Recently Safi et al (2017) reported that the observed reduction of CS in diabetic patients depended on the illumination conditions of the testing stimulus; in particular, CS was impaired in response to spatial frequencies above 3 cycles per degree in photopic condition, while CS was reduced over the entire spatial frequency range in mesopic condition. Importantly, Safi et al (2017) demonstrated better classification of diabetic patients from controls using a logistic model that incorporated measurements from two different light conditions compared to using a single CS measurement.…”

Visual contrast sensitivity could be an early marker of diabetic retinopathy

“…On the contrary, a group of vision researchers have shown that CS, a measure of the ability of an individual to discriminate among different shades of gray, is a more sensitive tool to detect the early retinal changes and distinguish different diabetic subgroups than VA ( Dosso et al., 1998 ; Abrishami et al., 2007 ; McAnany et al., 2019 ). A study by Safi et al. (2017) showed that patients with diabetes (without any clinical signs of retinopathy) exhibited a uniform loss in CS at different special frequencies like 3, 6, 12, and 18 cycles/degree.…”

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

“…24 , 25 Studies have shown that even in diabetic patients with good VA, CS could be impaired. 26 – 28 CS is thus an important outcome measure and could be considered as an adjunct to standard VA testing for a more complete assessment of visual function in DME patients. The CS test has been proven useful for diagnosing early and advanced DR. 24 , 26 , 29 It has also grown in popularity as a clinical tool for evaluating the impact of therapy since potential treatment response may not be completely characterized by VA measurement alone.…”