Contrast Sensitivity and Inner Retinal Layer Thickness Analysis of Type 2 Diabetic Patients Without Retinopathy

ABSTRACT

Purpose@#To compare the contrast sensitivities of type 2 diabetic patients without retinopathy and healthy subjects, and to assess the risk factors associated with a change in contrast sensitivity in diabetes. @*Methods@#A total of 75 (diabetic patients without retinopathy) and 41 (healthy subjects) eyes were reviewed from the medical records. The threshold of contrast sensitivity was measured at 6.3°, 4.0°, 2.5°, 1.6°, 1.0°, and 0.64° under scotopic and photopic states. Optical coherence tomography (OCT) imaging was used to measure the retinal nerve fiber layer (RNFL) thickness and ganglion cell-inner plexiform layer (GC-IPL) thickness in diabetic patients. @*Results@#Diabetic patients showed a lower threshold of contrast sensitivity at all degree measures than did the controls under both scotopic and photopic states. In subgroup analyses, diabetic patients with abnormal contrast sensitivity showed a longer duration of diabetes, decreased total retinal thickness, and decreased average GC-IPL, superior RNFL, superior GC-IPL, and temporal GC-IPL thicknesses. Multivariate logistic regression analyses showed that the duration of diabetes and total retinal thickness were significant predictive factors of decreased contrast sensitivity (odds ratio = 1.117 and 0.942, respectively). @*Conclusions@#As the duration of diabetes increased, the contrast sensitivity decreased in type 2 diabetic patients. Neuroretinal degeneration changes both the inner retinal thickness and total retinal thickness and affects contrast sensitivity. Therefore, for longer-term diabetic patients, it is necessary to consider the changes in contrast sensitivity and retinal thickness on OCT evaluation, even if the patient presents with normal fundus findings.