Contrast sensitivity loss is coupled with capillary dropout in patients with diabetes

Purpose. To assess the relationship of foveal microcirculation to contrast sensitivity function in early diabetes mellitus. Methods. Twenty patients with diabetes with visual acuity of 20/25 or better without clinically significant macular edema were evaluated. Measurements of contrast sensitivity at four spatial frequencies (3, 6, 12, and 18 cycles/degree [c/deg]), macular capillary blood velocity (CBV), capillary density (PIA: perifoveal intercapillary area), foveal avascular zone (FAZ), and microaneurysm count were performed. Contrast sensitivity data collected from age-matched normal subjects and previously published normal angiographic data were used for comparison with our cohort with diabetes. Results. The CBV was significantly reduced (P < 0.0001) and PIA and FAZ were significantly enlarged (P < 0.0001) when compared with healthy subjects: Contrast sensitivity was significantly lower in the group with diabetes at 6 (P = 0.01) and 12 (P = 0.002) c/deg as compared with healthy control values. FAZ and PIA correlated significantly (FAZ; r = -0.60, P = 0.005; PIA; r = -0.54, P = 0.02) with contrast sensitivity at 12 c/deg: Conclusions. The alterations of the perifoveal network are related to selective disturbances of central visual function as measured by contrast sensitivity. In patients with diabetes measurement of contrast sensitivity may provide a clinical adjunct in further identifying early ischemic diabetic maculopathy.