Optical Coherence Tomography for Retinal Thickness Measurement in Diabetic Patients Without Clinically Significant Macular Edema

Abstract

To evaluate the potential of optical coherence tomography (OCT) as a screening method for retinal thickness measurements in diabetic patients. We used a previously described pattern of six 5 mm OCT scans through the center of fixation in 45 diabetic patients without clinically significant macular edema: 22 patients (group 1) had no diabetic retinopathy (ETDRS classification); 18 (group 2) had nonproliferative retinopathy; 5 patients with peripheral neovascularization did not enter statistical analysis; 25 normal healthy subjects were used as a control group. Retinal thickness was measured at five locations in each scan: in the fovea, at the foveal rim, and outside the macula. Measurements were identified in nonaligned images and taken from raw data A-scans. Locations were grouped into hemispheres, quadrants and rings, and mean values tested for statistically significant differences using Mann-Whitney U-Wilcoxon rank sum W test. Differences in retinal thickness were found to be significant in the macula (controls vs group 2 P = 0.0266), at the foveal rim (controls vs group 1 and 2: P = 0.0386 and P = 0.0193), in the nasal and superior hemisphere (controls vs group 2: P = 0.0251 and P = 0.0187), and in the superior nasal quadrant (controls vs group 1 and group 1 vs group 2: P = 0.0022 and P = 0.0462). Significant differences of retinal thickness between patients with diabetic retinopathy and normals can be detected by OCT even in the absence of clinically significant macular edema. Significant differences between diabetic patients with and without retinopathy are most likely to be found in the superior nasal quadrant.