Optical coherence tomography for the detection of early macular edema in diabetic patients with retinopathy.

AIM: To compare the retinal thickness measurements with spectral-domain optical coherence tomography (OCT) in healthy subjects with those of type 2 diabetes patients with or without diabetic retinopathy (DR) and with no clinical evidence of diabetic macular edema (DME).

PATIENTS AND METHODS: The present prospective study included 29 diabetic patients (57 eyes) with no DR (group 1), 32 diabetic patients (63 eyes) with DR (group 2) and 25 healthy volunteers (39 eyes, control group). Eyes showing macular edema on slit-lamp biomicroscopy or leakage on fluorescein angiography were not included in the study. The mean retinal thickness at the central fixation point (CFP) and the 9 ETDRS macular regions were compared in subgroups of healthy volunteers by age, sex and right or left eye. These mean retinal thickness values were also compared in the control group, group 1 and group 2. Early DME was diagnosed with OCT if it exceeded the mean thickness +2.SD (standard deviation) in healthy subjects.

RESULTS: Mean retinal thickness at the CFP and fovea in healthy eyes was 176 +/- 16.8 microm and 198.3 +/- 21.4 microm, respectively. It was significantly greater in men than in women (p < 0.05), decreased with age and showed no statistically significant difference between right and left eyes. Differences in retinal thickness were found to be significant for the CFP and all ETDRS regions (controls vs. group 1 and controls vs. group 2) and for the CFP, fovea, superior inner, temporal inner and nasal inner ETDRS regions (group 1 vs. group 2, group 2 having greater thickness). Early DME was diagnosed at retinal thickness exceeding 209.6 microm at the CFP and 241.1 microm at the fovea in 13 eyes of diabetic patients from group 2. Twelve eyes with early DME had mild non-proliferative DR and one--moderate non-proliferative DR.

CONCLUSION: In the present study, mean retinal thickness was greater in diabetic patients (with and without DR) than in healthy subjects. Patients with DR had thicker retinas than patients without DR. Spectral-domain OCT seemed to be useful for the detection of early DME in patients with retinopathy and no clinical evidence of macular edema. Patients with early DME should have a closer follow-up