Decreased OCT measured central retinal thickness in patients with and without minimal diabetic retinopathy

Purpose: To evaluate OCT measured central retinal thickness (RT) in diabetes mellitus (DM) patients, with or without minimal diabetic retinopathy (DR). Methods: DM patients with or without minimal DR on biomicroscopy, were included and underwent a full ophthalmologic examination, (redfree) fundus photography and OCT scanning of the macula using StratusOCT (Zeiss). Mean RT measurements of the fovea (A1), pericentral ring (A2-A5) and the peripheral ring (A6-A9) in the patients were compared with RT measurements in normal, sex and age-matched subjects. Results: One hundred DM patients were included in this study of which 50 type 1 and 50 type 2. Fundus photography showed either no abnormalities or only few microaneurysms in the posterior pole. The mean pericentral RT was significantly decreased in DM patients with and without minimal DR compared with the normal controls (n=100). The predicted value of the mean pericentral RT calculated with a regression model, based on the normal subjects, was not significantly different from the truly measured mean pericentral RT. Conclusions: In contrast with previous studies, we found that the pericentral RT in DM patients seems to be decreased compared to healthy subjects. This could be explained by the loss of intraretinal neurons in the earliest stage of DR. The use of a regression model suggests this neural tissue loss is not restricted to the pericentral region.