Macular thickness measured by optical coherence tomography (OCT) in diabetic patients

1) To compare macular thickness (MT) by optical coherence tomography (OCT) in diabetics and controls; 2) to assess the relationship between MT and stage of diabetic retinopathy (DR) and macular edema (ME); 3) to quantify MT changes after laser treatment for ME.

One-hundred and thirty-seven patients with diabetes mellitus (216 eyes) were admitted to the study and examined by stereo-color fundus photos, retinal fluorangiography and OCT. DR was classified as: 1) no DR (46 eyes: 21.3%); 2) background DR (66 eyes: 30.6%); 3) pre-proliferative DR (50 eyes: 23.1%); 4) proliferative DR (54 eyes: 25%). The study group was then divided into three ME groups: 1) no edema (65 eyes: 30.1%); 2) not clinically significant ME (no CSME) (45 eyes: 20.8%); 3) clinically significant macular edema (CSME) (106 eyes: 49.1%). Three-month follow-up tomograms were taken to evaluate eyes laser-treated only for ME. The control group consisted of 50 eyes of 50 non-diabetic, age- and sex-matched subjects.

MT was 369.3 +/- 163.2 microm in diabetics and 161.9 +/- 12.9 microm in controls (p < 0.001). In the four DR groups it was: 1) 211.0 +/- 37.6 microm; 2) 370.8 +/- 159.6 microm; 3) 419.1 +/- 138.2 microm; 4) 456.1 +/- 162.0 microm (p<0.001). In the three ME groups, MT was: 1)227.8 +/- 53.4 microm; 2) 321.8 +/- 124.2 microm; 3) 476.2 +/-146.6 microm (p < 0.001). In the 52 eyes treated with laser photocoagulation of the posterior pole only and with a follow-up > 3 months, MT before and after treatment was 468.2 +/- 83. 17 microm and 372.1 +/- 120.63 microm.

MT was greater in diabetics than controls and tended to increase with DR and ME severity. OCT is a sensitive technique for detecting early diabetic macular abnormalities and quantifying their reduction after laser treatment.