Diabetic macular edema assessed with optical coherence tomography and stereo fundus photography

To compare retinal thickening in diabetic macular edema assessed subjectively by evaluation of stereo fundus photographs with that assessed objectively by optical coherence tomography (OCT).

Forty-degree stereo fundus photographs of the macular field and OCT scans in 84 eyes of 47 patients with diabetes were compared in terms of both location and area of retinal thickening. Six radiating 6-mm OCT scans at intervals of 30 degrees were obtained, and the retinal thickness was compared with the mean retinal thickness +/- 2 SD of healthy control subjects (33 eyes). Subsequently, retinal thickness was mapped topographically and the subjectively assessed retinal thickening map was overlaid. The degree of agreement on location was evaluated as retinal thickening present or absent in nine subfields of the fundus. Area of retinal thickening was divided into four categories: no retinal thickening, less than 1 disc area (DA), less than 2 DAs, or less than 3 DAs, expressed as the kappa statistic.

Exact agreement on location was found in 676 of 756 (84 x 9) observations (89.4%; kappa = 0.69; 95% confidence interval [CI]: 0.63-0.75). Two eyes in which both methods assessed the same amount of retinal thickening showed no agreement on location. These eyes were compared only in terms of location. Exact agreement on area was found in 69 (84.1%) of 82 eyes. Weighted kappa (kappa(w)) = 0.79; 95% CI: 0.76-0.82).

The degree of agreement between subjectively and objectively assessed retinal thickening was very good, implying that changes in diabetic macular edema can be accurately and prospectively measured with OCT.