Comparison of objective retinal thickness analysis and subjective stereo fundus photography in diabetic macular edema

Abstract

PURPOSE. To compare assessment of retinal thickening by stereo fundus photographs and by Retinal Thickness Analysis (RTA). METHODS. Forty-degree stereo fundus photographs of the macular field, and RTA scans in 99 eyes of 53 diabetic patients were compared in both location and area of retinal thickening. The deviation in retinal thickness on RTA from the mean retinal thickness ±2 SD in healthy controls was mapped in a spread-sheet and printed, assuming the same size as the grid with the subjectively assessed retinal thickening. Location was evaluated as retinal thickening being present or absent in nine subfields. Area was one of four categories: No retinal thickening, <1 disc area (DA), <2 DA, or <3 DA. Statistics: κ-statistic. RESULTS. Exact agreement on location was found in 632 of 891 observations (70.9%). κ = 0.17 (95% CI: 0.08-0.25). Pooling observations for subfields 2 to 5 (inner circle), and 6 to 9 (outer circle) showed exact agreement = 75.8% and κ = 0.10 (95% CI: -0.06-0.25) and exact agreement = 65.2% and κ = 0.24 (95% CI: 0.13-0.34), respectively. Twelve eyes, in which both methods assessed the same amount of retinal thickening, showed no agreement on location, and were compared only on location of retinal thickening. Exact agreement on area was found in 44 of 87 (50.6%) eyes. Weighted Kappa = 0.34 (95% CI: 0.23-0.45). CONCLUSIONS. The degree of agreement between subjectively (with stereo fundus photographs) and objectively (with RTA) assessed location and area of retinal thickening was poor, and fair, respectively.