Abstract
Purpose: :
To describe the intersession repeatability of visual function tests in patients with mild diabetic retinopathy.
Methods: :
Visual function tests were prospectively done on 35 eyes of 35 patients with mild diabetic retinopathy with no OCT evidence of maculopathy. Best corrected visual acuity (ETDRS letters), colour vision thresholds on Chroma test, contrast sensitivity obtained by Pelli-Robson charts and mean retinal sensitivity obtained by MP1, Nidek were tested twice at baseline, and then at 3rd and 6th month visits, using a standardized protocols. The difference between means across the three sessions was analyzed by using the mixed within-subject analysis of variance (ANOVA) method in functions with normal distribution while Friedman test was used for the others. The Bland and Altman plots were done for all visual functions and OCT measurements and the coefficient of repeatability (CR) calculated. The difference between two measurements for the same subject is expected to be less than the CR for 95% of pairs of observations.
Results: :
The coefficient of repeatability for ETDRS letters was 11.76 letters, protan threshold was 3.67 db, tritan threshold 5.11 db, contrast sensitivity 6.7 letters, mean retinal sensitivity was 3.29 db and the central 1-mm macular subfield was 16.33 µm.
Conclusions: :
Although no clinical evidence of disease progression was noted in any of these patients in this time period, the intersession visual function measurements are subject to variability in patients with mild DR. The variability may be due to both measurement and disease-related factors.
Keywords: diabetic retinopathy • visual acuity • contrast sensitivity