Comparison of macular retinal sensitivity and its contribution to the foveal sensitivity between diabetic and non-diabetic patients with normal visual acuity.

PURPOSE: To compare the retinal sensitivity and evaluate its contribution to the foveal sensitivity in patients with and without diabetes who maintain normal visual acuity.

METHODS: Observational, descriptive, cross-sectional and prospective study in 20 subjects without diabetes (group 1) and 23 with type 2 diabetes mellitus (group 2) that had no ocular abnormalities. Retinal sensitivity was measured with the macular threshold test by the Humphrey's computerized perimeter. The mean sensitivity in each of the 16 points and the foveal sensitivity were compared between groups using the Mann-Whitney's U test; the correlation between retinal sensitivity and foveal sensitivity was analyzed by the Spearman's test and the contribution of each point to the foveal sensitivity was identified by multiple regression.

RESULTS: Sixty eyes were evaluated, 30 in group 1 and 30 in group 2; the mean foveal sensitivity was 34.77±0.5dB in group 1 and 32.87±0.6 in group 2. The highest sensitivity of the temporal visual field had an inferior paracentral location (point 3) in both groups. In the linear regression analysis, points which contributed to the foveal sensitivity were 1 in group 1 and points 7 and 15 in group 2.

CONCLUSIONS: Subjects without diabetes have a significantly higher sensitivity in the temporal retina compared with those with diabetes; points with highest mean retinal sensitivity do not correspond to the central four. The reduced sensitivity in point 1 decreases the mean foveal sensitivity in subjects with diabetes, because this variable correlates with lower perimetry points.