Effect of Viewing Distance on Peripheral Refraction in myopes.

Abstract

Abstract: : Purpose:Previous studies have shown that myopic eyes are relatively more hyperopic in the periphery relative to the fovea than hyperopic eyes. We investigated the effect of changing the viewing distance on peripheral refraction in myopes and emmetropes. Methods:The PowerRefractor was used to measure peripheral refraction in a group of 10 myopes and 10 emmetropes. Measurements were taken at eccentricities of 0°, 10° and 20° nasal to the fovea and 10° and 20° temporal to the fovea at viewing distances of 2.5m and 40cm. Results:The results showed no significant difference in peripheral refraction between the two groups both at distance (p > 0.05) and near (p > 0.05). Refractive error changed significantly with eccentricity in both groups (p = 0.001). The temporal retina was found to be more astigmatic than the nasal retina at distance. For a viewing distance of 40cm, the nasal retina was found to be more astigmatic than the temporal retina. Conclusions:Myopes showed no significant difference in peripheral refraction from emmetropes for both distance and near targets. The shift in increased astigmatism from the temporal retina to the nasal retina at near might be explained by changes in intraocular lens topography with accommodation.

Keywords: myopia • refraction • visual development