Abstract
Abstract: :
Purpose:To test the prediction that sampling–limited acuity is reduced in myopes. Methods:Resolution acuity for sinusoidal gratings in the fovea and 5 peripheral locations was measured in 60 myopic subjects having a wide range of refractive errors. Control experiments using a detection paradigm to evoke spatial aliasing ensured that acuity was sampling limited. Retinal spatial frequencies of the grating stimulus were computed assuming Knapps’ Law, which states that retinal image size (in mm) is independent of refractive error when axial myopia is corrected by a spectacle lens located in the anterior focal plane of the eye (Bennett & Rabbetts, 1998). Results:At all six eccentricities, resolution acuity tended to be lower in subjects with larger amounts of myopia. Regression of the population data indicated that about 16D of refractive error reduces resolution acuity by the factor 2 relative to the emmetropic eye. Several patients also demonstrated sampling–limited performance in the fovea, which indicates that optical filtering by the eye’s optical system failed to protect the fovea from aliasing artifacts of neural undersampling in these myopic eyes. Conclusions:Our results indicate that stretching of the retina is a primary cause of reduced spatial resolution of the peripheral field, and occasionally of the fovea, of myopic eyes. Stretching appears to be uniform over the central ± 15 degrees of visual field.