Psychophysical Measurement of Retinal Sampling Density in Age-Related Maculopathy(ARM)

Abstract

Abstract: : Purpose To explore the relationship between novel psychophysical measures of retinal sampling density and ARM status. Methods 46 subjects aged between 51-87 yrs, had LogMAR visual acuity, contrast sensitivity and color vision measured in both eyes after standardised refraction. One eye of each subject was then selected to perform different psychophysical acuity tests. In subjects with unilateral AMD this was the unaffected eye. In all others, including those with ARM, the eye with better acuity was selected. If acuity was equal in both eyes, one eye was randomly assigned study eye status. Foveal photopic and scotopic interferometry was performed using a Lotmar visometer. Subjects also underwent achromatic and short wavelength resolution acuity at 6 degrees eccentricity in 4 oblique meridians. Severity of ARM was graded and staged on stereo colour fundus photographs using the modified WARMSG protocol. Statistical analyses included non- parametric correlations, linear regression and t-tests. Results Photopic interferometry was the best predictor of ARM status (p=0.02, r2 =-0.484). Other predictors were distance visual acuity (p =0.045, r2 0.301) and scotopic interferometry (p=0.075, r2= 0.319). When ARM status was dichotomised (no ARM versus any ARM), regression analysis showed that scotopic interferometry (p=0.002, t= 3.442) and photopic interferometry were selected by the model (p=0.022, t=2.396). Conclusions Scotopic and photopic interferometry distinguished eyes with ARM features from those with no ARM. Although no relationships could be demonstrated between achromatic and short wavelength resolution acuity and ARM status, we intend to explore the power of these tests to predict progression through different stages of ARM severity.

Keywords: age-related macular degeneration • photoreceptors: visual performance • aging: visual performance