Visual acuity and contrast sensitivity in patients with neovascular age-related macular degeneration. Results from the Radiation Therapy for Age-Related Macular Degeneration (RAD-) Study

Abstract

Background: Patients with advanced age-related macular degeneration (AMD) suffer not only from impairment in central visual acuity (VA), but also from reduction in contrast sensitivity (CS). We examined VA and CS changes over time in patients with subfoveal choroidal neovascularizations (CNV) as well as the correlation between the two parameters.

Methods: VA was determined according to a standardized protocol with the Early Treatment Diabetic Retinopathy (ETDRS) chart. CS was measured with Pelli-Robson charts. The angiographic characteristics of CNV and the presence of CNV in the fellow eye as well as gender and age were evaluated as possible prognostic factors of VA and CS progression. Two hundred and five patients with neovascular AMD were recruited within the Radiation Therapy for Age-Related Macular Degeneration (RAD) Study and were reviewed over 2 years. The treatment and control groups showed no significant difference for VA or for CS ( P>0.05), and both groups were considered together.

Results: At baseline, mean VA was 55.6+/-14.5 SD letters (EDTRS chart), and mean CS was 22.8+/-6.9 letters (Pelli-Robson chart). Spearman Correlation Coefficient ( r(s)) between VA and CS was r(s)=0.60, P=0.0001. Over 2 years the mean VA loss was 23.6+/-21.4 letters and mean CS reduction was 9.0+/-9.7 letters. Agreement between change of VA and change of CS was moderate ( r(s)=0.65, P=0.0001; kappa coefficient (grouped into VA loss < or =15, >15, >30 letters; CS loss < or =6, >6, >15 letters) kappa=0.43, 95% CI [0.32;0.54]). Proportional hazard models did not show any apparent influence of type of CNV, or CNV in the fellow eye, on change in VA and CS.

Conclusion: The results indicate that VA and CS do not always show the same progression in visual function loss although they show a moderate correlation in eyes with neovascular AMD. Both parameters provide important information about visual disability and should be evaluated as outcome in interventional studies.