Evaluation of contrast sensitivity in patients with advanced glaucoma: comparison of two tests.

Abstract

To evaluate contrast sensitivity (CS) in patients with advanced glaucomatous visual field damage, and to compare two clinical CS tests. This was a cross-sectional test-retest study. Twenty-eight patients with open-angle glaucoma, visual acuity (VA) better than 20/40 and visual field mean deviation (MD) worse than -15 dB were enrolled. Patients underwent VA, visual field and CS testing with the Pelli-Robson (PR) chart and the Freiburg Visual Acuity and Contrast Test (FrACT). Retest measurements were obtained within 1 week to 1 month. Median (IQR) age and MD were 61.5 (55.5 to 69.2) years and -27.7 (-29.7 to -22.7) dB, respectively. Median (IQR) VA was 0.08 logarithm minimum angle of resolution (0.02 to 0.16), corresponding to 20/25 (20/20 to 20/30). Median (IQR) CS was 1.35 (1.11 to 1.51) log units with the PR chart and 1.39 (1.24 to 1.64) log units with FrACT. VA explained less than 40% of the variance in CS (adjusted R²=0.36). CS estimates of both tests were closely related (rho=0.88, p=0.001), but CS was 0.09 log units higher with FrACT compared with the PR chart, and the 95% repeatability intervals (Bland-Altman) were 46% tighter with the PR chart. Despite near-normal VA, almost all patients showed moderate to profound deficits in CS. CS measurement provides additional information on central visual function in patients with advanced glaucoma.