Correlation of Relative Afferent Pupillary Defect and Retinal Nerve Fiber Layer Loss in Unilateral or Asymmetric Demyelinating Optic Neuropathy

Abstract

To investigate the relationship between relative afferent pupillary defect (RAPD) and retinal nerve fiber layer (RNFL) thickness assessed by optical coherence tomography (OCT) in patients with unilateral or asymmetric demyelinating optic neuropathy. Seventy-two patients with unilateral or asymmetric demyelinating optic neuropathy were retrospectively evaluated. RAPD was measured by the swinging flashlight method using neutral density filters, and RNFL thickness was measured with the OCT. Relationships between RAPD and RNFL thickness difference/ratio between the two eyes (in superior, inferior, temporal, nasal quadrants and total thickness) were evaluated by linear regression. Coefficients of determination (R(2)) were calculated using a multivariate model. The mean RNFL thickness in the more affected eyes was 82.7 +/- 18.7 microm, and in the fellow eyes it was 88.9 +/- 13.97 microm (R(2) = 0.406; P < 0.0001). RAPD size correlated significantly with both RNFL thickness difference (total: R(2) = 0.191, P < 0.0001; superior: R(2) = 0.203, P < 0.0001; inferior: R(2) = 0.126, P = 0.002; temporal: R(2) = 0.059, P = 0.040; nasal: R(2) = 0.062, P = 0.035) and RNFL thickness ratio (total: R(2) = 0.325, P = 0.0001; superior: R(2) = 0.339, P < 0.0001; inferior: R(2) = 0.256, P < 0.0001; temporal: R(2) = 0.151, P = 0.0001; nasal: R(2) = 0.156, P = 0.001). RAPD as measured in log units significantly correlated with total and quadrantic RNFL thickness differences and ratios. Total, superior, and inferior quadrant data produced the strongest correlations.