Computer measurement of retinal nerve fiber layer striations

Abstract

An image analysis method to measure retinal nerve fiber layer (RNFL) striations from digitized fundus photographs was developed to improve detection and monitoring of progressive diffuse RNFL loss. Striations were measured by comparing the high spatial frequency variability across with the variability along the RNFL. This locally normalized measure of striations compensates for the wide density variations both within individuals and between individuals and RNFL photographs. Five repeated measurements were taken at each of three locations from each retinal image. Measurements from five patients with recorded visual field loss due to optic nerve diseases were compared with five normal subjects and five suspect eyes. Measurements clearly distinguished the three groups when taken at the temporal arcades. Measurements above and below the arcades were also consistent, but did not distinguish normals from suspects. The measure was correlated with graded estimates of RNFL integrity of two trained observers (rho = -0.57, p < 0.001 and rho = -0.61, p < 0.001).