Predicting Subsequent Visual Field Loss in Glaucomatous Subjects With Disc Hemorrhage Using Retinal Nerve Fiber Layer Polarimetry

Abstract

To predict progression of visual field loss after an episode of disc hemorrhage in glaucoma patients on the basis of retinal nerve fiber layer (RNFL) GDx polarimetry measurements analyzed by wavelet-Fourier analysis (WFA). Retrospective GDx data from 16 subjects (10 progressors and 6 non-progressors based on visual fields) obtained near the time of disc hemorrhage were analyzed to predict which patients would have visual field progression. Polarimetry scans throughout a follow-up period (31 months average) were also analyzed to compare field progression to RNFL thickness change after the hemorrhage. Mean RNFL thickness inferred from the polarimetry data at sixteen 22.5 degrees sectors at distances of 1.6, 1.7, and 1.8 disc diameters were used. Data were analyzed by applying to appropriate regions of disc hemorrhage patients a structural analysis (WFA) we had developed previously. A linear discriminant function (Fischer) was produced and a leave-one-out method using separate training and test data was used to assure validity of the results. Patients who subsequently progressed were successfully predicted with moderate success (sensitivity / specificity was 0.77 / 0.88 with ROC area = 0.858). A separate analysis comparing pre- and post-hemorrhage RNFL sector thickness revealed clear evidence of RNFL thinning at the inferior and superior sectors before progression of visual field. The thinning of RNFL thickness was not restricted to regions corresponding to the location of the hemorrhage. Wavelet-Fourier analysis can differentiate progressors from non-progressors with moderate accuracy. Comparison to a prior study of this same cohort emphasizes that relatively small regions must be considered (as opposed to larger quadrants) to see these significant changes in RNFL.