Dianosis of Glaucoma by Laser Polarimeter With Three Diameter Rings

Abstract

Abstract: : Purpose: To measure retinal nerve fiber layer (RNFL) thickness by scanning laser polarimeter with three different diameter rings and to develop a linear discriminant function using measurements with these rings. We also evaluated this analysis method for diagnosing glaucoma. Methods: RNFL thickness estimates were obtained from 51 healthy individuals and 160 glaucoma patients with GDx VCC (Laser Diagnostic Technology). They were analyzed with three diameter rings; small ring (1.2 mm outside the disc), medium ring (1.6 mm outside the disc) and large ring (2.0 mm outside the disc). The values were entered into linear discriminant analysis. Receiver operating characteristic (ROC) curve were used to compare the performance of the 3–ring metrics against other commonly used RNFL analytical procedures. Results: : In healthy individuals, mean thickness analyzed with small ring was 54.95 ± 6.13 µm. Mean thickness with middle and large rings was 0.87– and 0.79– fold of mean thickness with small ring, respectively and was significantly correlated with that with small ring (r = 0.945, P < 0.0001; r = 0.850, P < 0.0001). In patients with glaucoma, mean thickness with small ring was 49.05 ± 14.36 µm. Mean thickness with middle and large rings was 0.90– and 0.84– fold of mean thickness with small ring, respectively, and significantly correlated with that with small ring (r = 0.987, P < 0.0001; r = 0.963, P < 0.0001). In healthy individuals and glaucoma patients, similar results were obtained for superior and inferior average. Sensitivity and specificity for the linear discriminant function based on the analysis with three rings was 76% and 84%, respectively, and the area under the ROC curve was 0.901. These values were better than those determined using measurements with any single ring. Conclusions: Measurements of RNFL thickness with three different rings showed strong correlations with each other. The discriminant function based on the output from RNFL data with three rings resulted in better diagnostic capability compared with other common RNFL analytical procedures.

Keywords: nerve fiber layer • imaging/image analysis: clinical