The sensitivity and specificity of nerve fiber layer measurements in glaucoma as determined with scanning laser polarimetry

PURPOSE: To determine the sensitivity and specificity for detecting glaucoma by scanning laser polarimetry and to assess the relation between nerve fiber layer (NFL) measurements and visual field indices. METHODS: The peripapillary NFL was divided into four segments: superior, inferior, temporal, and nasal. The mean polarimetric NFL for each segment was calculated out of six selected areas of 256 pixels each. Ratios relative to the nasal segment were determined fur the superior and inferior segments. With the use of previously obtained normograms for polarimetric NFL readings, the sensitivity of scanning laser polarimetry was assessed in 200 glaucomatous eyes (155 subjects). The specificity was assessed in a normal population of 150 eyes (150 subjects). The relation between hemifield polarimetric NFL and visual field indices was assessed by linear regression analysis. RESULTS: The sensitivity of scanning laser polarimetry was 96% and the specificity was 93%. The correlation between NFL parameters and visual field indices ranged from -0.18 to +0.26. The amount of variation by the linear regression model ranged from 3% to 6%. CONCLUSIONS: Although quantitative measurements of the NFL with scanning laser polarimetry relate poorly to visual field indices, the technique seems to be promising for screening populations for glaucoma. Whether measurements of the NFL with scanning laser polarimetry are also sensitive enough to detect change over time requires further study.