Detection of Glaucoma With Scanning Laser Polarimetry

Abstract

To determine which retinal nerve fiber layer (RNFL) measures obtained with scanning laser polarimetry are most useful in detecting early to moderate glaucomatous visual field loss.Subjects and Methods: One eye from 84 healthy individuals and 83 patients with early to moderate glaucomatous visual field loss (167 eyes) was assessed with a scanning laser polarimeter (Laser Diagnostic Technologies, San Diego, Calif). Three separate scans were obtained, and a baseline scan was created and used in the analyses. Integrated software (program GDx, version 1.0.02; Laser Diagnostic Technologies) was evaluated by assessing its sensitivity and specificity for detecting early and moderate glaucomatous visual field loss. Fisher linear discriminant functions also were developed in this population to assess sensitivity and specificity and were compared with the GDx analyses.Results: There were statistically significant differences between the healthy and glaucomatous eyes for 14 of the 15 RNFL measures (P = .001). However, considerable overlap in measurements between groups was found. With the GDx number, the area under the receiver operator characteristic (ROC) curve was 0.78, and the sensitivity and specificity were 82% and 62%, respectively. Applying the best discriminant function using 3 variables (average thickness, ellipse modulation, and average ellipse thickness) to our study population resulted in an area under the ROC curve of 0.89 and a sensitivity and specificity of 74% and 92%, respectively.Conclusions: A combination of RNFL measures obtained using the scanning laser polarimeter improved the ability to differentiate between healthy eyes and eyes with early and moderate glaucomatous visual field loss. Analyses using GDx software did not differentiate between healthy and glaucomatous eyes as well as the discriminant analysis function did.

Scanning laser polarimetry in patients with acute angle-closure glaucoma

“…[7][8][9]17 Weinreb et al 7 found that with the exception of symmetry, there were statistically significant differences between healthy and glaucomatous eyes with GDx parameters that include the GDx number, superior ratio, inferior ratio, superior/nasal ratio, maximum modulation, superior maximum, inferior maximum, ellipse modulation, average thickness, ellipse average, superior average, inferior average, and superior integral.…”

“…The definitions of these parameters have been described elsewhere. 6,7 Statistical analyses were performed using JMP software (SAS Institute, Cary, NC, USA). Mann-Whitney tests with Bonferroni correction were used to evaluate differences between both study groups for the 12 standard GDx parameters, the RNFL thickness from the nasal and temporal averages, BCVA, refraction (spherical equivalent), visual field indices including mean defect (MD), and CPSD.…”

“…5,6 The quantification of RNFL thickness using the GDx in normal subjects, patients with ocular hypertension (OH) and primary open-angle glaucoma (POAG), has been described in various studies. [7][8][9] Primary angle-closure glaucoma (PACG) is the most frequent form of glaucoma in Mongolian-type Asian populations. The prevalence of PACG varies by race, ranging from 0.1% in Caucasians, to 1.3% in Chinese populations, and up to 5% in Eskimos over 40 years of age.…”

Automated detection of wedge-shaped defects in polarimetric images of the retinal nerve fibre layer

“…[9][10][11][12] Most of these studies explored the standard parameters provided by the GDx (described elsewhere 13 ) or combinations of these (some including the built-in classifier named The Number). Despite their fair to excellent performance, these parameters may be quite insensitive to wedge defects, especially narrow ones, since they are based either on general statistics of measurements along an ellipse around the optic disc or on measurements in a fairly large area, such as an image quadrant.…”

Comparison between fixed-angle and customised corneal-polarisation compensation methods in scanning laser polarimetric measurement of the retinal nerve fibre layer in glaucoma

“…[1][2][3][4][5] The technique is based on the optical retardation of the illuminating laser beam, which is produced by the parallel retinal nerve fibres around the optic nerve head. 6 The optical retardation caused by the retinal ganglion cell axons has been shown to have a linear relationship with the anatomical thickness of the retinal nerve fibre layer (RNFLT), and is therefore suitable for the detection of retinal nerve fibre loss.…”