Contrast-sensitivity testing with scanning-laser ophthalmoscope stimulation in normal, ocular hypertensive, and glaucomatous patients.

Abstract

The purpose of this study was to test the usefulness of the scanning laser ophthalmoscope (SLO) as a stimulator for localized contrast-sensitivity (CS) measurements under visual control in normals and glaucomatous patients. The helium-neon laser (630 nm) of a Rodenstock SLO was used to generate a localized square-wave stripe pattern and a fixation mark while an infrared laser (780 nm) visualized the eye's fundus. Thus, measurements with unstable fixation could be discarded. The spatio-temporal CS was determined with a localized alternating pattern as follows: 5 Hz, 2.88 cycles/degree; stimulus diameter 2 degrees; test location central, temporal upper, and temporal lower retinal area. The subjects included 47 controls, 23 ocular hypertensive patients (intraocular pressure > 21 mmHg, normal optic disc, no visual field defect), 27 "preperimetric" glaucoma patients (intraocular pressure > 21 mmHg, early glaucomatous optic disc damage, no visual field defect), and 41 "perimetric" glaucoma patients with glaucomatous defects of the optic disc and perimetric losses. Nonparametric tests (Wilcoxon, Spearman) were used for statistical analyses. Among the three locations tested, CS values recorded for the temporal lower retinal areas showed the strongest reduction in glaucomas ("preperimetric" P = 0.002, "perimetric" P < 0.0001) and a significant correlation with the perimetric mean defect of the stimulated area (r = 0.65, P < 0.001). In all, 95% of glaucomatous eyes with extensive visual field losses were recognized as pathologic at a specificity of 80%. Spatiotemporal CS of temporal retinal areas is sensitive to glaucoma. The present study confirms the feasibility of using the SLO system for localized CS measurements, in normals and patients.