Reproducibility of Optic Nerve Head Topographic Measurements with the Glaucoma-Scope

Abstract

Our purpose was to evaluate the reproducibility of optic nerve head depth measurements using the Glaucoma-Scope. Optic nerve head topography was measured with the Glaucoma-Scope in 10 normal subjects and in 10 patients with glaucoma. Five separate readings were obtained by a single observer from one eye of each subject on the same day. Mean depth values were calculated for the overall disc, each quadrant, and areas overlying vessels at those points at which the change from baseline exceeded 50 mum. Similar calculations were made for actual depth measurements in regions of potential clinical interest, including the bottom of the cup, the temporal slope, the nasal disc, and a peripapillary region, as well as 15 randomly selected single points. Reproducibility of the depth values was determined by calculating standard deviations, coefficients of variation, and 95% confidence intervals in the five separate measurements. The mean standard deviations in regions of potential clinical interest among the 20 subjects ranged from 3.98 mum to 14.09 mum, and the mean coefficient of variation ranged between 4.2% and 8.7%. The 95% confidence intervals for the total population ranged from 9.88 mum to 34.97 mum for the regions of interest and was 43 mum for the 15 random points. There was no statistically significant difference in reproducibility between the two groups of subjects. In this study the Glaucoma-Scope produced quantitative optic nerve head topographic measurements that were highly reproducible, within a tolerance of <50 mum.