Linear Discriminant Function for Detecting Glaucomatous Optic Nerve Damage

ABSTRACT

PURPOSE: To determine whether the linear discriminant function of optic disc parameters measured with confocal scanning laser tomography can improve the differentiation between normal and glaucoma eyes. METHODS: One eye was randomly selected from 92 normal subjects and 154 primary open-angle glaucoma patients. The Humphrey perimeter, program C 30-2 visual fields, and 13 Heidelberg Retina Tomograph parameters (software 2.01, includes rim to disc area ratio) were utilized. Glaucoma was defined as an abnormal visual field and intraocular pressure greater than 22 mm Hg. The appearance of the optic nerve head was not taken as a diagnostic criterion. Because some of the optic disc parameters depend on the size of the optic disc, these parameters were corrected for the effect of disc area. RESULTS: Stepwise discriminant analysis indicated that the most valuable optic disc parameters for the detection of glaucomatous optic nerve damage were rim area for the early glaucoma group (65 eyes, average mean deviation [MD] = -3.43 +/- 1.60 dB) and mean retinal nerve fiber layer thickness, rim volume, and rim area for the moderate glaucoma group (49 eyes, average MD = -8.75 +/- 1.88 dB). The sensitivity, specificity, and accuracy were 69%, 71%, and 70%, respectively, for the early glaucoma group and 78%, 92%, and 87%, respectively, for the moderate glaucoma group. CONCLUSIONS: The linear discriminant function was not sensitive enough to detect early glaucomatous optic nerve damage. Hence the result of discriminant analysis has to be interpreted in the context of all other clinical data available.