Preperimetric glaucoma diagnosis by confocal scanning laser tomography of the optic disc

Aim-To evaluate the ability of confocal scanning laser tomography of the op tic nerve head to detect glaucomatous optic nerve damage in ocular hyperten sive eyes without visual held defects. Methods-The study included 50 normal subjects, 61 glaucoma patients with gl aucomatous changes in the optic disc and visual field, and 102 "preperimetr ic" patients with increased intraocular pressure, normal visual fields, and glaucomatous appearance of the optic disc as evaluated on colour stereo op tic disc photographs. For all individuals, confocal scanning laser tomograp hs of the optic nerve head were taken using the Heidelberg retina tomograph (HRT; software 2.01). Results-Almost all investigated HRT variables varied significantly (p<0.05) between the normal eyes and preperimetric glaucoma eyes with pronounced ov erlap between the two study groups. Corresponding to the overlap, sensitivi ty and specificity values were relatively low when HRT variables were taken to differentiate between normal and preperimetric glaucoma eyes. At a give n specificity of 95% highest sensitivities were found for the variables "ri m area in the superior disc sector" (24.8%), "nerve fibre layer thickness i n the inferior disc sector" (26.5%), and "rim volume in the superior disc s ector" (25.5%). A multivariate approach increased sensitivity to 42.2% at a given specificity of 95%. For the glaucoma group highest sensitivity value s were reached by rim volume in the superior disc sector (73.8%) and rim ar ea (72.1%); the multivariate approach reached 83.6%. Conclusions-Owing to pronounced overlapping between the groups, confocal sc anning laser tomography of the optic nerve head has relatively low diagnost ic power to differentiate between normal eyes and preperimetric glaucoma ey es. One of the reasons may be the biological interindividual variability of quantitative optic disc variables.