Reproducibility of topographic measures of the glaucomatous optic nerve head.

AIMS/BACKGROUND Laser scanning tomography provides an assessment of three dimensional optic disc topography. For the clinical purpose of follow up of glaucoma patients, the repeatability of the various measured variables is essential. In the present study, the reproducibility of morphometric variables calculated by the topographic scanning system, TopSS (Laser Diagnostic Technology, San Diego, CA) was investigated. METHODS Two independent measurements (30 minutes apart) each consisting of three complete images of the optic disc were performed on 16 eyes of 16 glaucoma patients using a TopSS. The instrument calculates 14 morphometric variables for the characterisation of the optic disc. RESULTS From the two tailed paired tests, all variables were seen to have good reproducibility. However, correlation and regression analyses showed that only the three variables, volume below, half depth area, and average cup depth, are acceptably reproducible. CONCLUSION The TopSS provides three variables which describe the physiological shape of the optic disc that have high reproducibility. These three variables might be useful for following the progression of optic disc changes in glaucoma patients.