PURPOSE:The aim of the present study was to test the hypothesis that the three-dimensional (3-D) topography of the optic disc contains sufficient information to diagnose glaucoma with a high degree of reliability. METHODS:The Zeiss 'Confocal Laser Scanning Ophthalmoscope' (CLSO) was used to obtain digitized samples of 3-D images of optic nerve heads from the following three groups of patients: (i) 40 normals with normal optic discs, normal Humphrey 24-2 full threshold visual fields and an intraocular pressure (IOP) < or = 21 mmHg, (ii) 20 established glaucoma patients with cupping, glaucomatous field loss and an IOP > 21 mmHg; and (iii) 20 early glaucoma patients with early cupping, field loss with a mean defect less than -10 dB and IOP > 21 mmHg. The cupping in these patients was paramaterized by spherical harmonics and was classified by multivariate statistical analysis. RESULTS:Of 40 glaucoma patients, 39 were correctly classified. Of 40 normal patients one was classified as glaucoma. CONCLUSIONS:This study demonstrates that the CLSO, with the use of spherical harmonics, can differentiate glaucomatous from normal optic discs in this selected group of patients without the need for a skilled observer. This constitutes a promising technique to be tested on a large, unselected body of patients as a screening tool.