Ranking of optic disc variables for detection of glaucomatous optic nerve damage

PURPOSE. TO describe optic disc variables assessed by evaluation of clinica l optic disc photographs and to compare sensitivity and specificity of thes e optic disc parameters in identifying patients with ocular hypertension wh o have nerve fiber layer defects and normal visual fields and patients with visual held defects. METHODS. The study included 500 normal subjects, 132 patients with ocular h ypertension with retinal nerve fiber layer defects and normal visual fields (preperimetric glaucoma), and 840 patients with glaucomatous visual field defects. Color stereo optic disc photographs were morphometrically evaluate d. RESULTS. Highest diagnostic power for the separation between the normal gro up and the preperimetric glaucoma group had the vertical cup-to-disc diamet er ratio corrected for its dependence on the optic disc size, total neurore tinal rim area, rim-to-disc area ratio corrected for disc size, and cup-to- disc area ratio corrected for disc size. Diagnostic power was lower for rim area in the temporal inferior and temporal superior disc sector, cup area corrected for (disc size, and horizontal cup-to-disc diameter ratio correct ed for disc size. Less useful for the differentiation between the normal su bjects and the preperimetric glaucoma group were size of zones alpha and be ta of parapapillary chorioretinal atrophy, and ratios of neuroretinal rim w idth and rim area comparing various optic disc sectors with each other. CONCLUSIONS. In subjects with ocular hypertension with retinal nerve fiber layer defects and normal conventional achromatic visual fields, the vertica l cup-to-disc diameter ratio corrected for optic disc size, total neuroreti nal rim area, rim-to-disc area ratio, and cup-to-disc area ratio corrected for disc size are the most valuable optic disc variables for early detectio n of glaucomatous optic nerve damage. Correction for optic disc size is nec essary for optic disc variables directly or indirectly derived from the opt ic cup. Parapapillary atrophy is less important in the early detection of g laucoma.