Ranking of optic disc variables for detection of glaucomatous optic nerve damage
J. B. Jonas1, A. Bergua1, P. Schmitz-Valckenberg2, K. I. Papastathopoulos1
Purpose: To describe optic disc variables assessed by evaluation of clinical optic disc photographs, and to compare sensitivity and specificity of these optic disc parameters in identifying ocular hypertensive patients with nerve fiber layer defects and normal visual fields, and patients with visual field defects.
Methods: The study included 500 normal subjects, 132 ocular hypertensive patients 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 evaluated.
Results: Highest diagnostic power for the separation between the normal group and the preperimetric glaucoma group had the vertical cup/disc diameter ratio corrected for its dependence on the optic disc size, total neuroretinal rim area, rim/disc area ratio corrected for disc size, and cup/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/disc diameter ratio corrected for disc size. Less useful for the differentiation between the normal subjects and the preperimetric glaucoma group were size of zones alpha and beta of parapapillary chorioretinal atrophy.
Conclusions: In ocular hypertensive subjects with retinal nerve fiber layer defects and normal conventional achromatic visual fields, the vertical cup/disc diameter ratio corrected for optic disc size, total neuroretinal rim area, and rim/disc area ratio and cup/disc area ratio corrected for disc size belong to the most valuable optic disc variables to detect glaucomatous optic nerve damage early. Correction for optic disc size is necessary for optic disc variables directly or indirectly derived from the optic cup. Parapapillary atrophy is less important for the early detection of glaucoma.
(1) Department of Ophthalmalogy, University Erlangen-Nürnberg, D-91054 Erlangen (2) Department of Ophthalmology, Evangelisches Stift Hospital, D-56068 Koblenz