Optic disc cup slope and visual field indices in normal, ocular hypertensive and early glaucomatous eyes

Abstract

Aim: To evaluate the correlation between internal slope analysis of the optic nerve head and visual field changes in normal eyes and those with ocular hypertension (OHT) and early glaucoma (POAG).

Methods: One eye of each of 22 normal subjects, 21 patients with ocular hypertension, and 50 patients with glaucoma were examined using the TopSS scanning laser ophthalmoscope. A series of topographic parameters measuring the internal features of the optic discs of these patients were obtained. These findings were compared with the Humphrey visual field analysis of these patients.

Results: Global topographic average slope and cup to disc ratio could discriminate between groups of normal and OHT patients (p = 0.02). All global and sector analysis parameters could discriminate normal subjects from POAG patients. The average slope parameter provided the best separation with a receiver operating characteristic curve area of 0.88. Visual field mean deviation (MD) was most closely correlated with global average slope (r = −0.60, p<10⁻⁷) and cup to disc ratio (r = −0.40, p<0.001). Visual field MD was also well correlated (r = −0.50, p<0.0001) with slope parameters for sectors S8, S2, and S1.

Conclusion: Average slope, a parameter independent of reference planes and magnification effects, is capable of discriminating groups of OHT and POAG patients from a group of normal subjects. This topographic parameter is also well correlated with the visual field MD. Sector slope analysis suggests early glaucomatous damage may occur in the inferotemporal region of the optic disc.