Keratometry, Optic Disc Dimensions, and Degree and Progression of Glaucomatous Optic Nerve Damage

Abstract

To evaluate whether keratometric readings as a measure of corneal shape are associated with optic disc dimensions and with the degree and rate of perimetric progression of chronic open-angle glaucoma or ocular hypertension. The hospital-based observational study included 1826 eyes of 936 patients with ocular hypertension, patients with chronic open-angle glaucoma, or normal individuals. For 733 ocular hypertensive or glaucomatous eyes, follow-up examinations were performed with a mean follow-up time of 58.0+/-34.7 months. Observation procedures were keratometry, morphometric optic disc analysis, tonometry, and perimetry. In the normal study group, area of the neuroretinal rim, alpha zone and beta zone of parapapillary atrophy, and retinal vessel diameter were not significantly associated with keratometric readings. In the entire study population, the optic disc area was significantly (P<0.001; r=-0.27) correlated with low keratometric readings as expressed in diopters. Keratometric readings were significantly (P<0.001 adjusted for age, intraocular pressure, baseline damage, and corneal asphericity) smaller in the normal-pressure glaucoma group than in the normal study group and in the groups with ocular hypertension or primary and secondary open-angle glaucoma. Rate of perimetric progression was not significantly associated with low keratometric readings, either in simple or in multiple Cox regression analysis, controlling for baseline damage, ocular hypertension, age, corneal asphericity, and intraocular pressure. Large optic disc area is statistically significantly, but clinically weakly, correlated with low keratometric readings (diopters). In Caucasian individuals with ocular hypertension and patients with chronic open-angle glaucoma, the rate of development or progression of glaucomatous visual field defects is not significantly associated with keratometric readings.