Measurement of peripapillary retinal nerve fiber layer volume in glaucoma

PURPOSE: To measure peripapillary retinal nerve fiber layer volume in normal subjects and patients with ocular hypertension, primary open-angle glaucoma, and low-tension glaucoma. METHODS: Sixty-five subjects were classified into four groups of normal subjects and subjects with ocular hypertension, primary open-angle glaucoma, and low-tension glaucoma on the basis of intraocular pressure measurements, visual field loss, and optic disk appearance. Groups were matched for sex, age, and optic disk area. Peripapillary retinal nerve fiber layer volume measurements were made with a modification of software version 1.11 of the Heidelberg Retina Tomograph confocal scanning laser ophthalmoscope. Retinal nerve fiber layer volume measurements were taken at 0.1-mm increments from the disk margin for a global 360-degree assessment and at four predefined segments using two different reference planes. Statistical analysis was carried out using analysis of variance with Bonferroni correction. RESULTS: Retinal nerve fiber layer volume measurements showed a gradation from normal to ocular hypertension and from ocular hypertension to glaucoma groups. Mean group measurements showed statistically significant differences ( P < .05) in peripapillary retinal nerve fiber layer volume for most segmental measures between the groups. Measurements with the default reference plane in the 0.0-mm to 0.1-mm and 0.1-mm to 0.2-mm increments for the superotemporal segment showed the greatest differences between groups ( P < .00005). CONCLUSION: Peripapillary retinal nerve fiber layer volume measurements differ between groups of normal subjects and patients with ocular hypertension, primary open-angle glaucoma, and low-tension glaucoma. This measure offers a further method of assessment of retinal nerve fiber layer in patients with glaucoma and glaucoma suspects.