Quantification of Nerve Fiber Layer Thickness in Normal and Glaucomatous Eyes Using Optical Coherence Tomography

Purpose: Quantitative assessment of nerve fiber layer (NFL) thickness in normal and glaucomatous eyes, and correlation with conventional measurements of the optic nerve structure and function. Methods: We studied 59 eyes of 33 subjects by conventional ophthalmologic physical examination, Humphrey 24-2 visual fields, stereoscopic optic nerve head photography, and optical coherence tomography. Results: Nerve fiber layer thickness as measured by optical coherence tomography demonstrated a high degree of correlation with functional status of the optic nerve, as measured by visual field examination ( P =.0001). Neither cupping of the optic nerve nor neuroretinal rim area were as strongly associated with visual field loss as was NFL thickness ( P =.17 and P =.21,respectively). Cupping correlated with NFL thickness only when the cup was small (cup-to-diameter ratio, 0.1 to 0.3) or large (cup-to-diameter ratio, 0.8 to 1.0) ( P =.006); there was no correlation between cupping and NFL thickness otherwise. Nerve fiber layer, especially in the inferior quadrant, was significantly thinner in glaucomatous eyes than in normal eyes ( P =.04). Finally, we found a decrease in NFL thickness with aging, even when controlling for factors associated with the diagnosis of glaucoma ( P =.03). Conclusions: Nerve fiber layer thickness can be measured using optical coherence tomography. These measurements provide good structural and functional correlation with known parameters.