Retinal nerve fiber layer thickness measured by optical coherence tomography and its correlation with visual field defects in early glaucoma.

Abstract

To study the relationship between retinal nerve fiber layer (RNFL) thickness measured by optical coherence tomography (OCT) and visual field defects in early glaucomatous eyes and to study the diagnostic ability of OCT in distinguishing early glaucomatous eyes from normal eyes. We studied 68 eyes from primary open-angle glaucoma patients with early visual field defect (mean deviation > -6 dB), and 94 normal eyes from healthy age- and gender- matched individuals. All participants underwent 3.4-mm diameter circular OCT scans and Humphrey 30-2 mode visual field testing. The average and segmental RNFL thickness values were compared between the 2 groups. The correlation between the mean deviation in the visual field examination and RNFL thickness was evaluated. The area under the receiver operating characteristic (ROC) curve was used to distinguish normal eyes from early glaucomatous eyes. There was a significant difference in RNFL thickness between the 2 groups based on the following parameters: average thickness; superior, inferior, and nasal quadrant thickness; and 1-7, 11, 12 o'clock hour segment thickness (p < 0.05). In the glaucoma group, superior and inferior quadrant thicknesses and average RNFL thickness significantly correlated with the visual field index (superior quadrant thickness, r = 0.36; inferior quadrant thickness, r = 0.32; average RNLF thickness, r = 0.35; p < 0.05). The average RNFL and inferior quadrant thickness of early glaucomatous eyes had the widest areas under the ROC curves (0.812 and 0.793, respectively). Measurement of average and inferior quadrant RNFL thickness by OCT is useful in detecting early glaucomatous change.