Retinal Nerve Fiber Layer Thickness Analysis in Early Glaucoma

ABSTRACT

PURPOSE: To investigate the difference between superior and inferior peripapillary retinal nerve fiber layer (RNFL) thickness in early glaucoma patients who have RNFL defect in either superior quadrant or inferior quadrant and to determine if it can be useful to detect early glaucomatous change. METHODS: Eighty eight patients with early glaucoma who have RNFL defect in either the superior quadrant or the inferior quadrant as confirmed by red free photograph (40 eyes with normal standard automated perimetry and 48 eyes with early glaucomatous visual field loss) were divided into the superior RNFL defect group and the inferior RNFL defect group. The average RNFL thickness was measured in the superior and inferior quadrants using optical coherence tomography and the thickness differences between the superior and the inferior quadrants (S-I difference) were compared among early glaucoma eyes and 59 normal controls. Then, discriminative power of the S-I difference was assessed by area under ROC (AUROC). RESULTS: The average thickness of the RNFL showed a statistically significant difference between early glaucoma eyes and normal controls (P<0.05). S-I differences of the superior RNFL defect group and inferior RNFL defect group in preperimetric patients and in early perimetric patients were -20.5+/-16.4 micrometer and 15.0+/-14.2 micrometer, -24.0+/-17.2 micrometer and 18.4+/-16.7 micrometer, respectively, which were significantly greater than that of the normal control group (-8.2+/-17.1 micrometer). AUROC of S-I difference in the superior and inferior defect groups of preperimetric patients were 0.691, 0.872, respectively. CONCLUSIONS: The difference in RNFL thickness between the superior and inferior quadrants (S-I difference) in early glaucoma patients was larger than in normal controls. We expect that this parameter of RNFL analysis using OCT can be useful in detecting early glaucoma.