Relationship between central corneal thickness and localized retinal nerve fiber layer defect in normal-tension glaucoma

Purpose: To determine whether central cortical thickness (CCT) is related to the extent of localized retinal nerve fiber layer (RNFL) defect at the initial examination of normal-tension glaucoma (NTG) patients. Patients and Methods: Seventy-five eyes of 75 NTG patients showing localized RNFL defects on RNFL photographs and corresponding visual field defects at the initial visit to a glaucoma specialist were selected for this Study. All participants completed refraction, Goldmann applanation tonometry, CCT measurement, stereoscopic disc photography, RNFL photography, and automated perimetry. Each patient's age, spherical equivalent, intraocular pressure, CCT, approximation of the RNFL defect to the fovea (angle a), circumferential width of the RNFL defects (angle beta), horizontal and vertical cup-to-disc ratios, and mean deviation of visual field were analyzed. Results: In univariate and multivariate analyses, lower CCT was significantly associated with increased horizontal and vertical cup-to-disc ratios, decreased angle alpha, and increased angle beta. For a decrease of 10 mu m of CCT, horizontal and vertical cup-to-disc ratios increased by 0.020, angle alpha decreased by 1.58 degrees, and angle beta increased by 1.71 degrees, respectively. Conclusion: CCT is a significant factor in predicting the extent of localized RNFL defect at the initial examination of NTG patients.