Assessment of Corneal Biomechanical Properties in Normal Tension Glaucoma and Comparison With Open-angle Glaucoma, Ocular Hypertension, and Normal Eyes

Purpose: To assess the biomechanical properties of corneas in patients with normal tension glaucoma (NTG) and to compare them with those of patients with primary open-angle glaucoma (POAG), ocular hypertension (OHT), and normal controls (N). Methods: Corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann intraocular pressure (IOPg), and corneal compensated IOP (IOPcc) were obtained using an ocular response analyzer for 28 eyes in 14 patients with NTG, 75 eyes in 38 patients with chronic POAG, 53 eyes of 27 patients with OHT, and 44 eyes of 22 N controls. IOP using Goldmann applanation tonometry (IOPGA) and ultrasonic central corneal thickness (CCT) were also measured for each eye. Analysis of variance test was used for statistical analysis. Results: CH was significantly lower in the NTG group (9.88 +/- 2.02 mm Hg) compared with the N group (11.05 +/- 1.53 mm Hg; P < 0.01). CRF was significantly lower in the NTG group (9.5 +/- 1.89 mm Hg) compared with the POAG group (11.15 +/- 2.35 mm Hg; P < 0.01) and to the N group (11.00 +/- 1.75 mm Hg; P < 0.01). CCT was not considered significantly different between the 4 groups. However, IOPcc was found to be significantly lower in NTG group compared with the POAG group and OHT group (P < 0.001). Conclusion: NTG was associated with significantly lower CRF than chronic POAG and N patients. CH and CRF could be a useful tool in early diagnosis of NTG.