Corneal biomechanics measured with the ocular response analyser in patients with unilateral open-angle glaucoma

Purpose: To evaluate the relationship between biomechanical properties of the cornea and intraocular pressure (IOP) and the role of biomechanical properties in eyes of patients with unilateral primary open-angle glaucoma (POAG). Methods: The biomechanical properties of corneal hysteresis (CH) and the corneal resistance factor (CRF) were measured with the ocular response analyser (ORA). In an experimental setting, three human donor eyes with Schiotz-tonometry-controlled IOP were investigated. In addition, a series of patients with unilateral POAG were evaluated. Main outcome measures were CH, CRF, corneal-compensated IOP (IOPcc), standard automated perimetry parameters mean defect (MD) and pattern standard deviation, central corneal thickness, Goldmann applanation tonometry (GAT), and cup-to-disc ratio. Results: A highly significant linear correlation between CH and the corneal-compensated IOP (IOPcc, r = -0.926; p < 0.001) was found. The correlation between IOP(CC) and CRF was not significant (r = 0.335; p = 0.08). In total, 36 eyes of 18 patients with unilateral POAG were examined. Regarding uncorrected CH (mean 7.73 +/- 1.46 mmHg glaucomatous eye and 9.28 +/- 1.42 mmHg fellow eye), there was a highly significant difference between both eyes. This difference disappears, when CH was corrected for IOP (9.44 +/- 3.78 mmHg and 9.97 +/- 3.22 mmHg, respectively). Conclusions: Corneal hysteresis but not corneal resistance factor is dependent on IOP. In patients with unilateral POAG, IOP is higher in the affected eye. When CH is corrected for IOP, corneal biomechanical properties do not differ in both eyes of patients with unilateral POAG.