Biomechanical and Vascular Metrics Between Eyes of Patients With Asymmetric Glaucoma and Symmetric Glaucoma

Abstract

Précis: Corneal hysteresis (CH) and pulsatile ocular blood volume (POBV) were significantly lower in the eye with greater damage in asymmetric glaucoma, without a difference in intraocular pressure (IOP) or central corneal thickness (CCT), and no difference in elastic parameters. Objective: To compare biomechanical and vascular metrics between the eyes of patients with asymmetric glaucoma (ASYMM) and those with symmetric glaucoma (SYMM). Patients and Methods: Forty-five patients were prospectively recruited and divided into ASYMM, defined as cup-to-disc (C/D) ratio difference >0.1 between eyes and SYMM, with C/D difference ≤0.1. For ASYMM, the smaller C/D was defined as the best eye (“best”) and the fellow eye was defined as the worst eye (“worse”). All metrics were subtracted as “worse” minus “best,” including the viscoelastic parameter CH, and elastic parameters from the Corvis ST, including stiffness parameter at first applanation, stiffness parameter at highest concavity, integrated inverse radius, deformation amplitude ratio, IOP, CCT, mean deviation (MD), ganglion cell complex (GCC), and POBV were included. Paired t tests were performed between eyes in both groups. Statistical analyses were performed with SAS using a significance threshold of P <0.05. Results: For ASYMM (16 patients), “worse” showed significantly lower CH (−0.76 ± 1.22), POBV (−0.38 ± 0.305), MD (−3.66 ± 6.55), and GCC (−7.9 ± 12.2) compared with “best.” No other parameters were significantly different. For SYMM (29 patients), there were no significantly different metrics between eyes. Conclusions: Lower CH, POBV, GCC, and worse MD were associated with greater glaucomatous damage in asymmetric glaucoma without a difference in IOP or CCT. Lower CH and GCC are consistent with previous studies. POBV, a new clinical parameter that may indicate reduced blood flow, is also associated with greater damage.