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

Abstract

Précis: Corneal hysteresis and pulsatile ocular blood volume were significantly lower in the eye with greater damage in asymmetric glaucoma, without a difference in intraocular pressure or central corneal thickness, and no difference in elastic parameters. Purpose: To compare biomechanical and vascular metrics between eyes of subjects with asymmetric glaucoma (ASYMM) and those with symmetric glaucoma (SYMM). Methods: Forty-five subjects were prospectively recruited and divided into ASYMM, defined as cup-to-disc ratio (C/D) 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 corneal hysteresis (CH), and elastic parameters from the Corvis ST including stiffness parameter at first applanation (SP-A1), stiffness parameter at highest concavity (SP-HC), integrated inverse radius (IIR) deformation amplitude ratio (DAR). Intraocular pressure (IOP), Central Corneal Thickness (CCT), Mean Deviation (MD), Ganglion Cell Complex (GCC), and Pulsatile Ocular Blood Volume (POBV) were included. Paired t-tests were performed between eyes in both groups. Statistical analyses were performed with SAS using significance threshold of P<0.05. Results: For ASYMM (16 subjects), 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 to BEST. No other parameters were significantly different. For SYMM (29 subjects), 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 is a new clinical parameter that may indicate reduced blood flow is also associated with greater damage.