Abstract
Purpose :
To compare corneal and ocular biomechanical parameters in phakic, pseudophakic and aphakic subjects with open angle glaucoma.
Methods :
The present study includes 83 eyes of 43 phakic patients with primary open angle glaucoma (POAG), 16 eyes of 10 pseudophakic patients with POAG, and 4 eyes of 2 subjects with aphakic glaucoma, all prospectively enrolled. Biomechanical data were acquired using the Corvis ST and Ocular Response Analyzer (ORA). Additionally, central corneal thickness (CCT) was obtained from the Corvis ST and intraocular pressure (IOP) was recorded by dynamic contour tonometry (DCT). Parameters compared include corneal hysteresis (CH), stiffness parameter at first applanation (SP-A1) and highest concavity (SP-HC) and integrated inverse radius. ANCOVA was used to compare ORA data between groups using corneal compensated IOP (IOPCC) as a covariate, and to compare Corvis ST data between groups using DCT as a covariate. The statistical analysis was performed with SAS and significance threshold was set at P<0.05. Due to a low n, the aphakic cohort was excluded from statistical analysis.
Results :
T-tests revealed no significant between-group differences in IOPCC (17.37 ± 4.41 vs 15.74 ± 2.81; p=0.1607), DCT (18.65 ± 3.78 vs 17.07 ± 2.46; p=0.1114), or CCT (545.74 ± 34.28 vs 538.63 ± 39.32; p=0.4595). CH was significantly greater in the phakic group (9.55 ± 1.9 vs 9.11 ± 1.82; p<0.0001) after controlling for IOPCC. Integrated inverse radius was greater in the pseudophakic group (8.47 ± 0.99 vs 7.79 ± 0.92; p<0.0001) after controlling for DCT. There were no significant differences in corneal (SP-A1) or scleral (SP-HC) stiffness, although the n in the pseudophakic group was too low to be conclusive. Qualitatively, aphakic eyes had a greater unadjusted mean IOPCC, DCT, CCT, SP-A1, SP-HC and CH than both the phakic and pseudophakic cohorts.
Conclusions :
Pseudophakic eyes with POAG demonstrated lower stiffness (resistance to deformation) and lower damping (ability to dissipate energy) than phakic eyes. We propose that the contents of the eye affect its response to air-puff-induced deformation, and that the presence of a crystalline lens aids in energy dissipation and limits fluid displacement in the concave corneal phase leading to a stiffer response when compared to pseudophakic eyes. More data are needed to compare the biomechanics of eyes with aphakic glaucoma.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.