Anterior chamber depth, IOP, and thickness confounded the assessment of corneal biomechanical properties with noncontact applanation in glaucoma eyes. Compared with normal eyes, glaucoma eyes, which underwent long-term treatment or filtration surgery, had similar properties.
The purpose of this study was to evaluate corneal stiffness in primary angle-closure (PACG) and primary open-angle (POAG) glaucoma eyes that were subgrouped on the basis of the type of topical medication and filtration surgery using noncontact applanation.
All eyes were retrospectively reviewed for intraocular pressure (IOP) with Corvis-ST (OCULUS Optikgerate Gmbh, Germany). Nonglaucoma (n=140), PACG (n=102 under medication), and POAG (n=154 under medication) eyes were included. Corneal stiffness was calculated using deformation amplitude and a biomechanical model. Multivariate analyses were performed, which evaluated the effect of systemic conditions (diabetes and hypertension), the effect of medication (prostaglandins or beta blockers or combined), and the effect of filtration surgery (PACG: n=23; POAG: n=26). Age, IOP, central corneal thickness (CCT), refractive error, and anterior chamber depth (ACD) were covariates.
Diabetes and hypertension did not alter corneal stiffness of glaucoma eyes compared with nonglaucoma eyes (P>0.05). Corneal stiffness of POAG and nonglaucoma eyes was similar but significantly different from the stiffness of PACG eyes (P=0.002), irrespective of the type of topical medication. This difference was strongly correlated with ACD (P=0.003) in addition to IOP and CCT. In eyes treated with filtration surgery, ACD (P=0.04) again impacted the trends between nonglaucoma and glaucoma eyes.
Medication or filtration surgery did not affect the corneal biomechanical parameters differentially from nonglaucoma eyes. However, IOP, CCT, and ACD strongly affected corneal biomechanical parameters in the same glaucoma eyes.