Abstract
Purpose :
Biomechanical properties of the eye are important for understanding the risk of glaucoma, but the effect of IOP reduction is poorly understood. In this study, we investigated the effect of latanoprost treatment on wave speed propagation as a measure of corneal elasticity in glaucomatous eyes.
Methods :
Twenty-four eyes from 12 subjects with POAG or NTG (62 ± 11 years, mean±SD) were included. Measurements were performed at two time points: 1. Un-medicated (prior to initiating therapy or after a 6 week washout); and 2. Medicated (after ≥6 weeks of latanoprost). IOP was measured by pneumatonometry. The ocular rigidity coefficient (OR) was calculated from IOP measured in the supine position with and without a 10 g weight added to the pneumatonometer. Axial length (AL) was measured by A-scan ultrasonography. Central corneal thickness (CCT) was measured by using Scheimpflug imaging. Corneal wave speed was determined by surface wave elastography (SWE). With this technique, a handheld shaker was placed on the closed eyelid to generate a small, 0.1 s harmonic vibration at 100 Hz. Wave propagation in the cornea was measured by SWE, and wave speed was determined from the change in phase with distance. Medicated and un-medicated measurements were compared by using generalized estimating equation models. Correlations between wave speed and other parameters were determined by regression analysis.
Results :
IOP decreased with latanoprost treatment, from 24.2 ± 6.3 mmHg to 17.2 ± 2.3 mmHg (P<0.001). There were no significant changes in corneal wave speed (2.18 ± 0.29 m/s vs 2.21 ± 0.25 m/s, P=0.58), OR (0.0212 ± 0.006 μL-1 vs 0.0215 ± 0.005 μL-1, P=0.77), CCT (554.9 ± 34.8 μm vs 552.3 ± 33.5 μm, P=0.26), and AL (24.82 ± 1.5 mm vs 24.77 ± 1.5 mm, P=0.08) with latanoprost. Corneal wave speed was moderately correlated with un-medicated IOP (r=0.55, P<0.001) but not with medicated IOP, OR, CCT, or AL (P>0.05).
Conclusions :
Corneal elasticity, as indicated by wave speed, and ocular rigidity do not change after IOP reduction with latanoprost in glaucomatous eyes. Corneal wave speed and IOP were correlated in un-medicated eyes, consistent with previous research. The lack of a correlation in medicated eyes may be due to a narrower IOP range. Further studies are required to determine the effect of IOP reduction on sclera, and the effect of other glaucoma medications.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.