Corneal Hysteresis and Rates of Neuroretinal Rim Change in Glaucoma

Abstract

To evaluate the impact of corneal hysteresis (CH) as a risk factor for progressive neuroretinal rim loss in glaucoma, as measured by spectral-domain OCT of the Bruch's membrane opening minimum rim width (MRW). Prospective, observational cohort study. The study group included 118 eyes of 70 subjects with glaucoma. The average follow-up time for the cohort was 3.9 ± 1.3 years, with an average of 6.4 ± 2.0 spectral-domain OCT tests, ranging from 4 to12. Corneal hysteresis measurements were acquired at baseline using the Ocular Response Analyzer (Reichert Instruments). Linear mixed models were used to investigate the relationship between the rates of MRW loss and baseline CH. Multivariable analyses adjusted for other putative predictive factors for progression, including mean intraocular pressure (IOP), central corneal thickness (CCT), age, race, and baseline disease severity. Effects of CH on the rate of MRW change over time. Corneal hysteresis had a significant effect on rates of MRW progression over time. Each 1-mmHg lower CH was associated with-0.38 μm/year faster MRW loss (95% confidence interval [CI],-0.70 to-0.06; P=0.019), after adjustment for other predictive factors. The mean IOP was also significantly associated with progression, with-0.35 μm/year (95% CI,-0.47 to-0.23 μm/year) faster MRW change for each 1-mmHg higher pressure (P < 0.001). In the analysis of predictive strength, the mean IOP was the strongest predictive factor (R2=23%), followed by CH (R2= 14%) and baseline disease severity (R2= 6%). Central corneal thickness explained only 3% of the variability in slopes of change in global MRW. Lower CH measurements were associated with faster loss of the neuroretinal rim in glaucoma, as measured by MRW. The predictive ability of CH was superior to that of CCT. These findings suggest that CH is an important parameter to be considered in assessing the risk of glaucoma progression.