Corneal hysteresis as a risk factor for glaucoma progression: a prospective longitudinal study

Abstract

Purpose: To evaluate the role of corneal hysteresis (CH) as a risk factor for the rate of visual field progression in a cohort of patients with glaucoma followed prospectively over time.

Design: Prospective observational cohort study.

Participants: The study group included 114 eyes of 68 patients with glaucoma followed for an average of 4.0 ± 1.1 years. Visual fields were obtained with standard automated perimetry. Included eyes had a median number of 7 (range, 5-12) tests during follow-up.

Methods: The CH measurements were acquired at baseline using the Ocular Response Analyzer (Reichert Instruments, Depew, NY). Evaluation of rates of visual field change during follow-up was performed using the visual field index (VFI). Linear mixed models were used to investigate the relationship between rates of visual field loss and baseline CH, baseline intraocular pressure (IOP), and central corneal thickness (CCT), while adjusting for potentially confounding factors. An interaction term between IOP and CH was included in the model to investigate whether the effect of IOP on rates of progression depended on the level of CH.

Main outcome measures: Effects of CH, IOP, and CCT on rates of VFI loss over time.

Results: The CH had a significant effect on rates of visual field progression over time. In the univariable model including only CH as a predictive factor along with time and their interaction, each 1 mmHg lower CH was associated with a 0.25%/year faster rate of VFI decline over time (P<0.001). The multivariable model showed that the effect of IOP on rates of progression depended on CH. Eyes with high IOP and low CH were at increased risk for having fast rates of disease progression. The CH explained a larger proportion of the variation in slopes of VFI change than CCT (17.4% vs. 5.2%, respectively).

Conclusions: The CH measurements were significantly associated with risk of glaucoma progression. Eyes with lower CH had faster rates of visual field loss than those with higher CH. The prospective longitudinal design of this study supports the role of CH as an important factor to be considered in the assessment of the risk of progression in patients with glaucoma.

Financial disclosure(s): Proprietary or commercial disclosure may be found after the references.

Figure 1

Scatterplot matrix illustrating the relationship between corneal hysteresis, corneal thickness and Goldmann applanation tonometry (GAT) measurements. IOP = intraocular pressure; CH = corneal hysteresis

Figure 2

Relationship between Visual Field Index (VFI) values over time and corneal hysteresis measurements as predicted by the linear mixed model. For illustrative purposes, eyes were divided into those with corneal hysteresis lower than 10mmHg and greater than or equal to 10mmHg. The plot shows that eyes with lower corneal hysteresis values tended to show worse declines of VFI values over time.

Figure 3

Contour plot illustrating the relationship between predicted rates of Visual Field Index (in %/year) change, intraocular pressure and corneal hysteresis measurements.