Association between corneal biomechanical properties and glaucoma severity

Abstract

Purpose: To investigate the association between corneal biomechanical parameters using the Ocular Response Analyzer (ORA) and glaucoma severity.

Design: Observational cross-sectional study.

Methods: Two hundred ninety-nine eyes of 191 patients with confirmed or suspect glaucoma were recruited at the University of California, San Diego. Corneal hysteresis (CH) and corneal resistance factor (CRF) were obtained from all participants. Standard automated perimetry was done using the 24-2 Swedish Interactive Threshold Algorithm. Retinal nerve fiber layer (RNFL) thickness measurements were obtained using GDx ECC and spectral-domain optical coherence tomography (SD-OCT). The association between ORA parameters and disease severity was evaluated using univariable and multivariable regression models.

Results: CH and CRF were both positively associated with mean defect (MD) (R(2) = 0.03; P < .01 and R(2) = 0.10; P < .01, respectively). In multivariable analysis, the association between CRF and MD remained significant while CH to MD did not (P < .01 and P = .77). In the GDx ECC subgroup (204 eyes), there was a weak association between CH and CRF and average RNFL thickness (R(2) = 0.07; P < .01 and R(2) = 0.05; P < .01, respectively), which was not observed in the SD-OCT subgroup (146 eyes) (R(2) = 0.01; P = .30 and R(2) = 0.01; P = .21). After adjusting for central corneal thickness, age, and axial length, the relationship of CH and CRF to RNFL thickness no longer reached statistical significance.

Conclusions: The current study found only a weak relationship between corneal biomechanical parameters and measures of structural and functional damage in glaucoma.

Trial registration: ClinicalTrials.gov NCT00221897.

Figure 1. Association of corneal hysteresis and corneal resistance factor and visual field

Scatterplots with locally weighted smoothing (LOWESS) of corneal hysteresis (CH) (a) and corneal resistance factor (CRF) (b), as measured by the Ocular Response Analyser, and visual field mean defect (MD).

Figure 1. Association of corneal hysteresis and corneal resistance factor and visual field

Scatterplots with locally weighted smoothing (LOWESS) of corneal hysteresis (CH) (a) and corneal resistance factor (CRF) (b), as measured by the Ocular Response Analyser, and visual field mean defect (MD).

Figure 2. Association of corneal hysteresis and corneal resistance factor and SDOCT

Scatterplots with locally weighted smoothing (LOWESS) of corneal hysteresis (CH) (a) and corneal resistance factor (CRF) (b), as measured by the Ocular Response Analyser, and average RNFL thickness, as measured by SDOCT.

Figure 2. Association of corneal hysteresis and corneal resistance factor and SDOCT

Scatterplots with locally weighted smoothing (LOWESS) of corneal hysteresis (CH) (a) and corneal resistance factor (CRF) (b), as measured by the Ocular Response Analyser, and average RNFL thickness, as measured by SDOCT.

Figure 3. Association of corneal hysteresis and corneal resistance factor and GDxECC

Scatterplots with locally weighted smoothing (LOWESS) of corneal hysteresis (CH) (a) and corneal resistance factor (CRF) (b), as measured by the Ocular Response Analyser, and average RNFL thickness, as measured by GDxECC.

Figure 3. Association of corneal hysteresis and corneal resistance factor and GDxECC

Scatterplots with locally weighted smoothing (LOWESS) of corneal hysteresis (CH) (a) and corneal resistance factor (CRF) (b), as measured by the Ocular Response Analyser, and average RNFL thickness, as measured by GDxECC.