LAUSR

OBJECTIVE To investigate corneal stiffness parameters as predictors of future progression risk in glaucoma suspect eyes. DESIGN Prospective longitudinal study. PARTICIPANTS 371 eyes from 228 primary open angle glaucoma suspects, based on the optic disc appearance, with a normal baseline Humphrey Visual Field (HVF). METHODS Baseline corneal stiffness parameters were measured using Corvis ST. Participants were followed up 6-monthly with clinical examination, HVF testing, and optical coherence tomography (OCT). We used the baseline stiffness parameter at first applanation (SP-A1) and highest concavity in predicting the prospective outcome measures. MAIN OUTCOME MEASURES Structural progression was measured by the OCT rate of thinning of the retinal nerve fibre layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL). Functional progression was assessed by permutation analysis of pointwise linear regression criteria on HVF testing. RESULTS Stiffness parameters correlated positively with central corneal thickness (CCT), which was adjusted for in all analyses. A higher SP-A1, suggestive of a stiffer cornea, was associated with a faster rate of RNFL thinning (P<0.001), synergistic with thinner CCT (P=0.004) over a mean follow-up of 4.2 years. Eyes with higher SP-A1 and thinner CCT (thin and stiff corneas) had an accelerated RNFL thinning by 0.72 μm/year relative to eyes with lower SP-A1 and thicker CCT (95% confidence interval [CI] 0.17-1.28; P=0.011), and were at 2.9-fold higher likelihood of fast RNFL progression of >1 μm/year (95% CI 1.4-6.1; P=0.006). Consistent results were also observed with GCIPL thinning. Furthermore, a higher SP-A1 was associated with a greater risk of visual field progression (P=0.002), synergistic with thinner CCT (P=0.010). Eyes with higher SP-A1 and thinner CCT were at 3.7-fold greater risk of visual field progression relative to eyes with thicker CCT and lower SP-A1 (95% CI 1.3-10.5; P=0.014). CONCLUSION Glaucoma suspect eyes with higher corneal stiffness parameters and lower CCT, suggestive of thin and stiff corneas, are at greater risk of progression. Corneal stiffness parameters appear to act synergistically with CCT as risk factors for glaucoma progression.