Corneal stiffness parameters predict progression in glaucoma suspect eyes

Disease progression is likely to occur in glaucoma suspect eyes with higher corneal stiffness parameters (SPs) and lower central corneal thickness (CCT), which are indicative of thin and stiff corneas, a recent study has found.

This prospective, longitudinal study examined corneal SPs as predictors of future progression in 371 eyes from 228 primary open-angle glaucoma suspects, based on optic disc appearance, with normal baseline Humphrey Visual Field (HVF) results.

The investigators measured baseline corneal SPs using Corvis ST and followed participants every 6 months with clinical examination, HVF testing, and optical coherence tomography (OCT). The baseline SP at first applanation (SP-A1) and highest concavity predicted the prospective outcome measures.

The investigators measured structural progression through the OCT rate of thinning of the retinal nerve fibre layer (RNFL) ang ganglion cell–inner plexiform layer (GCIPL). They also evaluated functional progression using permutation analysis of pointwise linear regression criteria on HVF testing.

SPs were positively associated with CCT. A higher SP-A1, which suggested a stiffer cornea, correlated 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) demonstrated faster RNFL thinning by 0.72 μm/year compared with eyes with lower SP-A1 and thicker CCT (95 percent confidence interval [CI], 0.17–1.28; p=0.011) and 2.9 times more likely to show fast RNFL progression of >1 μm/year (95 percent CI, 1.4–6.1; p=0.006). Results observed with GCIPL thinning were also consistent.

A higher SP-A1 also correlated with a higher risk of visual field progression (p=0.001), synergistic with thinner CCT (p=0.010). Eyes with higher SP-A1 and thinner CCT had 3.7-fold higher risk of visual field progression than eyes with thicker CCT and lower SP-A1 (95 percent CI, 1.3–10.5; p=0.014).

“Corneal SPs seem to act synergistically with CCT as risk factors for glaucoma progression,” the investigators said.