Higher corneal stiffness parameters and lower central corneal thickness are associated with greater risk of glaucoma progression in glaucoma suspect eyes, appearing to work together, a study published in Ophthalmology shows.
The prospective longitudinal study focuses on corneal stiffness parameters’ ability to predict future progression risk. The investigation took into account 371 eyes of 228 primary open-angle glaucoma suspects. Researchers measured baseline corneal stiffness parameters with a novel non-contact biomechanical measurement device. Patients returned for follow-up visits every 6 when they were monitored with a clinical exam,visual field testing, and optical coherence tomography (OCT). They used baseline corneal stiffness parameters at first applanation (SP-A1) and highest concavity to predict prospective outcome measures. OCT rate of thinning of the retinal nerve fiber layer (RNFL) and ganglion cell–inner plexiform layer (GC-IPL) measured structural progression, while permutation analysis of pointwise linear regression criteria on visual field testing assed functional progression.
They found a positive correlation with stiffness parameters and central corneal thickness (CCT) (which they adjusted for in all analyses). Having a higher SP-A1 — which could indicate a stiffer cornea — was associated with RNFL thinning (P <.001). It was also “synergistic with thinner CCT” (P =.004) during a mean follow-up of 4.2 years. Eyes with higher SP-A1 and thinner CCT with thin and stiff corneas meant faster 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 =.011) and were at 2.9-fold higher likelihood of fast RNFL progression of more than 1 μm/year (95% CI, 1.4–6.1; P =.006),” the study says. They found consistent results with GCIPL thinning.
In addition, that higher SP-A1 was associated with greater risk of visual field progression (P =.002), again synergistic with thinner CCT (P =.010). Those eyes also had a 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 =.014).
The study’s limitations include that clinicians treated patients at their discretion, which could have slowed or delayed progression outcomes. While investigators demonstrated that eyes treated with topical glaucoma medications did not have a significant difference in stiffness parameters compared to treatment-naïve eyes, they did not perform non-contact biomechanical measurements before and after using topical medications to better assess the relationship.
Qassim A, Mullany S, Abedi F, et al. Corneal stiffness parameters are predictive of structural and functional progression in glaucoma suspects. Ophthalmol. Published online November 24, 2020. doi:10.1016/j.ophtha.2020.11.021