Changes in Stress-Strain Index and Corneal Biomechanics in Granular Corneal Dystrophy.

Abstract

The aim of this study was to assess stress-strain index (SSI) and corneal biomechanical parameters in eyes with granular corneal dystrophy (GCD). This case-control study included 12 eyes of 12 patients with GCD (mean age 45.2 ± 18.7 years) and 20 eyes of 20 healthy individuals (mean age 54.4 ± 3.8 years). In addition to SSI, dynamic corneal response (DCR) parameters were assessed at the first and second applanation, including length (AL1, AL2), velocity (AV1, AV2), time (AT1, AT2), and deformation amplitude (DA A1, DA A2), and at the highest concavity (HC) phase, including DA, peak distance (PD), radius (HCR), and DA ratio (DAR 1 and 2 mm), by Corvis ST. Central corneal thickness (CCT) and biomechanically corrected intraocular pressure (bIOP) were considered covariates in comparing DCR parameters between the two groups. SSI was statistically significantly lower in eyes with GCD than in normal eyes (p = 0.04). The corneal velocity towards the first applanation was 0.02 m/s faster in the GCD eyes AV1 (0.15 ± 0.02 vs. 0.13 ± 0.02 m/s, p < 0.001) and IR (7.48 ± 1.01 vs. 6.80 ± 1.22 mm, p = 0.003) parameters were significantly higher in the GDC group, while AT1 (7.33 ± 0.66 vs. 7.47 ± 0.36 ms, p = 0.002) and HCR (7.42 ± 0.76 vs. 8.20 ± 1.08 mm, p = 0.014) were significantly lower in the normal group. GCD led to a change in biomechanical properties of the cornea. SSI refers to fewer stiff corneas in GDC than normal.