Abstract
Purpose:
The CorvisST (Oculus) and Reicherts Ocular Response analyzer (ORA) provide in vivo measures of corneal biomechanics. It is likely that the structure of the ocular globe affects the biomechanics. The study assesses the association between corneal biomechanics using CorvisST and ORA and theirs with axial length (AL), refractive error and central corneal thickness (CCT) in healthy eyes
Methods:
Corneal biomechanics was assessed in 43 healthy adults (18-40 yrs (25.2±7.0); 81% female, 19% male) with CorvisST and ORA. The biomechanics of both eyes were evaluated randomized. Measures of length (L), time (T) of the applanation point 1 (A1) and 2 (A2) and the highest concavity (HC) were determined with CorvisST. The ORA provided measures of corneal hysteresis (CH) and corneal resistance factor (CRF). Refractive error [MSE (D)] and AL were measured using cycloplegic autorefraction and the Haag Streit LenStar. CCT was determined with Pentacam (Oculus). Subjects were grouped according to MSE (D): myopic (<-0.50) -2.96+/-1.99, AL 24.82+/-1.05mm, n=18; non-myopic (≥-0.50) +0.80+/-1.23, AL 23.27+/-0.90mm, n=23. To evaluate the relationship between MSE, AL and biomechanics a multivariate variance analysis was conducted, using CCT and age as covariates. Correlation coefficient was calculated CCT and age-adjusted
Results:
Mean CCT was 559+/-37µm, CRF 13.0+/-11.6, CH 13.6+/-12.7, A1T 7.12+/-0.25sec, A1L 1.79+/-0.04mm, A2T 21.98+/-1.49sec, A2L 1.70+/-0.35mm and HC 16.71+/-0.61mm. Significant correlation was found between MSE and AL (r=-0.826, p<0.001). No significant effect of MSE was found for CorvisST and ORA metrics. When assessing the groups separately, no significant (p>0.05) correlation was found between corneal biomechanics and MSE and AL (p>0.05) for the myopics. In the non-myopic group a positive association was identified between AL and CRF (r=0.458, p=0.049), CH (r=0.457, p=0.049) and A1L (r=0.456, p=0.013) whilst AL and HC were found to be negatively correlated (r=-0.487, p=0.036)
Conclusions:
The study demonstrates significant correspondence between corneal biomechanics parameters derived from CorvisST and ORA and AL in non-myopics. The results have interesting implications on the role of corneal biomechanics in MSE development. Further investigation into the relationship between biometric and corneal biomechanical properties in keratoconus, refractive surgery and juvenile myopia is required.