Intraocular Pressure and CCT in Biomechanical Assessment of Normal and Keratoconic Corneas
Purpose
To evaluate the effect of IOP and CCT on biomechanical indices of normal and keratoconic patients.
Methods
One eye randomly selected from 98 patients with clinical bilateral keratoconus and from 301 patients with normal corneas were retrospectively analyzed. All eyes were examined by noncontact Scheimpflug-based tonometer (Corvis ST) and Pentacam HR (Oculus, Wetzlar, Germany). Spearman correlation coefficients were calculated to assess the correlation between Corvis biomechanical parameters with IOP and central corneal thickness (CCT).
Results
The Corvis provides 34 biomechanical parameters of corneal deformation response. In keratoconic eyes, 15 of these parameters had shown no statistically significant correlation with IOP and 17 with CCT (p>0.05). In normal eyes, 10 of these parameters had shown no statistically significant correlation with IOP and 9 with CCT (p>0.05). The time to reach the maximum amplitude of deflection was non correlated to IOP or CCT in both groups. The first and second applanation’s amplitude of deformation weren’t correlated to IOP and CCT in keratoconus group. In normal group only the second applanation’s amplitude of deformation was not correlated to IOP and CCT.
Conclusion
There is a strong influence of IOP and CCT on corneal deformation response in normal and keratoconic eyes. However, some parameters assessed by the Corvis ST seem to be more IOP and CCT independent.