A total of 81 consecutive keratoconic eyes of 81 patients ranging in age from 11 to 58 years were included in this study. Three groups were differentiated according to the severity of keratoconus: mild (37 eyes), moderate (24 eyes) and severe keratoconus (20 eyes). Visual acuity, refraction, corneal topography and corneal aberrations were evaluated. Additionally, corneal biomechanics was analyzed with the ORA system by means of 2 parameters: corneal hysteresis (CH) and corneal resistance factor (CRF). Correlations between biomechanical and the remaining clinical parameters were investigated......CH and CRF values in the severe keratoconus group were significantly lower than those found in the other two groups (p
0.01). A significant difference in the CRF was found between mild and moderate cases (p=0.04). A moderate correlation was found between the CRF and mean keratometry in the overall sample (r=-0.564). Additionally, a significant strong correlation was found between the spherical-like root mean square (RMS) and the CRF only in the severe keratoconus group (r=-0.655). Multiple regression analysis revealed that CRF was significantly correlated with keratometry and the corneal spherical-like RMS (R2=0.40, p<0.01).
CONCLUSIONS: The ORA corneal resistance factor is in relation with the magnitude of corneal spherical-like aberrations, especially in severe keratoconus. It should be considered as an additional factor for keratoconus grading.
