Abstract
Purpose: :
To explore the nature of a compensation mechanism between corneal and internal ocular aberrations using combined wavefront analysis and corneal topography in eyes with keratoconus.
Methods: :
The study comprised 43 eyes of patients with keratoconus and 41 control patients. Total ocular, corneal and internal wavefront measurements were provided by the NIDEK OPD-Scan II. Correlations between the individual corneal and internal aberrations were evaluated using correlation matrices in the two groups.
Results: :
Significantly higher corneal wavefront error (5.5±3.1µm) and internal (5.3±3.5) wavefront error aberrations were observed in eyes with keratoconus (p<0.001) compared to normals (corneal: 1.03±0.6, internal: 2.6±1.7). However, an increase in total ocular aberrations proportional to corneal and internal aberrations could not be observed in the keratoconus (4.5±2.39) and in the control (2.7±1.8) groups. Correlation matrix of corneal and internal ocular aberrations showed close negative correlation between corneal and internal vertical tilt (r=-0.96, p<0.001), oblique astigmatism (r=-0.83, p<0.001) and vertical coma (r=-0.95, p<0.001) in the keratoconus group. A similar, but less pronounced tendency could be observed in the control group: vertical tilt (r=-0.55, p<0.001), oblique astigmatism (r=-0.58, p<0.001) and vertical coma (r=-0.53, p<0.001).
Conclusions: :
A reducing effect of increased anterior corneal aberrations in keratoconic eyes is present, which is probably due to a compensation mechanism by internal optics.
Keywords: keratoconus • cornea: clinical science • optical properties