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Kata Mihaltz, Illés Kovács, Zoltán Z. Nagy; Evidence of a Compensation Mechanism between Corneal and Internal Ocular Optical Aberrations in Patients with Keratoconus. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5166.
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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.
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.
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).
A reducing effect of increased anterior corneal aberrations in keratoconic eyes is present, which is probably due to a compensation mechanism by internal optics.
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