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Z. Schlegel, Y. Lteif, D. Gatinel; Evaluation of Total, Corneal and Internal Ocular Optical Aberrations in Patients With Keratoconus. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4344. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To compare the internal, corneal and total ocular aberrations using wave front analysis combined with corneal topography in normal and keratoconic eyes.
OPD-Scan combined topography and aberrometer (NIDEK) was used to measure the optical aberrations of 62 eyes (36 patients) with keratoconus (keratoconus group) and 144 normal myopic eyes (normal group). We compared the Root Mean Square (RMS) coefficient values of total, corneal and internal aberrations to the 6th order, measured for 5 mm of corneal and pupillary diameters and divided in 7 groups: Tilt, High Order Total, Total Coma, Total Trefoil, Total QuadraFoil, Total Spherical, and Total High Order Astigmatism. The differences between were statistically analyzed. A p value less than 0.05 was considered statistically significant.
High order total ocular aberrations showed statistically significant differences between the keratoconus group and normal group, with RMS of 1.09 µm ± 0.58 (SD) and 0.29 ± 0.30 µm (p<10-5) respectively. These differences was particularly significant in corneal aberrations with RMS of Tilt, High Order Total, Total Coma, Total Trefoil, Total QuadraFoil, Total Spherical, and Total High Order Astigmatism of 3.83±2.72µm, 1.63±0.96µm, 1.34±0.93µm, 0.58±0.37µm, 0.21±0.19µm, 0.33±0.31µm, 0.28±0.21µm respectively in the keratoconus group, and 0.35 ±0.27µm, 0.27±0.28µm, 0.14±0.13µm, 0.12±0.131µm, 0.06± 0.13µm, 0.14± 0.10µm, 0.05 ±0.11µm respectively in the normal group (p<10-6). For each group of aberrations except for the Total Trefoil, the magnitude of total ocular aberrations was proportionally lower than the corneal compound indicating some reducing effect of internal aberrations vis-à-vis of corneal aberrations. The internal aberrations in the keratoconus group were higher than in the normal group for all 7 aberrations examined.
There was an increased compensatory effect of increased corneal aberrations by internal aberrations in keratoconic eyes. The exact mechanisms for this compensation are yet to be elucidated.
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