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P.S. Kollbaum, S. Mathews, L.N. Thibos, A. Bradley; Diurnal Fluctuations in Ocular Aberrations in Keratoconus . Invest. Ophthalmol. Vis. Sci. 2003;44(13):4070.
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Purpose: This experiment examined the impact of gas permeable (GP) contact lenses on the monochromatic aberrations of keratoconic eyes. We also determined the stability of these aberrations throughout the day. Methods: Five aberration measurements (COAS Wavefront Science Inc.) were taken in the early morning, at midday, and in the evening on ten eyes of five diagnosed keratoconic subjects. Measurements were taken with and without habitual GP contact lens correction. Data were analyzed for a 5mm pupil diameter. Results: As expected, these keratoconic subjects possessed significant lower order aberrations (defocus and astigmatism), which were significantly decreased with the GP correction, although clinically significant residual astigmatism was often observed. Unlike normal eyes, the uncorrected keratoconic eyes generally exhibited negative spherical aberration (mean = -0.10 microns), and in every case, GP correction converted this to positive SA (mean = 0.29). GP correction reduced levels of both vertical and horizontal coma in most eyes. One unexpected result of GP correction was that the diurnal fluctuations in higher order aberrations were reduced by a factor of about 2. Conclusions: In addition to the impact on defocus and astigmatism, we find that GP correction of keratoconic eyes also has a significant impact on their higher order aberrations. Gas permeable contact lenses also improve the stability of these higher order aberrations, which is a prerequisite for any attempt at correction.
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