Abstract
Purpose: :
To investigate the feasibility of correcting higher order aberrations (HOA) in keratoconic eyes using customized soft contact lenses
Methods: :
Higher order aberrations up to the 10th Zernike order were measured using a Shack–Hartmann wavefront sensor for 3 keratoconic eyes wearing conventional prism ballasted soft contact lenses. Decentration in x and y directions and rotation relative to the pupil center were also measured simultaneously when contact lens position was stablized after blinks. Measured lens movement and aberrations for a 6mm pupil were used to design customized soft contact lenses which were manufactured using a lathing machine. Correction performance was assessed by measuring the residual aberration of the same 3 keratoconic eyes wearing the customized contact lenses. Variability in position of the customized lens between blinks was quantified to study the stability of correction.
Results: :
The average higher order rms wavefront error for the keratoconic eyes with the conventional and the customized contact lenses, was 2.88 ± 1.01 µm and 1.0 ± 0.24 µm, respectively. The HOA was reduced by a factor of 2.9 on average. The average variability in horizontal and vertical decentration and rotation of the customized lens between blinks was 29.3 µm, 79.0 µm and 1.3 degrees respectively. Variablitiy in residual higher order rms caused by lens movement was insignificant(average standard deviation on 3 eyes: 0.06 µm). Optical modulation transfer functions with the conventional and customized contact lenses were also calculated. Theoretical retinal image quality with customized lenses was improved by an average of 72% in contrast over conventional lenses. All 3 subjects reported significant subjective improvement in their vision.
Conclusions: :
The HOA in keratoconic eyes was successfully corrected using customized soft contact lenses. These lenses have the potential to provide substantial improvement of visual performance, especially in abnormal eyes, although the effect of other factors such as static lens decentration needs to be minimized for further improvement.
Keywords: contact lens • keratoconus