PREDICTING THE PERFORMANCE OF SIMULTANEOUS-VISION BIFOCAL CONTACT LENSES

Joy Martin

Abstract

PURPOSE. To test the hypothesis that variability in response to simultaneous vision contact lens correction is due in part to the aberrations of the individual wearing the contact lens.


METHOD. We simulated the performance of 3 bifocal contact lenses in 15 young and healthy subjects. The subjects' spectacle corrections were between +2.00 D and -2.00 D with no more than 0.50 D of astigmatism. The monochromatic aberrations of each eye were measured using a Shack-Hartmann
Wavefront Sensor and were fitted with a tenth-order Zernike polynomial. The optical aberrations of the bifocal contact lenses were mathematically
modeled and numerically added to the subject's own optical aberrations using custom software written in Matlab. The Strehl ratio, which is a
measure of the sharpness of the retinal image, was computed as a function of object distance for the unaccommodating eye.


RESULTS. For a 5 mm diameter pupil, 8 subjects experienced bifocality for all lens designs, 6 subjects had a mixed response, and one subject only experienced an increase in their depth of focus. In all cases, near vision was improved at the expense of a drop in Strehl ratio for distant viewing. The relative optical performance between distance and near vision depended on the particular lens design and the pupil size.


CONCLUSIONS. We show that the eye's optical aberrations could be a useful and important factor in predicting the success of wearing simultaneous vision bifocal contact lenses. Based on an aberration measurement, the specific lens design that is most suitable for the patient could be selected, or customized bifocal contact lenses could be designed that work specifically for each patient.

Details

Year: 2001

Program Number: 4:00 pm

Author Affiliation: University of Houston

Co-Authors: Austin Roorda

Co-Author Affiliation: University of Houston

Room: Room 114