An objective and subjective comparative analysis of diffractive and front surface aspheric contact lens designs used...

As bifocal contact lenses have evolved, increasing emphasis has been placed on producing designs that are less dependent on such variables as pupil size and lens centration and movement. We evaluated these and other variables in 25 presbyopic patients who underwent consecutive 1-week trials, wearing two different contact lens types: a diffractive lens and a front surface aspheric lens. Distance and near visual acuities were not significantly reduced by either lens type, and both exhibited binocular summation. With each lens design, visual acuity remained relatively independent of pupil size and small degrees of lens decentration. Contact lens movement with the aspheric design was associated with subjective fluctuations in vision to a greater extent than with the diffractive design. Contrast sensitivity was also measured and found to be reduced with the diffractive lens but not significantly altered by the aspheric lens. Overall, only two patients could not be successfully fit with either lens type. After 6 months, 21 patients (84%) reported successful lens wear with their chosen lens type.