Spherical aberration in relation to visual performance in contact lens wear.

INTRODUCTION: The aim of the present study was to evaluate changes in spherical aberration and their effect on visual quality (visual acuity and contrast sensitivity) in both distance and near with different non-custom-made contact lenses. METHODS: A wavefront analyser was used to measure the aberrations in each subject's eyes uncorrected and with the contact lenses: a standard lens and two aspherical contact lenses. High-contrast visual acuity at distance was measured with Test-Chart 2000 (100% contrast) and at near with Sloan ETDRS Near Point chart (100% contrast). Low-contrast visual acuity at distance was measured with Test-Chart 2000 (10% contrast) and contrast measurements at near with Mars letter contrast sensitivity chart. RESULTS: Mean spherical aberration was positive for all pupil sizes in the uncorrected eye, residual spherical aberration was close to zero with the standard lens for all pupil sizes, whereas the two aspheric contact lenses over-corrected spherical aberration. The changes in aberration were statistically significant (p < 0.05) with all lenses. No significant difference could be detected between trial frame correction, spherical and aspherical soft contact lens designs with respect to visual quality. This was the case for both distance and near. CONCLUSION: The results are in line with previous studies and indicate that non-custom-made spherical aberration control contact lenses have little effect on visual quality as defined in this study.

Spherical aberration in contact lens wear.

INTRODUCTION: The aim of the present studies was to investigate the effect on spherical aberration of different non custom-made contact lenses, both with and without aberration control. METHODS: A wavefront analyser (Zywave, Bausch & Lomb) was used to measure the aberrations in each subject's right eye uncorrected and with the different contact lenses. The first study evaluated residual spherical aberration with a standard lens (Focus Dailies Disposable, Ciba Vision) and with an aberration controlled contact lens (ACCL) (Definition AC, Optical Connection Inc.). The second study evaluated the residual spherical aberrations with a monthly disposable silicone hydrogel lens with aberration reduction (PureVision, Bausch & Lomb). RESULTS: Uncorrected spherical aberration was positive for all pupil sizes in both studies. In the first study, residual spherical aberration was close to zero with the standard lens for all pupil sizes whereas the ACCL over-corrected spherical aberration. The results of the second study showed that the monthly disposable lens also over-corrected the aberration making it negative. The changes in aberration were statistically significant (p<0.05) with all lenses. CONCLUSION: Since the amount of aberration varies individually we suggest that aberrations should be measured with lenses on the eye if the aim is to change spherical aberration in a certain direction.