Aspheric IOLs diminish spherical aberrations but may compromise near vision, reading

J Cataract Refract Surg. 2009;35(4):663-671.

Issue: June 10, 2009

Aspheric IOL implantation markedly reduced spherical aberration and vertical coma, but the decrease in aberrations may have correlated with an undesirable reduction in depth of focus.

“The results in our study may imply that although asphericity of an IOL significantly improves mesopic contrast sensitivity, this may be at the expense of multifocality,” the study authors said, adding that reduced depth of focus may diminish near vision and hinder reading ability.

The prospective, randomized study included 94 eyes of 47 patients who received an AcrySof SN60WF aspheric IOL (Alcon) or an AcrySof SN60AT spherical in one eye and the other lens in the contralateral eye. Mean patient age was 71.7 years. Follow-up examinations were conducted at 3 months and 6 months.

Results showed no significant differences between the groups’ 100% and 9% logMAR best corrected visual acuity or photopic contrast sensitivity at any follow-up interval.

At 6 months, the aspheric IOL yielded 0.46 D less depth of focus than the spherical lens. The spherical IOL produced markedly more vertical coma and positive trefoil, which resulted in multifocality.

“This study opens further avenues for research in evaluating depth of focus and reading ability after aspherical IOL implantation,” the authors said.

This well-controlled study further validates earlier studies with the Tecnis aspheric IOL (Abbott Medical Optics). Aspheric optics deliver better mesopic contrast sensitivity. This is important to patients under challenging lighting conditions, such as driving at dusk. The disparity of vertical coma between the spheric and aspheric lens designs in this study is curious and unexplained. This may point the way to further studies on the alignment of the capsule and the pupil.

– Roger F. Steinert, MD
OSN Cornea/External Disease Board Member