Comparison of higher order aberrations in eyes with aspherical or spherical intraocular lenses

To compare ocular, internal, corneal aberrations, and contrast sensitivity in patients implanted with aspheric or spherical intraocular lenses (IOLs).

Total, corneal, and internal aberrations were measured using ray-tracing technology in 23 eyes implanted with aspheric (Tecnis ZA9003) IOLs, and in 25 eyes implanted with spherical (AcrySof SA60AT) IOLs. Spherical aberration (SA), coma, trefoil, and RMS of higher order aberrations (HOAs) were analysed for 4.0 and 6.0 mm optical zones. Best-corrected visual acuities (BCVAs), contrast sensitivity under photopic and mesopic conditions, and modulation transfer function (MTF) were evaluated to compare visual performances.

The mean internal SA was -0.06/-0.35 microm in the aspheric IOL group and 0.04/0.17 microm in the spherical IOL group (at 4 mm/6 mm pupil). Total SA was near to zero in the aspheric IOL group, and was 0.11+/-0.034/0.48+/-0.13 microm in the spherical IOL group. The internal Z(3)(-1) and total Z(3)(-1) were more negative in the spherical IOL group. The internal Z(3)(-3) was more negative in the aspheric IOL group. The two groups were similar in terms of other Zernike values and RMS of HOA. There were no differences in BCVA between groups. The aspheric IOL group showed better contrast sensitivity at 3-6 cpd in photopic and 1.5-6 cpd in mesopic conditions. The MTF curve was better for the aspheric IOL group at 5-10 cpd.

The aspheric IOL with a negative SA reduced total SA by compensating for positive corneal SA. These effects resulted in improved contrast sensitivity.