Corneal aberrations before and after small-incision cataract surgery

To study the effect of small-incision cataract surgery on the optical aberrations of the cornea.

Corneal topography was measured before and after cataract surgery on 70 eyes of 70 patients. Monofocal foldable IOLs were implanted after phacoemulsification through a clear-cornea, 3.5-mm incision without suture. Corneal aberrations, up to the fifth order and 6-mm pupil, were calculated by ray-tracing from the corneal topography. Pre- and postoperative aberrations were compared in each patient and the optical changes induced by surgery investigated.

The root mean square of the wave aberration slightly increased on average after surgery (pre, 0.65 +/- 0.46 microm; post, 0.85 +/- 0.63 microm). Most aberration terms were similar, averaged across the 70 patients, before and after surgery (spherical aberration: pre, 0.32 +/- 0.12 microm, and post, 0.34 +/- 0.19 microm; astigmatism: pre, 0.9 +/- 0.8 D, and post, 1.1 +/- 1.0 D; coma: pre, 0.27 +/- 0.18 microm, and post, 0.32 +/- 0.33 microm). However, in each patient, there were changes after surgery in the magnitude (either increasing or decreasing) and/or orientation of aberrations. The mean induced astigmatism was -1.0 +/- 0.9 D at the orientation of the surgical meridian. Induced trefoil also showed a predominant pattern at this direction. Patients with nasal incisions experienced larger changes.

Small-incision surgery does not systematically degrade the optical quality of the anterior corneal surface. However, it introduces changes in some aberrations, especially in nonrotationally symmetric terms such as astigmatism, coma, and trefoil. The incision site plays a main role in the corneal changes after surgery.