Induced astigmatism with 2.2- and 3.0-mm coaxial phacoemulsification incisions

To evaluate the difference between 2.2-mm incision micro-coaxial phacoemulsification and traditional 3.0-mm coaxial phacoemulsification with respect to surgically induced astigmatism after temporally oriented clear corneal incision cataract surgery.

This prospective, randomized, intra-patient controlled study comprised 22 patients who underwent clear corneal cataract surgery in both eyes. One eye received 2.2-mm incision micro-coaxial phacoemulsification with intraocular lens (IOL) implantation and the fellow eye received traditional 3.0-mm coaxial incision phacoemulsification with IOL implantation. The 2.2-mm incisions were created with a diamond keratome after a 200-microm groove was constructed in clear cornea at the temporal limbus. The 3.0-mm incisions were created without a pre-cut groove, using a metal keratome. All cases were uncomplicated. Pre- and postoperative keratometric astigmatism at 6 weeks was measured using a hand held Nikon Retinomax K-plus 2 Autorefractor. Three methods were used to analyze the surgically induced astigmatism (SIA) data: 1) algebraic analysis of the magnitude of keratometric astigmatism induced by the surgery, 2) magnitude of SIA by vector analysis, and 3) aggregate analysis of astigmatism using vector analysis.

The mean change in the magnitude of keratometric astigmatism was 0.10+/-0.08 diopters (D) with the 2.2-mm micro-coaxial incisions and 0.32+/-0.20 D with the 3.0-mm traditional incisions (P=.0002). Usingvector analysis, the mean magnitude of SIA was 0.35+/-0.21 D with the 2.2-mm incisions and 0.67+/-0.48 D (P=.006) with the 3.0-mm incisions.

Surgically induced astigmatism with 2.2-mm micro-coaxial incisions and traditional 3.0-mm clear corneal incisions with intra-patient control resulted in statistically and clinically significant reduction in surgically induced astigmatism with the smaller incision size.