To determine if a difference exists in surgically-induced astigmatism (SIA) and the mean change in keratometric astigmatism in patients who underwent microcoaxial cataract surgery (MCCS).

A prospective study including 193 eyes with astigmatism of greater than 0.5 diopters was performed. The eyes were randomized into two groups: (1) 95 eyes with steep axis incision, and (2) 98 eyes with temporal incision. A 2.2-mm microcoaxial phacoemulsification was performed. The UCVA, BCVA and corneal topography (Orbscan II, Bausch & Lomb) were measured preoperatively and three months postoperatively. Surgically induced astigmatism was calculated via vector analysis, and the mean change in keratometric astigmatism was also calculated.

There were no significant differences in UCVA or BCVA between the two groups three months postoperative. The mean SIA was 0.45 ± 0.27 diopters in the steep axis incision group and 0.30 ± 0.17 diopters in the temporal incision group. In the steep axis incision group, the mean keratometric astigmatism showed a mean reduction of 0.31 ± 0.37 diopter (WTR: 0.37 D; oblique: 0.35D; ATR: 0.16 D), while the mean keratometric astigmatism showed a mean increase of 0.06 ± 0.29 diopters (WTR: 0.15 D increased; oblique: 0.11 D increased; ATR: 0.13 D reduced) in the temporal incision group. There were statistically significant differences in SIA and change in astigmatism between the two groups ( p = 0.002, p = 0.000).

In MCCS, steep axis incision achieved superior astigmatism correction in patients having with-the-rule or oblique astigmatism of greater than 0.5 diopters.