Purpose: To compare the outcomes of coaxial microincision phacoemulsification with that of conventional coaxial phacoemulsificationSETTING: Department of Ophthalmology, Farabi and Noor Eye Hospitals, Tehran, IranMethods: In a prospective study, 74 eyes of 74 patients with cataract were randomly selected to have cataract extraction using 1 of 2 techniques: coaxial microincision phacoemulsification through a 2.2 mm incision (37 eyes) or conventional coaxial phacoemulsification through a 2.8 mm incision (37 eyes) and foldable intraocular lens (IOL) (SA60; Alcon) implantation. Intraoperative parameters were effective phacoemulsification time (EPT), surgical time, and total volume of balanced salt solution (BSS) used. Assessed ocular biometrics included corneal topography, to evaluate surgically induced astigmatism (SIA), as well as corneal thickness and endothelial cell count (ECC).Results: Using vectorial analysis the amount of SIA was 0.04±0.34 diopter (D) at 126.7 degrees in the 2.8 mm group and 0.07±0.49 D at 11.8 degrees in the 2.2 mm group, at one month postoperatively. At 3 months, the SIA was 0.06±0.41 D at 134.7 degrees and 0.10±0.62 at 161.4 degrees in the 2.8 mm and 2.2 mm groups, respectively.Conclusion: Although coaxial microincision cataract surgery (MICS) was a safe and effective technique there were no clinical or statistically significant differences between 2 techniques in minimizing the effect of incision size on SIA.