Association between surgically-induced astigmatism and cataract incision size in the early postoperative period

One hundred sixteen eyes with cataracts were prospectively randomized into four surgical groups. Silicone and polymethylmethacrylate (PMMA) intraocular lenses were implanted into the posterior chamber of these eyes through 4-, 6-, or 11-millimeter incisions by one surgeon. Surgically-induced astigmatism was evaluated in terms of: (1) the proportion of eyes achieving a refractive cylinder of 1.5 or less, without regard to axis; and (2) the induced cylinder, with regard to axis, using vector analysis. One week postoperatively, the eyes with a 4-millimeter incision had a significantly lower mean induced cylinder than those with larger incisions (P = .019); and all three phacoemulsification groups had a significantly higher proportion of eyes with a cylinder of 1.5 or less than the nuclear expression group (P < .01). One month postoperatively, the 4-millimeter-incision group had a significantly lower mean induced cylinder (P = .044) as well as a significantly higher proportion of eyes with a cylinder of 1.5 or less, than the larger-incision groups (P = .05). Three months postoperatively, no value of any parameter in any group differed significantly from that of that parameter in any other group.