Topographic analysis of early changes in corneal astigmatism after cataract surgery.

Using the Topographic Modeling System (TMS), we studied the early changes in anterior corneal curvature following cataract surgery. Thirty patients who had planned extracapsular cataract extraction (p-ECCE) or phacoemulsification were evaluated with TMS at three days, and one, two, three, and five weeks postoperatively. After p-ECCE, the upper part of the cornea which corresponded to the wound and the lower cornea markedly steepened and showed a bow-tie pattern of astigmatism. Eight (57%) of 14 cases showed little reduction in the corneal steepening at five weeks postoperatively. In five cases (36%) the steepening in the lower cornea was less than the minimal change in the upper cornea. After phacoemulsification, corneal steepening was much less than it was after p-ECCE; three cases (17%) showed almost no surgically induced alteration of the cornea. In eight phacoemulsification cases (61%), postoperative corneal steepening decreased rapidly and the corneal shape recovered within five weeks. Our topographic analysis clearly demonstrated that a smaller wound in phacoemulsification surgery produced less corneal steepening and stabilized more rapidly than a larger wound in p-ECCE.