Long-term natural and modified course of surgically induced astigmatism after extracapsular cataract extraction.

A prospective study was carried out to investigate the long-term course of surgically induced astigmatism after extracapsular cataract extraction. Sixty-one eyes were followed for 36 months. In 27 eyes with post-operative astigmatism > 4D with-the-rule, one or two sutures were cut in the steeper meridian after 3 months. In another group of 34 eyes with only minor or no postoperative astigmatism with-the-rule, no suture was cut. We found that 1) postoperative astigmatism was significantly increased in all eyes after 1 week and 3 months, but decreased in time approaching preoperative values after 3 years, 2) surgically induced astigmatism was with-the-rule at 1 week and 3 months but turned against-the-rule in time in both groups. Astigmatism decay rate was significantly steeper in eyes with suture cutting, 3) the keratometric axis was exclusively with-the-rule after 1 week, but turned against-the-rule in both groups, approaching the preoperative distribution of axis after 3 years. We concluded that surgically induced astigmatism is a dynamic feature showing changes in size and axis even in the period 1-3 years postoperatively. Suture cutting seems to intensify the decrease in the induced astigmatism and accelerate the shift in astigmatic axis, turning astigmatism against-the-rule compared to eyes with intact sutures.