The long-term decay of surgically induced corneal astigmatism following planned extracapsular cataract extraction has been studied in 395 patients who had limbal or scleral pocket incisions of 60 to 140 degrees. Limbal incisions were closed with a full-thickness shoelace closure; scleral pocket incisions, with a new, modified shoelace closure. Suture material was 10-0 nylon, 9-0 nylon, 10-0 polypropylene (Prolene), and 10-0 polyester (Mersilene). The nylon sutures demonstrated clinically significant hydrolysis beginning at five months (10-0) and 12 months (9-0). Because of the adverse hydrolytic effects, 10-0 nylon was eliminated from the scleral pocket closure group. The hydrolysis of 9-0 nylon caused excessive late astigmatic changes in patients who did not heal normally. Prolene and Mersilene showed no tendency toward hydrolysis; however, the elasticity of Prolene produced more against-the-rule change in astigmatism than desired even though it was stable over the long run. I stopped using nylon sutures in cataract (and keratoplasty) wound closures and switched to routine use of Mersilene.