Control of corneal astigmatism following cataract extraction by selective suture cutting

We evaluated the ability of selective suture cutting to reduce postoperative corneal astigmatism in 75 eyes of 68 patients who underwent extracapsular cataract extraction with posterior chamber intraocular lens implantation. Keratometric and refractive measurements were obtained before and at selected intervals (3, 6, 10, 26, and 52 weeks) after surgery. The number of sutures cut during the sixth week after surgery was based on the degree of astigmatism (0.00 to 2.00 diopters (D), no sutures cut; 2.25 to 3.00 D, one suture cut; 3.25 to 4.00 D, two sutures cut; greater than or equal to 4.25 D, three sutures cut). Our analysis demonstrated the following: (1) a spontaneous reduction of 0.5 D in surgically induced astigmatism in eyes without suture cutting, (2) an additional reduction of 1.2 D in postoperative astigmatism for each suture cut, and (3) attainment of 75% to 93% of the total effect of suture cutting within four weeks. The final astigmatism one year after surgery had increased by a mean of 0.9 D, exhibited predominantly with-the-rule properties, and showed no significant difference among the four groups of patients. Vector analysis revealed that only small shifts in the axis of astigmatism occurred after suture cutting. A strong correlation between the keratometric and subjective refractive measurements during all postoperative examinations indicated that corneal astigmatism is primarily responsible for postoperative astigmatism.