Prospective evaluation of surgically induced astigmatism and astigmatic keratotomy effects of various self-sealing small incisions.

The refractive effects of self-sealing clear corneal and corneoscleral tunnel incisions, 3.5 mm and 5.2 mm, in cataract surgery were studied prospectively by automatic keratometric evaluation at day one postoperatively and weeks one, three, and six. Keratometric readings were converted to polar values. The amount of surgically induced astigmatism was calculated for each incision and mean postoperative keratometric astigmatism was estimated for patients with preoperative against-the-rule and with-the-rule astigmatism to evaluate the astigmatic keratotomy effects of the incisions. The corneoscleral incisions were almost astigmatically neutral, with no major difference between the 3.5 mm and the 5.2 mm incisions after six weeks. The 5.2 mm frown incisions were less stable than the straight corneoscleral incisions. Clear corneal incisions resulted in a considerable amount of induced astigmatism; there was more with the 5.2 mm incisions than with the 3.5 mm incisions. Temporal incisions resulted in a with-the-rule induced change and superior incisions, an against-the-rule induced change. The refractive effect of the clear corneal incisions did not change significantly from day one to week six. The astigmatic keratotomy effects of these incisions were therefore more useful and predictable. Preoperative against-the-rule astigmatism was reduced significantly by temporally placed clear corneal incisions and preoperative with-the-rule astigmatism, by superiorly placed clear corneal incisions. If one considers the preoperative astigmatism when selecting incision type and location for small incision cataract surgery, one can minimize postoperative keratometric astigmatism.