FACTORS INFLUENCING POSTOPERATIVE ASTIGMA TISM IN NO-STITCH CATARACT-SURGERY

Background: One of the main advantages of the no-stitch technique in c ataract surgery is that induced astigmatism occurs less frequently tha n with any other procedure and stabilizes within a very short time pos toperatively. The resultant high wound strength enabled us to alter th e incision parameters in an attempt to indentify those which influence d postoperative astigmatism, the ultimate goal being to improve the pr ognosis of the expected astigmatism. Since the influence of tunnel wid th and incision length and shape were well known,we investigated the i nfluence of incision depth and site and that of various parameters in a prospective randomized and controlled clinical trial. Methods: The s tudy included 256 eyes with a 7-mm tunnel incision as examined in 256 patients. The following subgroups of 27 eyes each were investigated: p rimary incision depth of 300 mu m versus 500 mu m, limbal incision ver sus scleral incision,scleral incision in the 12 o'clock position versu s temporal scleral incision,and limbal incision in the 12 o'clock posi tion versus temporal limbal incision. In another group the influence o f age, IOP, axial length of the globe, preoperative astigmatism, corne al diameter, and postoperative astigmatism as measured by the keratome ter were all assessed using Spearman's correlation coefficient. Result s: Temporal incisions made 2 mm posterior to the limbus resulted in in duced astigmatism of 0.64 +/- 0.22 D 6 months postoperatively, which w as less than after incisions in the 12 o'clock position (0.98 +/- 0.40 D). Induced astigmatism was highest after limbal incisions in the 12 o'clock position (1.31 +/- 0.60 D), yet was less if a temporal limbal incision was made (0.84 +/- 0.52 D). Incision depth did not have signi ficant influence on induced astigmatism. Of the parameters, age (Spear mean's correlation coefficient after 4 weeks 0.34; P = 0.002; after 6 months 0.28; P = 0.01), and preoperative astigmatism (Spearman's corre lation coefficient after 4 weeks 0.28; P = 0.01; after 6 months 0.27; P = 0.01) had a significant influence on postoperative astigmatism. Co nclusions: These findings indicate that induced astigmatism was highes t after limbal incisions in the 12 o'clock position and lowest after s cleral incisions in the temporal position. Age and preoperative astigm atism were also found to influence induced astigmatism significantly. All of these factors have to taken into account to minimize postoperat ive astigmatism.