Effect of depth of the sclerocorneal incision on postoperative corneal astigmatism in manual small-incision cataract surgery

Purpose: To determine the effect of depth of scleral tunnel incision measured by anterior segment OCT on postoperative corneal astigmatism by comparing the change of magnitude of corneal astigmatism between superficial and deep sclerocorneal tunnel incision in manual small-incision cataract surgery (SICS). Methods: Depths of sclerocorneal incision of 72 eyes of patients undergoing uncomplicated manual SICS and attending regular follow-up schedule were assessed with anterior segment OCT at 6-week post-op follow-up. Results: The overall mean +/- standard deviation (SD) change of astigmatism for superficial incision, that is, <= 399 mu m, was 0.44 +/- 0.30 and that for deeper, that is, >= 400 mu m, was 0.13 +/- 0.48 and the change was significantly higher in <= 399 mu m group than in >= 400 mu m group (P = 0.003). In both superior and temporal incision locations, the mean +/- SD change of astigmatism for <= 399 mu m incision was 0.48 +/- 0.29 and 0.40 +/- 0.30, respectively, and that for >= 400 mu m was 0.03 +/- 0.34 and 0.23 +/- 0.57, respectively. The change of astigmatism was significantly higher in <= 399 mu m incision group overall (P = 0.003) and also higher in both superior and temporal incision location groups (P = 0.001 and P = 0.479, respectively). Conclusion: The depth of sclerocorneal incision had a statistically significant effect on the change of astigmatism following manual SICS, with superficial incision (<= 399 mu m) causing a higher change than deeper incision (>= 400 mu m).