RESUMO
PURPOSE: To evaluate the factors that affect postoperative astigmatism and post-suture removal astigmatism, and to evaluate the risk factors associated with astigmatism axis shift. METHODS: We performed a retrospective chart review of 130 eyes that had undergone uneventful phacoemulsification cataract surgery. Preoperative astigmatism was divided into four groups (Groups I, II, III, and IV) according to the differences between the axis of preoperative astigmatism (flattest axis) and the incision axis (105 degrees). We analyzed the magnitude and axis of the induced astigmatism after the operation and after suture removal in each group. We also analyzed the factors which affected the postoperative astigmatism and post-suture removal astigmatism in each sub-group of Groups I, II, III, and IV, excluding postoperative or post-suture removal axis shift (specifically, Group I(WAS), II(WAS), III(WAS), and IV(WAS)). We identified the variables associated with the prevalence of postoperative astigmatism axis shift and those associated with the prevalence of post-suture removal axis shift. RESULTS: An increase in the magnitude of postoperative astigmatism was associated with an increase in the preoperative magnitude of astigmatism in Groups I(WAS), II(WAS), and III(WAS) (p<0.05), and with an increase in the corneal tunnel length in Group I(WAS). A decrease in the magnitude of postoperative astigmatism was associated with an increase in the corneal tunnel length in Groups III(WAS) and IV(WAS) (p<0.05). An increase in the magnitude of post-suture removal astigmatism was associated with an increase in the magnitude of postoperative astigmatism in Groups I(WAS) and IV(WAS) (p<0.05), and with late suture removal in Group IV(WAS) (p<0.05). A decrease in the magnitude of post-suture removal astigmatism was associated with late suture removal in Groups I(WAS) and II(WAS). A logistic regression analysis showed that the prevalence of post-suture removal astigmatism axis shift was associated with increased corneal tunnel length, decreased magnitude of postoperative astigmatism, and early suture removal. CONCLUSIONS: In order to reduce postoperative and post-suture removal astigmatism, we recommend a short corneal tunnel length and late suture removal in patients with Group I(WAS) characteristics, late suture removal in Group II(WAS)-like patients, long corneal tunnel length in Group III(WAS)-like patients, and long corneal tunnel length and early suture removal in patients with characteristics of Group IV(WAS).