Surgically induced astigmatism in phacoemulsification, pars plana vitrectomy, and combined phacoemulsification and vitrectomy: a comparative study.

ABSTRACT

PURPOSE: To study the surgically induced astigmatism (SIA) in combined phacoemulsification and vitrectomy, and compare with that when either procedure is performed alone. METHODS: This is a prospective comparative interventional trial comprising of 60 eyes of 60 consecutive patients with cataract and/or vitreo-retinal pathology. They were divided equally into three groups based on the type of procedure Group A, phacoemulsification alone group, using a 3.0-3.2 mm wide unsutured sclero-corneal tunnel incision at 1.0 mm post-limbus at 10 o'clock; Group B, par plana vitrectomy alone group, using three sclerotomies at 3.5 mm post-limbus at 2, 8, and 10 o'clock (right eye) or at 2, 4, and 10 o'clock (left eye) positions; and Group C, combined phacoemulsification and pars plana vitrectomy group. Main outcome measures were the amplitude (K-induced) and the axis of SIA calculated by rectangular coordinate method using the Holladay-Cravy-Koch formula. RESULTS: The mean K-induced amplitudes were 0.19+/-0.14 D, 0.17+/-0.11 D, and 0.23+/-0.19 D for groups A, B, and C, respectively. The range of K-induced amplitudes for the entire cohort was 0.00-0.77 D. No overall statistically significant differences in the pre- and postoperative topographic astigmatism amplitudes and the K-induced between groups A, B, and C were found (all P>0.05). Minor shifts, of doubtful clinical significance, in the axes of SIA were present. CONCLUSIONS: Combined phacoemulsification and pars plana vitrectomy does not induce significant astigmatic change per se, and its amount is similar to that when either procedure is performed alone.