Surgically induced astigmatism in combined phacoemulsification and vitrectomy; 23-gauge transconjunctival sutureless vitrectomy versus 20-gauge standard vitrectomy

Background: To study the surgically induced astigmatism (SIA) in combined phacoemulsification with 23-gauge transconjunctival sutureless vitrectomy (TSV) versus combined phacoemulsification with 20-gauge standard vitrectomy. Methods: This is a prospective comparative study comprised of 40 eyes from 37 consecutive patients. Twenty eyes (19 patients) underwent combined phacoemulsification and 23-gauge TSV, and 20 eyes (18 patients) underwent combined phacoemulsification and 20-gauge standard vitrectomy. Corneal topography was obtained preoperatively and postoperatively at weeks 1, 4, 8, and 12. Main outcome measurement was SIA consisting of astigmatic amplitude and axis from cross cylinder form calculated by rectangular coordinate method using the Holladay-Cravy-Koch formula. Results: The mean SIA was 1.07 ± 0.57 diopters (D) in the 23-gauge TSV group and 2.09 ± 0.81 D in the 20-gauge group at postoperative week 1. SIA of both groups at weeks 4, 8, and 12 significantly decreased from the SIA at postoperative week 1 (p < 0.0001 for all 3 weeks). SIA of the 23-gauge TSV group was significantly less than that of the 20-gauge standard vitrectomy group at each postoperative period (p = 0.001). SIA of the gas tamponade group in the 23-gauge TSV was significantly greater than that of the non-gas tamponade group at postoperative week one (p = 0.039). Shifts of axis to other meridians returned to preoperative meridian in 12 eyes (85.7%) for the 23-gauge group and seven eyes (43.8%) for the 20-gauge group. Conclusion: Combined phacoemulsification and pars plana vitrectomy (23-gauge and 20-gauge) could induce significant SIA at postoperative week 1, and decrease over 3 months. However, 23-gauge TSV showed less SIA and early stabilization compared to the 20-gauge standard vitrectomy.