Sample size
glaucoma-related AEs
According to the Zhongshan Ophthalmic Center’s outpatient record system, (1) the one-year incidence of glaucoma-related AEs in sulcus implantation is 12%. Assuming the in-the-bag implantation would reduce the absolute incidence to 0.7%, to achieve 90% power with a two-sided alpha of 0.0492 (the interim analysis at 6 months postoperatively spending alpha of 0.0054 by O’Brien-Fleming approach), 114 eyes are needed for each group (total of 228 eyes) using Fisher’s exact test with pooled variance. Allowing for a 20% loss to follow-up, 143 eyes should be needed in each group. Assumptions: % of bilateral = 75%, inter-eye correlation among bilateral patients = 0.5. For bilateral patients, two eyes have the same type of surgery. The number of patients (Considering the sample size calculated by the two primary outcomes, the largest one is selected: 114 patients per group, a total of 228 patients.