Primary studies of any design of patients who underwent cataract extraction and who took the anticoagulant warfarin during the perioperative period were eligible for inclusion. Studies had to report the number of bleeding events. Outcomes of interest were bleeding and thromboembolism events. Studies that used other forms of anticoagulation or where warfarin was stopped prior to surgery in all patients were excluded. Surveys were excluded.
The included studies differed in design and included one randomised controlled trial (RCT), one retrospective cohort study, prospective cohort studies and case series. Patient populations had a variety of indications for warfarin including atrial fibrillation, mechanical heart valves or venous thromboembolism. Reported ages (mean or actual) ranged from 66 to 83 years. Length of follow-up ranged from eight minutes to one year. Day of surgery INR (International Normalized Ratio) was between 1.1 and 4.5. Intensity of anticoagulation was between 2.0mg and 3.0mg. The surgical technique for cataract extraction varied with two studies using a clear corneal incision (thought to reduce bleeding risk).
Studies were selected by two reviewers independently. Disagreements were resolved by consensus.