Visual field protocol
Central VFs (Humphrey Field Analyzer Central 10–2 Swedish Interactive Threshold Algorithm-Standard test, Carl Zeiss Meditec, San Leandro, CA) were performed preoperatively and 6 months postoperatively. The test was performed in both eyes with the fellow eye first and repeated if they failed to achieve a pre-defined reliability criterion of < 15% false positives. Only VFs meeting these criteria were analysed. Technicians and assessors were masked to the forceps used.