Dysphotopsia after temporal versus superior laser peripheral iridotomy: a prospective randomized paired eye trial

Purpose To determine if the location of neodymium:yttrium–aluminum–garnet laser peripheral iridotomy (LPI) is related to the occurrence of postoperative visual dysphotopsia. Design Randomized, prospective, single-masked, paired-eye comparative clinical trial. Methods setting: Private subspecialty clinic in Mississauga, Canada. study population: Patients with primary angle closure or primary angle-closure suspects were recruited and randomized to receive LPI temporally in one eye and superiorly in the other. Patients were masked to the location of treatment in each eye. intervention: Temporal or superior LPI. main outcome measures: Occurrence of new-onset linear dysphotopsia. Other visual disturbances also were assessed using a questionnaire before and 1 month after intervention. Secondary outcome measures included eyelid position, laser parameters, and any intraoperative complications. Results A total of 208 patients were recruited to the study, of which 169 (84%) completed it. New-onset linear dysphotopsia was reported in 18 (10.7%) eyes with superior LPI versus 4 (2.4%) eyes with temporal LPI ( P = .002). Eleven eyes (6.5%) with superior LPI reported linear dysphotopsia despite complete eyelid coverage of the iridotomy. No significant differences were found with other visual disturbances between them. There was more pain experienced by the temporal LPI (2.8 ± 2.2 vs 2.1 ± 2.0; P = .001), despite no difference in laser energy or number of shots. Intraoperative rates of hemorrhage were similar (8.9% vs 10.1%; P = .71). Conclusions Temporal placement of LPI is safe and was found to be less likely to result in linear dysphotopsia as compared with superior placement. Temporal iris therefore may be considered a preferred location for LPI.