AIM: To investigate the efficacy and safety of krypton laser peripheral iridoplasty (LPIP) for Chinese patients with primary angle closure (PAC) or primary angle-closure glaucoma (PACG) status post laser iridotomy in reversing the positive results of the dark room provocative test (DRPT).METHODS:This study was prospective, noncomparative, interventional case series. Thirty-three patients (thirty-eight eyes) with PAC or PACG status post patent laser iridotomy and maintained normal intraocular pressure (IOP) but with positive DRPT results were enrolled. All the subjects were treated with krypton LPIP. DRPT was repeated after krypton LPIP. Results of DRPT were recorded. The visual acuity, IOP and gonioscopy were analyzed before and after krypton LPIP. A minimum time limit for follow-up was 6mo.RESULTS:Thirty-three patients (thirty-eight eyes) were followed for 17.7±8.37mo (range 7-41mo) after LPIP. Positive results of DRPT decreased from 38 eyes to 9 eyes (23.7%) after LPIP. Peripheral anterior synechiae of angle in 34 of 38 eyes (89.5%) remained unchanged at dynamic gonioscopy throughout the follow-up period after LPIP.CONCLUSION:LPIP decreased positive rates of the DRPT significantly. The mechanism may be that LPIP minimized contact between the peripheral iris and trabecular meshwork, which is a key factor for developing peripheral anterior synechiae.