Background Argon laser peripheral iridoplasty (ALPI) is proved to be effective in lowering intraocular pressure (IOP) of patients with mild acute primary angle closure (APAC).It is unclear whether this laser treatment is equally efficient in managing patients with severe APAC.This study aimed to evaluate the IOP-lowering efficacy of ALPI and laser peripheral iridotomy (LPI) on patients with refractory APAC,who have previously responded poorly to intensive medical therapy.Methods Thirty-six patients (8 men and 28 women) were identified as medically refractory APAC,who still had ocular pain,red eye,hazy cea,closed anterior chamber (AC) angle,and IOP of not less than 21 mmHg after two days or more of anti-glaucoma medication.All enrolled patients underwent ophthalmologic examinations including measurement of visual acuity (VA),best corrected VA (BCVA),IOP,biomicroscopy,and gonioscopy followed by ALPI immediately in the APAC eye and LPI in both eyes.Results All patients were affected unilaterally,with average age of (54.6±11.7) (range,37.0-75.0) years old.The mean IOP value of the affected eyes dropped from (31.6±7.7) (range,21.0-39.0) mmHg at enrollment to (18.4±8.7) (range,10.0-27.0) mmHg 2 hours after ALPI.At follow-up day 7,the mean IOP value maintained at (14.8±4.2) (range,9.0-21.0)mmHg,which was significantly different (P=0.000) compared with baseline.The average decrease of IOP in the APAC eyes was (16.8±7.4) (range,12.0-21.0) mmHg.At follow-up three years later,the mean IOP of the APAC eyes stabilized at (16.3±3.2) (range,9.0-20.0) mmHg with at least 180° of AC angle opened.Conclusion ALPI and LPI lower the IOP of medically refractory cases of APAC though they have responded poorly to anti-glaucoma medication.