We analyzed 22 eyes with primary angle-closure glaucoma that underwent initial laser iridotomy to determine which factors could lead to subsequent trabeculectomy. Twenty-two eyes were divided into two groups: (1) the eyes in which intraocular pressure (IOP) could be controlled by iridotomy and/or topical medication (iridotomy success group, 15 eyes) and (2) the eyes that underwent trabeculectomy to control IOP in spite of a patent opening (iridotomy failure group, 7 eyes). The clinical variables between the two groups were analyzed. Age, sex, visual field defect, presenting IOP and cup/disk ratio were not significantly different between the iridotomy success and failure groups. However, presence of peripheral anterior synechiae (PAS) greater than 50% was found more frequently in the iridotomy failure group as compared with the iridotomy success group (4/7 vs. 1/15, p = 0.02). Dilated, miotic-resistant pupils were observed only in the iridotomy failure group (4/7 vs. 0/15, p = 0.004). PAS greater than 50% and dilated, fixed pupils were observed in these same cases (4 eyes). Our results suggest that laser iridotomy may not be helpful in cases with dilated and miotic-resistant pupils with formation of extensive PAS.