Glaucoma is the second leading cause of blindness and the most common cause of irreversible blindness worldwide. Primary angle closure glaucoma (PACG) accounts for 25% of glaucoma. Laser peripheral iridotomy(LPI) has become the first line treatment for PACG and primary angle closure (PAC). The mechanism of LPI is to use laser to create a hole in peripheral iris to relieve pupil block, deepen anterior chamber, expand chamber angle,restore pathway of physiological aqueous discharge and reduce intraocular pressure. Studies have shown that LPI can control intraocular pressure well in all stages of PAC, which is safe for PAC.