This study will compare the angle parameters of patients with PACS before and after LPI. The investigators will analyze the results of patients with different angle closure mechanisms before and after LPI, and participants hope to find the structural parameters for predicting the effect of LPI.

Primary angle-closure glaucoma is the leading cause of blindness worldwide. It is associated with increased intraocular pressure, which causes optic nerve damage and field defects if untreated. The aqueous humor leaves the anterior chamber through the trabecular meshwork and flows into the aqueous vein and the superior scleral vein through the collector channels and Schlemm's canal. If the trabecular meshwork is not blocked, a wide angle allows enough aqueous humor to drain out. The iris corneal translocation may lead to angle-closure glaucoma.

Laser peripheral iridectomy is recognized as the best surgical method to relieve pupil block. Previous studies have shown increased anterior chamber depth (ACD), area (ACA), and volume (ACV), and increased Angle open distance (AOD) after LPI surgery.

However, postoperative outcomes of LPI were not the same for patients with different angle closure mechanisms.

Postoperative outcomes for LPI were best for patients with pupillary block type, but were moderate for patients with plateau iris group and mixed group.

The purpose of this study, conducted in Chinese subjects, aims to use UBM to evaluate changes in the anterior segment parameters of LPI, and to propose methods to predict postoperative outcomes of LPI.

Inclusion Criteria:

1. Patient was diagnosed of primary angle closure angle suspect;
2. received ultrasound Biomicroscopy before and after laser peripheral iridotomy;
3. Voluntary participation in this study;
4. Have enough language comprehension ability;
5. Patient or his legal representative has sign the informed consent.

Exclusion Criteria:

1. severe health problems resulting in a life expectancy of less than 1 year;
2. previous intraocular surgery or penetrating eye injury;
3. media opacity preventing laser peripheral iridotomy;
4. Researchers think not suitable to participate in this clinical trial subjects;
5. Refused to sign the informed consent.;
6. There are important viscera function failure or other serious disease, including clinical related coronary artery disease, cardiovascular disease or myocardial infarction into the group of the first six months; serious neurological or psychiatric illness; serious infections; coagulant function abnormality; general active infectious diseases; malignant tumor; serious immune diseases.

Chinese Patient was diagnosed of primary angle closure angle suspect