Predicting the Effect of Laser Peripheral Iridotomy

Study Overview
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Brief Summary
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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.

Detailed Description
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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.

Official Title
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Prediction of the Degree of Angle Opening Distance in Patients With Primary Angle Closure Suspect After Laser Peripheral Iridotomy

Conditions
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Glaucoma

Intervention / Treatment
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* Other: pupillary block group
* Other: plateau iris group
* Other: mixing mechanism group


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Patient was diagnosed of primary angle closure angle suspect; received ultrasound Biomicroscopy before and after laser peripheral iridotomy; Voluntary participation in this study; Have enough language comprehension ability; Patient or his legal representative has sign the informed consent. Exclusion Criteria: severe health problems resulting in a life expectancy of less than 1 year; previous intraocular surgery or penetrating eye injury; media opacity preventing laser peripheral iridotomy; Researchers think not suitable to participate in this clinical trial subjects; Refused to sign the informed consent.; 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.

Ages Eligible for Study
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Minimum Age: 20 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Pupillary block group<br>According to the configurations of angle closure, the pupillary block group is defined as the iris bombe. | Other: pupillary block group<br>* According to the configurations of angle closure, the pupillary block group is defined as the iris bombe.<br>|
| plateau iris group<br>According to the configurations of angle closure, the plateau iris group is defined as the thickness of the peripheral iris. | Other: plateau iris group<br>* According to the configurations of angle closure, the plateau iris group is defined as the thickness of the peripheral iris.<br>|
| mixed mechanism group<br>According to the configurations of angle closure, the mixing mechanism group is defined as the iris bombe plus thickening of the peripheral iris. | Other: mixing mechanism group<br>* According to the configurations of angle closure, the mixing mechanism group is defined as the iris bombe plus thickening of the peripheral iris.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| the changes in anterior opening distance before and after LPI | To compare the difference of anterior opening distance after LPI and baseline parameters before LPI. Anterior opening distance, measured on a line perpendicular to the plane of the trabecular surface 500 μm anterior to the scleral spur and extended to meet the surface of the iris | between the baseline and 1 hour before discharge | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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laser peripheral iridotomy, primary angle closure suspect, angle closure mechanism