Predicting the Effect of Laser Peripheral Iridotomy

Overview

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.

Full Title of Study: “Prediction of the Degree of Angle Opening Distance in Patients With Primary Angle Closure Suspect After Laser Peripheral Iridotomy”

Study Type

  • Study Type: Observational [Patient Registry]
  • Study Design
    • Time Perspective: Prospective
  • Study Primary Completion Date: December 31, 2020

Detailed Description

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.

Interventions

  • Other: pupillary block group
    • According to the configurations of angle closure, the pupillary block group is defined as the iris bombe.
  • Other: plateau iris group
    • According to the configurations of angle closure, the plateau iris group is defined as the thickness of the peripheral iris.
  • Other: mixing mechanism group
    • According to the configurations of angle closure, the mixing mechanism group is defined as the iris bombe plus thickening of the peripheral iris.

Arms, Groups and Cohorts

  • Pupillary block group
    • According to the configurations of angle closure, the pupillary block group is defined as the iris bombe.
  • plateau iris group
    • According to the configurations of angle closure, the plateau iris group is defined as the thickness of the peripheral iris.
  • mixed mechanism group
    • According to the configurations of angle closure, the mixing mechanism group is defined as the iris bombe plus thickening of the peripheral iris.

Clinical Trial Outcome Measures

Primary Measures

  • the changes in anterior opening distance before and after LPI
    • Time Frame: between the baseline and 1 hour before discharge
    • 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

Participating in This Clinical Trial

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.

Gender Eligibility: All

Minimum Age: 20 Years

Maximum Age: N/A

Are Healthy Volunteers Accepted: No

Investigator Details

  • Lead Sponsor
    • Zhongshan Ophthalmic Center, Sun Yat-sen University
  • Provider of Information About this Clinical Study
    • Principal Investigator: Mingkai Lin, chief physician – Zhongshan Ophthalmic Center, Sun Yat-sen University
  • Overall Official(s)
    • Mingkai Lin, MD, Study Chair, Zhongshan Ophthalmic Center, Sun Yat-San University
  • Overall Contact(s)
    • Yuying Zhou, Master, 8615270988097, 2053552500@qq.com

References

He M, Jiang Y, Huang S, Chang DS, Munoz B, Aung T, Foster PJ, Friedman DS. Laser peripheral iridotomy for the prevention of angle closure: a single-centre, randomised controlled trial. Lancet. 2019 Apr 20;393(10181):1609-1618. doi: 10.1016/S0140-6736(18)32607-2. Epub 2019 Mar 14.

He M, Friedman DS, Ge J, Huang W, Jin C, Lee PS, Khaw PT, Foster PJ. Laser peripheral iridotomy in primary angle-closure suspects: biometric and gonioscopic outcomes: the Liwan Eye Study. Ophthalmology. 2007 Mar;114(3):494-500. Epub 2006 Nov 21.

He M, Foster PJ, Ge J, Huang W, Zheng Y, Friedman DS, Lee PS, Khaw PT. Prevalence and clinical characteristics of glaucoma in adult Chinese: a population-based study in Liwan District, Guangzhou. Invest Ophthalmol Vis Sci. 2006 Jul;47(7):2782-8.

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