Elsevier

Ophthalmology

Volume 114, Issue 3, March 2007, Pages 494-500
Ophthalmology

Original Article
Laser Peripheral Iridotomy in Primary Angle-Closure Suspects: Biometric and Gonioscopic Outcomes: The Liwan Eye Study

Presented in part at: Association for Research in Vision and Ophthalmology Annual Meeting, May 2005, Fort Lauderdale, Florida, and World Glaucoma Congress of the Association of International Glaucoma Societies, July 2005, Vienna, Austria.
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Purpose

To assess the immediate effect of laser peripheral iridotomy (LPI) and mechanisms of angle closure in a population-based study of primary angle closure (PAC) suspects.

Design

Prospective interventional study.

Participants

People identified as PAC suspects aged 50 to 79 years from a population-based survey in Guangzhou, China.

Intervention

Laser peripheral iridotomy was performed in 1 randomly selected eye. Examinations were carried out before and 2 weeks after the intervention.

Main Outcome Measures

Intraocular pressure (IOP), ultrasound biometry, optical pachymetry, and gonioscopy.

Results

A total of 72 people with bilateral suspected PAC participated in the study. Mean IOP decreased by 3 mmHg (P<0.001), but axial anterior chamber depth did not change significantly (P = 0.784) after LPI. Median limbal anterior chamber depth increased from 15% to 25% of peripheral corneal thickness (P<0.001, Wilcoxon signed-rank test). Median iridotrabecular angle width increased from 0° to 10° in the superior quadrant and from 10° to 30° in the inferior quadrant (P<0.001). Nevertheless, 14 eyes (19.4%) still had 3 or more quadrants in which the posterior (usually pigmented) trabecular meshwork could not be seen after laser iridotomy.

Conclusions

This study confirms that LPI results in a significant increase in the angle width in Chinese people with narrow angles. However, one fifth of eyes had residual angle closure after LPI. Although this report confirms that iridotomy widens the anterior chamber angle in most PAC suspects, long-term prospective studies with a larger sample size are required to determine if the risks of PAC glaucoma and other related pathologic sequelae are reduced after prophylactic LPI and to investigate the risk-to-benefit ratio before recommending widespread use of prophylactic LPI in this population.

Section snippets

Patients

Detailed study procedures have been reported previously.7 In brief, 1405 persons aged 50 years and older were enrolled from Liwan District, Guangzhou, using cluster random sampling. Ethical approval was obtained from the Zhongshan University Ethical Review Board and the Ethical Committee of Zhongshan Ophthalmic Center. The study was conducted in accordance with the tenets of the World Medical Association’s Declaration of Helsinki, and all participants signed informed consent for participation.

Results

A total of 101 persons with occludable angles in both eyes were considered to be eligible for the study and were offered laser iridotomy, 72 of whom (71.3%) participated (38 right and 34 left eyes). The major reason for nonparticipation among otherwise eligible participants was the decline of consent. There was no difference between participants and nonparticipants in terms of age, gender, baseline IOP, ACD, and angle width (Table 1).

The iridotomy was patent in all but 1 eye after a single

Discussion

Laser peripheral iridotomy is the standard first-line intervention for acute and chronic angle closure.3 It prevents recurrence of acute episodes and eliminates the risk of acute attacks in fellow eyes.4, 12, 13, 14, 15 By allowing aqueous to flow directly through the iridotomy site, LPI equilibrates the pressure between the anterior and posterior chambers. Eliminating this pressure gradient flattens the iris, allowing the peripheral iris to fall backward, resulting in a wider angle

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    Manuscript no. 2006-338.

    The authors have no financial or other conflicts of interest concerning the article.

    Dr He is supported by a University College London Graduate School Research Scholarship, a University College London Overseas Research Scholarship (no. 2001061054), and the Scientific and Technology Foundation of Guangdong Province, Guangzhou, China (grant no.: 2005B30901008). Dr Foster is supported by the Medical Research Council, London, United Kingdom (grant no.: G0401527); Wellcome Trust, London, United Kingdom (grant no.: 075110); and Richard Desmond Charitable Foundation (via Fight for Sight), London, United Kingdom. Prof Khaw is supported by the Medical Research Council (grant no.: G9330070); Moorfields Special Trustees, London, United Kingdom; and Michael and Isle Katz Foundation, London, United Kingdom.

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