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M. He, P.J. Foster, J. Ge, D.S. Friedman, P.T. Khaw; Laser Peripheral Iridotomy in Population–Based Primary Angle–Closure Suspects: The Liwan Eye Study . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3427.
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© ARVO (1962-2015); The Authors (2016-present)
To assess the immediate effect of laser PI and mechanism of angle–closure in Chinese adults with narrow drainage angles
Angle–closure suspects were identified using gonioscopy during a population–based survey in Liwan District, Guangzhou, China. Laser iridotomy was performed in one randomly–selected eye. People with established angle–closure and angle–closure glaucoma were excluded. Gonioscopy, ultrasound biomicroscopy (UBM), intraocular pressure (IOP), ultrasound biometry, optical pachymetry were performed before and two weeks after laser treatment.
A total of 74 people with bilateral narrow angles participated in the study. Iridotomy was patent in all subjects .Mean IOP decreased by 3 mmHg (P<0.001), but axial anterior chamber did not change significantly (P=0.806) after laser. Median Shaffer angle width grade increased significantly from 0.6 units to 2.4 units after the treatment. However, fourteen eyes (19%) had three or more quadrants in which the posterior (usually pigmented) trabecular meshwork could not be seen. These people tended to be younger and male, although the trends toward these characteristics were not statistically significant. Mean angle opening distance (AOD 500) was smaller at baseline in those with residual closure versus those in whom iridotomy successfully opened the angle (0.052 vs 0.108mm, P<0.001). The iris was also thicker (IT500: 0.399mm vs 0.376mm, P=0.043) and the ciliary body more anteriorly rotated (distance between scleral spur and ciliary body: 0.514 vs 0.562mm, P=0.033) in those with residual angle–closure.
The study confirms that laser PI results in a significant increase in angle width in Chinese people with narrow angles. However, one–fifth of eyes treated had clinically significant residual angle–closure following laser iridotomy. Long term, perspective studies with greater sample size are required to confirm that the risk of angle closure and associated glaucoma is reduced after prophylactic laser PI, and to investigate the risk–benefit ratio, prior to recommending wide–spread use of prophylactic laser in this high–risk population.
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