He, M.; (2006) Prevalence and clinical characteristics of primary angle closure in adult Chinese in Liwan District, Guangzhou. Doctoral thesis , University of London.

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Abstract

In 2003, a population survey was carried out in Guangzhou, a large city in southern China, to investigate the prevalence and clinical characteristics of glaucoma in a representative sample of people in one city district. Standard laser iridotomy was performed in one randomly selected eye of the subjects with suspected angle-closure (those with occludable angles but without raised intraocular pressure or peripheral anterior synechiae). Clinical ocular and ultrasound biomicroscopic examination were carried out before and 2 weeks after laser treatment. Among 1,405 people aged 50 years and over examined (at a 75.3% response rate), crude prevalence of all glaucomatous optic neuropathy was 3.8% (95%CI: 2.8-4.8%), increasing from 1.1% in the 50-59 age group to 5.5% in those aged 70 years and older. The ratio of PACG / POAG cases was 21/29. Prevalences of occludable angles and primary angle closure were found to be 10.2% (95%CI: 8.6-11.8%) and 2.4% (95%CI: 1.6-3.1%) respectively. Seventy-four subjects in underwent laser iridotomy on one randomly selected eye. The mean IOP before laser was close to the population mean, and fell by an average of 3 mm Hg after laser. Mean ACD, lens thickness and axial length did not change after treatment. UBM quantitative analysis suggested mean drainage angle width increased by 2.6 times in superior quadrant. The iris curvature radius increased from 5.02 mm to 13.31 mm after treatment suggesting marked flattening of the iris. Distance between ciliary body to trabecular meshwork increased from 0.537mm to 0.561mm (PO.0001) suggesting the backward movement of the ciliary body. Iris thickness at 750 micro m location increased after laser suggesting flattening and a reduction of tension on the iris after pupil block had been eradicated. About one-fifth (14/74) of the treated eyes remained "gonioscopically occludable" even after a patent peripheral iridotomy (PI) had been created. The UBM characteristics of those remaining occludable included: anterior rotation of the ciliary body, angulated or anterior location of the iris insertion and thickening of peripheral iris. This study suggests that the prevalence of primary angle closure was comparable to that found in Singapore and Mongolia. Pupil-block was a significant mechanism in 80% of cases of angle-closure.

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