The epidemiology of primary angle closure and associated glaucomatous optic neuropathy.

Angle closure glaucoma is emerging as a leading cause of blindness in the densely populated countries of Asia. It has a greater propensity to cause bilateral blindness than either primary open-angle glaucoma or secondary glaucoma. An estimated 9.4 million people in China aged 40 years and older have glaucomatous optic neuropathy. Approximately 5.2 million people (55%) would be blind in at least one eye. Around 1.7 million (18.1%) would be blind in both eyes. it is likely that PACG is responsible for the vast majority (91%) of bilateral glaucoma blindness in China. The number of Chinese people with an "occludable" drainage angle is in the region of 28.2 million, and of these 9.1 million have significant angle closure. There is a growing emphasis on a revised method of classifying the disease, which reserves the term "glaucoma" for cases with glaucomatous optic neuropathy. The term primary angle closure (PAC) is used in cases with a closed angle and peripheral anterior synechiae or raised intraocular pressure. Risk factors for PAC include older age, female gender, Chinese ethnicity, all of which are associated with anatomical risk factors of central and/or peripherally shallow anterior chambers (usually associated with a thicker, anteriorly-positioned lens), and a shorter axial length of the globe.