@article {Foster486, author = {P J Foster and T Aung and W P Nolan and D Machin and J Baasanhu and P T Khaw and P-H Alsbirk and P S Lee and S K L Seah and G J Johnson}, title = {Defining {\textquotedblleft}occludable{\textquotedblright} angles in population surveys: drainage angle width, peripheral anterior synechiae, and glaucomatous optic neuropathy in east Asian people}, volume = {88}, number = {4}, pages = {486--490}, year = {2004}, doi = {10.1136/bjo.2003.020016}, publisher = {BMJ Publishing Group Ltd}, abstract = {Background/aim: A current consensus in epidemiological studies of primary angle closure (PAC) is to diagnose the condition only if the posterior (usually pigmented) trabecular meshwork is seen for less than 90{\textdegree} of the angle circumference, termed an {\textquotedblleft}occludable angle.{\textquotedblright} The authors sought to assess the validity of this epidemiological classification by exploring the relation between drainage angle width, peripheral anterior synechiae (PAS) and glaucomatous optic neuropathy (GON). Methods: 918 Mongolians and 995 Chinese Singaporeans, both groups aged 40 years and older were examined in two population based surveys. Gonioscopic angle width was graded in five categories (0 = closed to 4 = wide open) according the scheme described by Shaffer. Cases with secondary PAS were excluded. Results: The rate of PAS was between 0.3\% and 1.7\% in people with wide angles (grades 3 and 4). In those with grade 2 angles, PAS were seen in between 8\% of eyes. In eyes with grade 1 angles, the rate rose to 17\% in Chinese Singaporeans, and 31\% in Mongolians. The odds of PAS were higher in people with narrower angles. However, there was a greater absolute number of people with PAS whose drainage angles were classified as {\textquotedblleft}not occludable{\textquotedblright} than those classified {\textquotedblleft}occludable.{\textquotedblright} Conclusions: The traditional view that primary angle closure becomes a significant possibility in drainage angles of ⩽ grade 2 (approximately 20{\textdegree}) is valid in east Asians. The definition of an {\textquotedblleft}occludable{\textquotedblright} angle examined here excludes many people with PAS. This probably serves to underemphasise the role of PAC in population surveys of glaucoma prevalence in Asian people.}, issn = {0007-1161}, URL = {https://bjo.bmj.com/content/88/4/486}, eprint = {https://bjo.bmj.com/content/88/4/486.full.pdf}, journal = {British Journal of Ophthalmology} }