Primary angle closure glaucoma

Primary angle closure glaucoma medical terminology is a type of primary glaucoma (wherein there is no obvious systemic or ocular cause) in which rise in intraocular pressure occurs due to blockage of the aqueous humour outflow by closure of a narrower angle of the anterior chamber.
ETIOLOGY
(A) Predisposing risk factors. These can be divided into anatomical and general factors:
I. Anatomical factors. Eyes anatomically predisposed to develop primary angle-closure glaucoma (PACG) include:
Hypermetropic eyes with shallow anterior chamber.
Eyes in which iris-lens diaphragm is placed anteriorly.
Eyes with narrow angle of anterior chamber, which may be due to: small eyeball, relatively large size of the lens and smaller diameter of the cornea or bigger size of the ciliary body.
Plateau iris configuration.
II. General factors include:
Age. PACG is comparatively more common in 5th decade of life.
Sex. Females are more prone to get PACG than males (male to female ratio is 1:4)
Type of personality. It is more common in nervous individuals with unstable vasomotor system.
Season. Peak incidence is reported in rainy season.
Family history. The potential for PACG is generally believed to be inherited.
Race. In caucasians, PACG accounts for about 6% of all glaucomas and presents in sixth to seventh decade. It is more common in South-East Asians, Chinese and Eskimos but uncommon in Blacks. In Asians it presents in the 5th to 6th decade and accounts for 50% of primary adult glaucomas in this ethnic group.

(B) Precipitating factors. In an eye that is predisposed to develop angle closure glaucoma, any of the following factors may precipitate an attack:
Dim illumination, Emotional stress, Use of mydriatic drugs like atropine, cyclopentolate, tropicamide and phenylephrine.
(C) Mechanism of rise in IOP. The probable sequence of events resulting in rise of IOP in an anatomically predisposed eye is as follows:
First of all due to the effect of precipitating factors there occurs mid dilatation of the pupil which increases the amount of apposition between iris and anteriorly placed lens with a considerable pressure resulting in relative pupil block. Consequently the aqueous collects in the posterior chamber and pushes the peripheral flaccid iris anteriorly (Iris bombe), resulting in appositional angle closure due to iridocorneal contact.
Eventually there occurs rise in IOP which is transient to begin with. But slowly the appositional angle closure is converted into synechial angle closure (due to formation of peripheral anterior synechiae) and an attack of rise in IOP may last long.
In some cases a mechanical occlusion of the angle by the iris is sufficient to block the drainage of aqueous. For this reason the instillation of atropine in an eye with a narrow angle is dangerous, since it may precipitate an attack of raised IOP.