eye disorders
Angle Closure Glaucoma
Pathophysiology of Angle Closure Glaucoma
Angle closure may be primary (cause is unknown) or secondary to another condition and can be acute, subacute (intermittent), or chronic. Narrow angles are not present in young people. As people age, the lens of the eye continues to grow. In some but not all people, this growth pushes the iris forward, narrowing the angle. Risk factors for developing narrow angles include family history, advanced age, and race; risk is higher in Asian and Inuit populations and lower in European and African populations. In people with narrow angles, the distance between the iris at the pupil and the lens is also very narrow. When the iris dilates, forces pull the iris centripetally and posteriorly causing increasing iris–lens contact, which prevents aqueous from passing between the lens and iris, through the pupil, and into the anterior chamber (this mechanism is termed pupillary block). Pressure from the continued secretion of aqueous into the posterior chamber by the ciliary body pushes the peripheral iris anteriorly (causing a forward-bowing iris called iris bombe), closing the angle. This closure blocks aqueous outflow, resulting in rapid (within hours) and severe (>40 mm Hg) elevation of intraocular pressure (IOP). Nonpupillary block mechanisms include plateau iris syndrome, in which the central anterior chamber is deep but the peripheral anterior chamber is made shallow by a ciliary body that is displaced forward. Acute angle-closure glaucomarequires immediate recognition and treatment because vision can be lost quickly and permanently. Intermittent angle-closure glaucomaoccurs if the episode of pupillary block resolves spontaneously after several hours, usually after sleeping supine. Chronic angle-closure glaucomaoccurs if the angle narrows slowly, allowing scarring between the peripheral iris and trabecular meshwork; IOP elevation is slow. Pupillary dilation (mydriasis) can push the iris into the angle and precipitate acute angle-closure glaucoma in any person with narrow angles. The mechanical obstruction of the angle is due to a coexisting condition, such as Diabetic Retinopathy (PDR), ischemic 