mechanisms causing angle closure can be described according to the anatomical location of the obstruction
Last reviewed 01/2018
Mechanisms causing angle closure can be described according to the anatomical location of the obstruction:
- pupillary block mechanism
- seen in around 75%
- aqueous flow from the posterior chamber to the anterior chamber through the pupil is hampered resulting in an increase in posterior chamber pressure and anterior bowing of the iris
- may be physiological (during reading in poor light) or pharmacological
- narrow anterior segment and the age related increase of lens volume may act as predisposing factors
- is associated with hypermetropia
- obstruction at the level of the iris and/or cilliary body
- caused by variation in anatomy of the iris and cilliary body resulting in iridotrabecular contact
- e.g. - thick iris, more anterior iris insertion and more anterior cilliary
body position
- obstruction at the level of the lens
- thicker (in diabetes or post traumatic cataract), more anteriorly positioned
(retinal gas or oil tamponade) or subluxation (Marfan syndrome or trauma)
of the lens may result in secondary angle closure
- thicker (in diabetes or post traumatic cataract), more anteriorly positioned
(retinal gas or oil tamponade) or subluxation (Marfan syndrome or trauma)
of the lens may result in secondary angle closure
- obstruction posterior to the lens (aqueous misdirection syndrome)
- may be seen after trabeculectomy, lens extraction, laser iridotomy
- aqueous is misdirected in to the vitreous causing lens/iris diaphragm to push forward and obstruct the anterior chamber angle (1)
Reference:
- 1. European Glaucoma Society (EGS) 2008. Terminology and guidelines for glaucoma (3rd edition)