Anterior chamber of eyeball
|Anterior chamber of eyeball|
Anterior part of human eye, with anterior chamber at right.
Schematic diagram of the human eye.
|Latin||camera anterior bulbi oculi|
The anterior chamber (AC) is the fluid-filled space inside the eye between the iris and the cornea's innermost surface, the endothelium. Aqueous humor is the clear fluid that fills the anterior chamber. Hyphema, anterior uveitis and glaucoma are three main pathologies in this area. In hyphema, blood fills the anterior chamber as a result of a hemorrhage, most commonly after a blunt eye injury. Anterior uveitis is an inflammatory process affecting the iris and ciliary body, with resulting inflammatory signs in the anterior chamber. In glaucoma, blockage of the trabecular meshwork prevents the normal outflow of aqueous humour, resulting in increased intraocular pressure, progressive damage to the optic nerve head, and eventually blindness.
The depth of the anterior chamber of the eye varies between 1.5 and 4.0 mm, averaging 3.0 mm. The anterior chamber tends to become shallower at older age, and in eyes with hypermetropia (far sightedness). As the anterior chamber depth decreases below 2.5 mm, the risk for angle closure glaucoma increases. Shallow anterior chambers are endemic in certain areas in India and South East Asia, where angle closure glaucoma is a common eye problem and a leading cause of blindness.
Determining the anterior chamber depth (ACD) is important in estimating the risk of angle closure glaucoma. There are various method of measuring ACD, including examination through a slit lamp, ultrasound and Scheimpflug photography. These methods require sophisticated examination equipment and expertise.
A simpler clinical method of quantitatively estimating ACD using smartphone photography (EZ ratio) was developed by Dr Ehud Zamir from the Centre for Eye Research Australia, the University of Melbourne, and published in 2016.
To calculate the estimated anterior chamber depth, the patient looks at a target in the distance with one eye covered. The examiner takes a digital photograph of the open, examined eye, from the side, perpendicular to the visual axis (a profile photograph).
E:Z ratio is the arithmetic ratio between E and Z.
Anterior chamber depth (expressed in millimetres) = -3.3 x EZ ratio + 4.2
Associated immune deviation
One peculiar feature of the anterior chamber is dampened immune response to allogenic grafts. This is called anterior chamber associated immune deviation (ACAID), a term introduced in 1981 by Streilein et al. This phenomenon is relevant to the fact that the eye is considered an "immune privileged site", like the brain and the testis.
- Cassin, B.; Solomon, S. (1990). Dictionary of eye terminology. Gainesville, Fla: Triad Pub. Co. ISBN 0-937404-33-0.
- Zamir, Ehud (2016). "A novel method of quantitative anterior chamber depth estimation using temporal perpendicular digital photography". Translation Vision Science and Technology. 5: 10.
- Streilein JW, Niederkorn JY (May 1981). "Induction of anterior chamber-associated immune deviation requires an intact, functional spleen". J. Exp. Med. 153 (5): 1058–67. PMC . PMID 6788883. doi:10.1084/jem.153.5.1058.
- "Archived copy". Archived from the original on 2015-02-11. Retrieved 2012-07-16.
- Atlas image: eye_2 at the University of Michigan Health System - "Sagittal Section Through the Eyeball"