Glaucoma

]

Types

The most common type, primary open angle glaucoma (POAG), frequently has no symptoms and has been nicknamed "the sneak thief of sight". One factor may be a relative obstruction on the outflow of aqueous humour from the eye.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Aqueous humour is produced by the ciliary body of the eye, and then flows through the pupil and into the anterior chamber.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The trabecular meshwork then drains the humour to Schlemm's canal, and ultimately to the venous system.

Related Topics:
Trabecular meshwork - Schlemm's canal - Venous system

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

All eyes have some intraocular pressure, which is caused by some resistance to the flow of aqueous through the trabeculum and Schlemm's canal.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

If the intraocular pressure (IOP) is too high, (>21.5 mm Hg), the pressure exerted on the walls of the eye result in compression of the ocular structures. However, other factors such as disturbances of blood flow in the optic nerve head may interact with IOP to affect the optic nerve. In one third of cases of POAG there is statistically normal IOP. This is called normal tension glaucoma (NTG). Because optic nerve examination and perimetry testing are not always done in addition to IOP measurement in those at risk, NTG is underdiagnosed and the condition presents late.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Another type, acute angle-closure glaucoma, is characterized by an acute rise in the intraocular pressure. This occurs in susceptible eyes when the pupil dilates and blocks the flow of fluid through it, leading to the peripheral iris blocking the trabecular meshwork. Acute angle-closure glaucoma can cause pain and reduced visual acuity (blurred vision), and may lead to irreversible visual loss within a short time. This is an ocular emergency requiring immediate treatment. Many people with glaucoma experience halos around bright lights as well as the loss of sight characterized by the disease.

Related Topics:
Iris - Trabecular meshwork - Pain - Visual acuity - Visual loss - Halo

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Primary congenital glaucoma or buphthalmos is a rare genetic disease affecting infants. Newborns present with enlarged globes and clouded corneas. It is thought that reduced trabecular permeability is the cause of increased intraocular pressure. Surgery is the treatment.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Secondary glaucoma occurs as a complication of various medical conditions such as eye surgery, advanced cataracts, eye injuries, some eye tumors, uveitis, diabetes or use of corticosteroid drugs.

Related Topics:
Cataracts - Uveitis - Diabetes - Corticosteroid

~ ~ ~ ~ ~ ~ ~ ~ ~ ~