What are the Causes of Glaucoma?

The cause(s) of glaucoma is not understood in most of the cases. How intra-ocular pressure rises in closed angle glaucoma is understood (due to narrowing of irido-corneal angle or the angle where iris and cornea meet, as a result outflow of fluid from eye is blocked, which lead to build up of pressure inside the eye or rise in intra-ocular pressure), but not in case of open angle glaucoma. In open angle glaucoma, the irido-corneal angle is normal and outflow is also normal, but why there is rise in intra-ocular pressure is not well understood.

Closed angle glaucoma:

Because of forward bulging of iris (which leads to narrowing or blockade of irido-corneal angle) fluid (aqueous humor) can not exit properly, leading to accumulation of aqueous humor and build up of intra-ocular pressure. Hence, there is abrupt/sudden and tremendous rise in intra-ocular pressure, causing a medical emergency in many cases of closed angle glaucoma. The cause of bulging of iris forward is not understood in most of the cases.

Open angle glaucoma:

In open angle glaucoma, the irido-corneal angle remains open and patent. However, there may be disturbance (blockade) in trabecular meshwork, which leads to slow drainage of aqueous humor leading to rise in tension inside the eye (intra-ocular pressure). The cause of disturbance (blockade) in trabecular meshwork is not known. Open angle glaucoma may remain asymptomatic for long time and lead to gradual and definite loss of a significant amount of vision, before it becomes symptomatic. Hence, regular eye examination as recommended by American Academy of Ophthalmology should be done.

Pigmentary glaucoma:

In pigmentary glaucoma there is deposition of pigments from iris (contain large amount of pigment which give color to iris) to the outflow channel of aqueous humor (trabecular meshwork) and gradual narrowing and blockade of the channel, leading to gradual rise in intra-ocular pressure.

Normal tension glaucoma:

In normal-tension glaucoma there is no rise in intra-ocular pressure, but there is gradual damage of optic nerve, which influence vision. The cause visual optic nerve damage in absence of raised intra-ocular pressure is not known. It may be due to sensitivity of optic nerve, reduced blood supply due to atherosclerosis of supplying blood vessels etc.

Developmental glaucoma:

Sometimes infants may be born with glaucoma (congenital glaucoma) or infants (infantile glaucoma) and children (juvenile glaucoma) at early age may be diagnosed with glaucoma. The cause is not known.

  • Ethnic, genetic and gender causes of glaucoma: people from East Asia, Africa, Inuits (20-40 time higher risk) have higher risk of developing glaucoma. There is also genetic risk factor, e.g. individuals with a sibling with glaucoma have 2-4 times higher risk of developing glaucoma.
  • Other causes: Certain drugs such as steroids (if used for long term therapy) may cause glaucoma. Trauma is also a cause of glaucoma.

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