The Glaucoma Wiki

This wiki is a top level overview and information resource for Glaucoma. It is not a substitute for medical advice, and you should always consult your doctor or other qualified health professional.

What is Glaucoma?

Glaucoma is a group of eye diseases characterized by damage to the optic nerve and visual field loss. The optic nerve carries images received by the eye to the brain. Untreated, Glaucoma causes damage to the optic nerve and, eventually, vision loss. Vision loss is usually painless, and patients become aware of vision loss gradually.

Glaucoma is a leading cause of blindness worldwide. It occurs when damage is done to the optic nerve, which transmits visual information from the eye to the brain. This damage is caused by elevated pressure in the eye, which is often due to a malfunctioning drainage system. The symptoms include blurred vision, loss of peripheral vision, and eye pain. Most cases of glaucoma are initially asymptomatic, and many people go blind from the disease without even realizing they had it.

The good news is that glaucoma is not the end of the world. The condition is treatable with medications and surgery, and it can often be prevented with early diagnosis and treatment.

Glaucoma Definition

A progressive and devastating blinding disease, which, left untreated, will usually lead to blindness.

Types of Glaucoma

Glaucoma is a broad term which covers several different types of diseases. They differ in cause, presentation, and severity. Glaucoma, also known as ocular hypertension, is a group of diseases that cause damage to the eye's optic nerve. The optic nerve carries vision from the eye to the brain, and damage to the optic nerve leads to loss of peripheral vision and eventually, to blindness.

There are two main types of glaucoma. One, called open-angle glaucoma, is far more common than the other type, called angle-closure glaucoma. An enlarged and distended eye can result from open-angle glaucoma. People who have angle-closure glaucoma have an obstruction to the drainage of fluid out of the eye. This causes an eye that is smaller and more painful.

Two types of glaucoma that are of particular interest are:

Primarily open-angle glaucoma (POAG), also called simple glaucoma or low-tension glaucoma. In this type, there is no noticeable eye enlargement or pain until the final stage of the disease.

Primary angle-closure glaucoma (PACG), also called closed-angle glaucoma, or angle-closure glaucoma. This occurs when the eye's drainage angle is obstructed, preventing the fluid from flowing out of the eye. The blocking may be due to a condition called angle closure, a condition in which the drainage angle collapses, trapping the fluid and preventing the fluid from flowing out. Because this is one of the most common types of glaucoma, it has been the focus of much research. Both the closed angle and open angle types of glaucoma are related to high pressure inside the eye.

Glaucoma is not a single disease. It is rather a family of diseases that share a common symptom: progressive vision loss. Like other chronic diseases, glaucoma is usually slow and painless, which can delay detection.

Signs and Symptoms

Glaucoma is often referred to as “the silent thief of sight.” Vision loss is gradual, but if untreated it may eventually lead to blindness.

The most common symptom of glaucoma is a gradual and painless reduction in vision.

Primary open angle glaucoma (POAG) and primary angle closure glaucoma (PACG) are both common types of glaucoma.

The second most common type of glaucoma is primary congenital glaucoma (PCG) which occurs in young children.

It is estimated that POAG accounts for approximately 75% of cases of glaucoma worldwide and is the most common type in developed countries.

What Causes Glaucoma?

The exact cause of glaucoma is not well known. Primary open-angle glaucoma (POAG) occurs when there is too much fluid inside the eye (increased intraocular pressure or IOP).

Primary angle-closure glaucoma (PACG) is caused by blockage of the drainage angle of the eye.

Primary congenital glaucoma (PCG) is the result of developmental malformations of the eye.

Glaucoma is generally caused by increased pressure in the eye. The two most common types are primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG). POAG is more common than PACG

Glaucoma does not cause eye pressure, it is caused by high eye pressure. Eye pressure is a risk factor (amongst others) for glaucoma. Furthermore, eye pressure refers to intraocular pressure (IOP). That is, it is the pressure between the cornea and the lens. It is different from the general (circadian, daily) blood pressure which measures blood pressure in the arteries. Although it is recognized that IOP is often not high when glaucoma is first diagnosed, we can still say that IOP is a risk factor for glaucoma. That is why an optometrist, an ophthalmologist, or a nurse practitioner would use a device called a tonometer to measure your eye pressure (IOP) when they diagnose glaucoma.

Glaucoma and ocular hypertension (elevated intraocular pressure) are very different terms. They refer to two different conditions: Glaucoma is an optic neuropathy which is defined as a slowly progressing disease while ocular hypertension is defined as an IOP higher than normal in the absence of glaucomatous damage.

Just having high eye pressure is not enough to get glaucoma. You need to have the other factors associated with it. These other factors are not definitive risk factors. It is true that ahigher pressure could be associated with glaucoma, but it is also true that having high eye pressure is just part of the picture and it may not be the most important factor.

Secondary glaucoma

Secondary glaucoma is not as common as primary glaucoma. It occurs when other eye or general health problems are causing the eye to increase intraocular pressure. These problems may include:

  • Antiretroviral therapies such as didanosine, isoniazid, and steroids
  • Coats disease, which causes abnormal growth of new blood vessels in the retina
  • Hemorrhage
  • Inflammatory disease
  • Insulin dependent diabetes mellitus

Large angle neovascular glaucoma

Trigeminal glaucoma, where increased intraocular pressure results from stimulation of intraocular pressure receptor neurons by the trigeminal nerve.

A retinal detachment may develop as a result of ocular hypertension, causing an increased pressure in the vitreous cavity. This is called 'retinal detachment with high intraocular pressure.' It is rare.

Can gluacoma be cured?

Most glaucoma patients see a doctor for years and get more and more prescriptions to slow down the progression of glaucoma. Unfortunately, once damage to the retina has been caused by glaucoma, there are not currently any treatments to restore it. This is an active area of research, though, so new restorative treatments may be just a few years away.

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