Understanding Glaucoma

Types of Glaucoma?

There are many different types of glaucoma. The two major types are primary open-angle and angle-closure.

Open-angle glaucoma
Open-angle glaucoma (also called chronic open angle or primary open angle) accounts for 60-70% of glaucoma cases in the United States. In open-angle glaucoma, the aqueous humor is unable to drain out of the eye. For unknown reasons, the trabecular meshwork (the eye's filtration area) does not function normally, the pressure in the eye increases, and the optic nerve is damaged. Most people do not experience symptoms and no early warning signs until their vision is compromised and extensive damage to the optic nerve has been done. This type of glaucoma develops slowly and sometimes without noticeable sight loss for many years. Eye drops are generally prescribed to lower the eye pressure. In some cases, surgery is performed if the lOP cannot be adequately controlled with medical therapy.

Pigmentary glaucoma
This is an inherited type of open angle glaucoma that most commonly affects myopic men in their 20s or 30s. Myopia (nearsightedness) causes the eyes to have a concave iris, creating a wide angle. This causes the color (pigment) layer of the eye, the iris, to rub off onto the lens, where it can shed into the aqueous humor and the trabecular meshwork. The pigment can clog the pores of the trabecular meshwork, which prevents adequate aqueous humor drainage and increases lOP.

Angle-closure glaucoma
Angle-closure glaucoma, also known as acute glaucoma or narrow-angle glaucoma accounts for fewer than 10% of cases. This type of glaucoma is much more rare and is very different from open angle glaucoma in that the eye pressure usually rises very quickly. This type results from an abnormality in eye structure usually in the front of the eye. In most casas, the iris occludes (blocks) the trabecular meshwork, preventing drainage of aqueous humor and raising intraocular pressure.

If the drainage channel is completely blocked, lOP rises suddenly, causing acute angle-closure glaucoma. Symptoms may be severe and include extreme eye pain, nausea, blurred vision, and halos around lights. Acute angle-closure glaucoma is a medical emergency that must be treated by an ophthalmologist immediately. Permanent vision loss can occur within days. Treatment of angle glaucoma usually involves surgery to remove a small portion of the outer edge of the iris. This helps unblock the drainage canals so that the extra fluid can drain. Usually surgery is successful and long lasting. However, you should still receive regular glaucoma check-ups.

Symptoms of angle closure glaucoma may include headaches, eye pain, nausea, rainbows around lights at night, and very blurred vision.

Pediatric/Congenital glaucoma
The Pediatric glaucoma's consist of congenital glaucoma (present at birth), infantile glaucoma (appears during the first three years), juvenile glaucoma (Age three through the teenage or young adult years), and all the secondary glaucomas occurring in the pediatric age group.

Congenital glaucoma is present at birth and most cases are diagnosed during the first year of life. Sometimes symptoms are not recognized until later in infancy or early childhood.

When glaucoma is diagnosed before a child's third birthday, it is considered congenital (present since birth). In approximately one-third of children, it is inherited through an autosomal recessive gene. Autosomal means that boys and girls are affected equally, and recessively indicates that both parents have the gene. The risk is 25% with each pregnancy that the infant will have congenital glaucoma when both parents are carriers (i.e., they do not have the condition but they can pass it on to their child).

Normal tension glaucoma
Normal tension glaucoma is also known as low-tension glaucoma or normal pressure glaucoma. In this type of glaucoma the optic nerve is damaged even though intraocular pressure (lOP) is not very high. Doctors do not know why some people's optic nerves suffer damage even though pressure levels are in the "normal" range.

Those at higher risk for this form of glaucoma are people with a family history of normal tension glaucoma, people of Japanese ancestry, and people with a history of systemic heart disease, such as irregular heart rhythm. Normal tension glaucoma is usually detected after an examination of the optic nerve.

Secondary glaucoma
Glaucoma can occur as the result of an eye injury, inflammation, tumor or advanced cases of cataract or diabetes. Certain drugs such as steroids can also cause secondary glaucoma. This form of glaucoma may be mild or severe. The type of treatment will depend on whether it is open-angle or angle-closure glaucoma.

  • Pseudoexfoliative Glaucoma
    This form of secondary open angle glaucoma occurs when a flaky, dandruff-like material peels off the outer layer of the lens within the eye. The material collects in the angle between the cornea and iris and can clog the drainage system of the eye, causing eye pressure to rise.

Pseudoexfoliative Glaucoma is common in those of Scandinavian descent. Treatment usually includes medications or surgery.

  • Pigmentary Glaucoma
    A form of secondary open angle glaucoma, this occurs when the pigment granules in the back of the iris (the colored part of the eye) break into the clear fluid produced inside the eye. These tiny pigment granules flow toward the drainage canals in the eye and slowly clog them, causing eye pressure to rise. Treatment usually includes medications or surgery.
  • Traumatic Glaucoma
    Injury to the eye may cause secondary open angle glaucoma. This type of glaucoma can occur immediately after the injury or years later.

It can be caused by blunt injuries that "bruise" the eye (called blunt trauma) or by injuries that penetrate the eye.

In addition, conditions such as severe nearsightedness, previous injury, infection, or prior surgery may make the eye more vulnerable to a serious eye injury.

  • Neovascular Glaucoma
    The abnormal formation of new blood vessels on the iris and over the eye's drainage channels can cause a form of secondary open angle glaucoma.

Neovascular glaucoma is always associated with other abnormalities, most often diabetes. It never occurs on its own. The new blood vessels block the eye's fluid from exiting through the trabecular meshwork (the eye's drainage canals), causing an increase in eye pressure. This type of glaucoma is very difficult to treat.

  • lrido Corneal Endothelial Syndrome (ICE)
    This rare form of glaucoma usually appears in only one eye, rather than both. Cells on the back surface of the cornea spread over the eye's drainage tissue and across the surface of the iris, increasing eye pressure and damaging the optic nerve. These corneal cells also form adhesions that bind the iris to the cornea, further blocking the drainage channels.

This syndrome occurs more frequently in light-skinned females. Symptoms can include hazy vision upon wakening and the appearance of halos around lights. Treatment can include medications and filtering surgery. Laser therapy is not effective in these cases.

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