Types of Glaucoma
There are several types of glaucoma. Treatment depends on properly identifying precisely which kind is present and determining how the glaucoma may affect the person’s quality of life. The goal of treatment is preservation of health.
The factor common to all types of glaucoma is damage to the optic nerve of the eye. This damage is related to the pressure inside the eye. No matter whether the pressure is high, normal or below normal, it can still cause damage. Most types of glaucoma are chronic, and are present for the person’s lifetime. Some types of glaucoma occur suddenly, but most develop slowly, over months or years.
Most types of glaucoma need some form of treatment. Some people need surgery. Others may need medicine to treat the eye directly, or to treat some other health problem that is affecting the eye. Still others may need to have certain medicines stopped.
Photo by Robert Kump
Primary Open-angle Glaucoma
The most common form of glaucoma is called primary open angle glaucoma. Primary open-angle glaucoma is the garden-variety open-angle glaucoma. “Primary” means there is no known cause. This is typically a disease that has little or no symptoms.
This type of glaucoma, which accounts for 5 to 10% of all glaucomas in the U.S., occurs when the angle between the cornea (the clear window into the eye) and the iris (the colored portion of the eye) is narrow. In all eyes, ocular fluid meets resistance passing from the posterior chamber behind the iris to the anterior chamber in front of the iris. This resistance to the forward flow of fluid causes a slightly increased fluid pressure behind the iris that pushes the iris forward. In eyes with narrow angles, there is not enough room between the iris and the drain of the eye. The forward bowing of the iris from the pressure behind it blocks the drain and thus raises the intraocular pressure.
Iridocorneal Endothelial syndrome or ICE syndrome is a grouping of three closely linked conditions: iris nevus (or Cogan-Reese) syndrome; Chandler’s syndrome; and essential (progressive) iris atrophy, which together also spell the acronym ICE. ICE syndrome is caused by the diseased lining of the cornea, which grows over the drain in the eye, blocking it, and over the iris, causing stretching and a lack of blood supply.
With inflammatory glaucoma the inflammation can either raise or lower the IOP (intraocular pressure). Inflammation causes white cells to form in the liquid in the front of the eye. The cells get trapped in the trabecular meshwork (the “drain”), blocking it. The fluid also becomes thicker and less likely to pass through the drain, and the trabecular beams that make up the drain swell, making the pores between them smaller. Inflammation can also release prostaglandins that increase the flow of fluid out of the eye between the muscle bundles of the eye.
Traumatic glaucoma can occur when trauma injures the trabecular meshwork, the “drain” in the eye. Scarring ensues, and the drain works less well. Early on, blood and inflammatory material can also block the trabecular meshwork. Often there are signs of injury to the drain in the eye. One sign is called an angle recession. With this sign, the iris root is pulled posteriorly away from the trabecular meshwork. That is easily seen during gonioscopy. There is at least a 5% chance that someone with serious eye trauma and an angle recession will develop glaucoma later in life, even if the glaucoma is not present for several years after the trauma.
Glaucoma Suspect (Ocular hypertension, suspicious nerves or fields)
Glaucoma suspect is a term used to describe a person with one or more potential risk factors that may or may not lead to glaucoma, however this person does not show definite signs of glaucomatous damage to the optic nerve or any visual field defects.
Pigmentary glaucoma is a secondary glaucoma caused by an accumulation of pigment in the trabecular meshwork of the eye, blocking the outflow of fluid. Pigmentary glaucoma is usually found in near-sighted individuals in their late 20’s to early 40’s and is more common in males than in females.