Glaucoma is a group of diseases usually characterized by increased intraocular pressure that results in damage to the optic nerve and retinal nerve fibers. However, there are cases of glaucoma where the intraocular pressure is not elevated (normal tension glaucoma), so the term glaucoma is now defined as a collection of disease that causes optic nerve damage. As a result, the diagnosis is no longer determined by an increase in ocular pressure.
Glaucoma is the leading cause of blindness in North America, affecting more than 2.4 million people. Furthermore, it is estimated that another 1 million people are unaware that they have this potentially blinding disease, as this condition progresses slowly and painlessly with no symptoms until significant nerve damage has been done.
- Types of Glaucoma
- Who is at risk?
- Angle-closure Glaucoma
Can be chronic or acute, and occurs when the fluid behind the iris cannont pass through the pupil and pushes the iris forward, preventing fluid drainage. This fluid, called aqueous, builds up, resulting in high intraocular pressure. This usually occurs in patients who have anatomically narrow anterior chamber angles.
- Open-angle Glaucoma
Most common type. Caused by a gradual increase in resistance to normal outflow of aqueous from the eye despite an apparently open anterior chamber angle.
- Congenital Glaucoma
Occuring in newborns or within the first 6 months of life, this condition results in hazy corneas, larger eyes, sensitivity to light, and tearing. Usually caused by developmental abnormalities in the anterior chamber angle that disrupts the normal outflow of aqueous.
- Neovascular Glaucoma
Glaucoma caused by new blood vessel growth on the iris that extends over the fluid drainage area, thus blocking the outflow of aqueous. Usually associated with diabetes, this condition causes a painful swollen eye with elevated intraocular pressure.
- Phacolytic/lens Induced Glaucoma
Caused by a mechanical blockage of the eye's drainage route by lens proteins. This is associated with advanced (hypermature) cataracts, or trauma to the lens.
- Normal/low Tension Glaucoma
Type of open-angle glaucoma with all of the clasic glaucoma signs (progressive disc cupping, visual field loss) except for the increase in pressure. Intraocular pressure is low or normal in these patients.
- Pigmentary Dispersion Glaucoma
Another type of open-angle glaucoma. This is caused by pigment granules that break free from the iris and clog the fluid drainage route.
- Secondary Glaucoma
Resulting from a known cause such as inflammation, degeneration, trauma, or tumors in the eye.
Glaucoma can affect anyone. However, the risk of developing the disease is increased by factors such as:
- Family history
- High intraocular pressure (pressure in the eye)
- African descent
- Injury or trauma to the eye
- Prolonged steroid treatments
- Other medical conditions (e.g. diabetes, circulatory problems, blood pressure)
Detection and prevention are only possible with routine eye examinations. The exam will include a measure of the introcular pressure of both eyes, an evaluation of the optic nerve heads, and various other eye structures. Those who are glaucoma suspects may require additional testing (please see Glaucoma Testing section).
Most patients require an eye drop to control the pressure in the eyes. Occassionally, several medications are used to complement each other for better control of the intraocular pressures. In some cases surgery is indicated, in which the ophthalmologist will facilitate the drainage of fluid (aqueous) from the eyes.