What is Glaucoma?
Glaucoma is a condition of the eye characterized by damage to the optic nerve that is usually caused by excessive pressure within the eye, or intraocular pressure (IOP). Glaucoma is actually a group of diseases composed of over twenty different forms. Left untreated, any of these forms of glaucoma will result in permanent progressive vision loss that can eventually lead to blindness.
Glaucoma is the leading cause of preventable blindness in the United States, afflicting over two million Americans. It is estimated there are about 80,000 individuals who are legally blind in the U.S. due to glaucoma. Glaucoma is particularly hard hitting in the African-American community, where it is the leading cause of blindness. Glaucoma is found most commonly in the elderly, but it has the capability of affecting folks of any age, even newborns or fetuses in some instances.
The good news is that glaucoma can be easily diagnosed, and when caught early most vision loss can be avoided. There are also a variety of treatments available, both mainstream medical and alternative.
What Causes Glaucoma?
To me, the eye is one of the most amazing organs of the body. The complexity of its design is truly a wonder of engineering. To better understand the ins and outs of glaucoma, it may help to have some basic knowledge of the structure of the eye.
Intraocular Pressure (IOP) is the mechanism whereby the eye is able to maintain its spherical shape. A good analogy might be a balloon. Too much air pressure can strain the shape of a balloon, and even cause it to pop. In optical terms, abnormally high IOP causes damage to the optic nerve, which is actually a bundle of over one million nerve fibers that is the main pipeline for the eye to transport images to the brain. IOP is regulated by certain fluids found inside the eye, sort of like the affect of hydraulic fluid in some machinery.
The eye is composed of several layers. The sclera is a protective covering that encompasses the entire eye while allowing light to enter through the cornea at the front of the eye, and electrical impulses to exit via the optic nerve at the rear. Light that enters the cornea must pass through the iris before it reaches the lens. The iris is able to control the amount of light that is let in by adjusting the size of a structure within it called the pupil, which functions somewhat like the diaphragm of a camera.
Thanks for bearing with my lecture, because now we’re getting to the nitty-gritty of glaucoma. As I mentioned above, IOP is maintained by the presence of fluids within the eye. The iris, cornea, and lens are bathed in a fluid called the aqueous humor, which occupies the front of the eye. The other important fluid found in the eye is called the vitreous, and it fills the vitreous cavity found at the rear of the eye. The aqueous humor is continually produced by the eye, so there is also a complex drainage system involved that is responsible for channeling the fluid out of the eye at the proper rate in order to keep the IOP normal. The drainage mechanism is composed of a network of very intricate channels called the trabecular meshwork that eventually draws off the aqueous humor into a structure known as Schlemm’s canal where it is dumped into the bloodstream. Glaucoma is the result of too much aqueous humor, either from abnormal amounts of production, or inadequate drainage to rid it from the eye. This excess fluid increases the IOP to levels that cause damage to the optic nerve and result in eventual vision impairment if left unchecked.
There are two main types of glaucoma:
- Primary open-angle glaucoma, or chronic open-angle glaucoma as it is sometimes called, is the most commonly found form, accounting for over 90% of all glaucoma cases. It is referred to as “open-angle” because the space or angle between the iris and cornea is open, allowing for drainage of the aqueous humor. However, IOP still climbs to abnormal levels in open-angle cases, but it is a chronic condition that usually causes slow but steady damage to the optic nerve over time, resulting in the associated vision problems.
- Acute angle-closure glaucoma, or closed-angle glaucoma, is much less common, but due to its acute nature, can be a sudden and serious medical emergency that needs immediate attention. With closed-angle glaucoma, the access for drainage of the aqueous humor is suddenly blocked, causing a spike in IOP, which can cause permanent vision loss within 24 hours of an attack if it is not treated properly. There are several causes for this. Researchers believe that some people are born with a genetic defect that leaves them with an abnormally narrow drainage angle. As we age, the lenses of our eyes tend to get larger, and this may narrow the gap between the iris and cornea and cause angle-closure problems that lead to excessively high IOP. Angle-closure glaucoma can also come on suddenly due to a trauma or injury to the eye that pushes the iris too close to the trabecular meshwork and blocks drainage of the aqueous humor.
Another factor to be aware of is the affect some medicines can have on your eyes, especially if you are born with unusually narrow angles for drainage. Certain drugs such as antihistamines, tricyclic antidepressants, and some eye drops can cause dilation of the pupils, which has been known to set off an attack of angle-closure glaucoma in some folks. Eye drops which cause the pupils to dilate suddenly can cause immediate glaucoma attacks, or my not cause the angle to close for several hours after the use of the drops. As always, don’t assumeanything regarding the safety of any medication, whether it is prescribed or over the counter. Being informed can save your vision, or in some cases your life!
What Are the Symptoms of Glaucoma?
Typical symptoms will vary depending on the type of glaucoma:
- Open-angle glaucoma normally progresses slowly, and may have no symptoms or very minor ones until it has progressed into the advanced stages. This can make it a very dangerous form. Many patients, if they do not get regular eye exams, will never know they have glaucoma until it is too late and inevitable blindness will result. Sometimes symptoms will affect only one eye at first, but eventually both eyes will be damaged. Peripheral vision is usually compromised first, then tunnel vision may occur, and eventually total blindness.
- Closed-angle glaucoma occurs suddenly, and most often happens in low-light conditions such as at twilight or in a darkened room with poor lighting. Unlike open-angle, symptoms are distinct and may be severe:
ü Sudden and unexpected pain, which may be intense
ü Extreme reddening of the eye
ü Blurry vision
ü The appearance of halos around lights
ü Closed-angle attacks require immediate care to avoid permanent vision loss. While the attack may show itself initially in only one eye, both are eyes are in danger.
- Low-tension glaucoma: This is a poorly understood form of glaucoma whereby the IOP is not abnormally high, yet damage occurs to the optic nerve anyway. Some researchers speculate it may have something to do with reduced blood supply to the optic nerve that can occur as a result of arteriosclerosis, or “hardening of the arteries” as it is commonly called.
What Are the Risk Factors Associated With Glaucoma?
Increased intraocular pressure is the common trait that causes most cases of glaucoma, but not everyone who has elevated IOP will develop glaucoma. There are many factors that can increase a person’s risk for this illness:
- Age: This is the largest contributing factor to risk for glaucoma. Chances of developing glaucoma increase for all of us when we hit 60. For African-Americans it is higher after the age of 40.
- Race: Glaucoma is found three times as often in the African-American community as it is amongst Caucasians. Their risk for permanent blindness is much greater too. Hispanics have a higher incidence than Caucasians also, but not as high as African-Americans. Asian-Americans and Japanese-Americans are also more susceptible to certain forms of glaucoma, angle-closure and low-tension respectively. The reasons for this racial disparity are not known.
- Genetics: More than 20 genes have been identified as possibly being associated with increased risk for glaucoma. Statistics prove that if you have a close family member with a history of glaucoma, your risk is significantly increased of developing it yourself.
- Other medical conditions: Hypertension, diabetes, and coronary disease are three of the most common maladies that increase risk for glaucoma.
- Eye injuries: Any trauma to the eye can increase risk of glaucoma, such as a detached retina, eye surgery, eye tumors, or inflammatory eye diseases such as uveitis or iritis.
- Nearsightedness: For reasons not well understood, if you cannot see far away objects clearly without corrective lenses, your risk for glaucoma is greater.
- Corticosteroids: Prolonged use of these drugs has a side effect of increasing your chances of getting glaucoma.
- Coffee: Attention All Coffee Drinkers! It has been discovered that regular use of coffee leads to slightly increased IOP in some folks. This is not a major risk factor, just thought I’d throw it in as another good reason for quitting the coffee habit.
What Can I Do to Prevent or Treat Glaucoma?
The best recommendation I can make regarding this question, other than avoiding any risk factors that you can, is to get regular eye checkups from an optometrist or an ophthalmologist that include checking for glaucoma. There are routine tests (you’re probably familiar with the “air-puff” one called a tonometry) that can easily diagnose glaucoma. The earlier glaucoma is discovered, the less chance it has of damaging your vision.
If you are diagnosed with glaucoma, there are medicines that are commonly prescribed. Just be aware that like anything foreign that goes into your body, there are potential side effects that your doctor may not tell you about, or even more frighteningly, may not even be aware of.
Many folks have found that a diet rich in vitamins C, B1, chromium, zinc, and the flavonoid rutin has had a positive effect at lowering IOP. Even marijuana has been shown to lower IOP in some studies. But don’t run out and track down a pot dealer just yet. Marijuana has some serious side effects of its own that may not be worth the risk. As with all health matters, use common sense, educate yourself, and don’t believe everything your M.D. tells you.