Glaucoma
Glaucoma occurs when the drainage system in the eye becomes blocked, thus preventing the nourishing fluid that is constantly produced inside the eyeball from flowing out. As excessive amounts of this fluid build up inside the eyeball, there is an increase in pressure. This is called intraocular pressure because it is pressure inside the eye. In glaucoma, intraocular pressure rises to abnormally high levels. When intraocular pressure gets too high, or remains at high levels for too long, it can cause permanent damage to the retina and the optic nerve. Because the optic nerve carries all visual information to the brain, this can often result in the impairment or even total loss of vision.
There are two main types of glaucoma. Chronic, or open-angle, is the most common type, accounting for at least 90 percent of all cases. Chronic glaucoma progresses slowly over a long period of time. Excess fluid builds up in the eye, gradually raising the level of intraocular pressure. Usually there are no noticeable symptoms. This puts the patient's vision at risk because the pressure is likely to go untreated. Without treatment, it is common for people who have chronic glaucoma to have their vision clouded by halos and blind spots. The longer they go without treatment, the more likely they will lose their peripheral, and then their central or primary vision.
Most people with glaucoma require constant medical treatment to prevent their intraocular pressure from reaching dangerously high levels. Most doctors will prescribe pills or eyedrops to reduce the pressure. When these treatments prove inadequate, a doctor may recommend surgery.
Acute or closed-angle glaucoma is less common and usually more severe than chronic glaucoma. People with acute glaucoma experience extreme eye pain, headaches, nausea, and blurred vision. Surgical treatment is more commonly required to preserve eyesight. Marijuana is not considered to be as useful in treating this type of glaucoma because its progression is much more rapid and difficult to control. Nevertheless, some people with acute glaucoma find marijuana helpful in treating the pain and nausea they suffer.
In the past, many of the drugs routinely prescribed for glaucoma were inadequate or caused serious side effects in many patients. Eyedrops that were promoted as effective often failed to control intraocular pressure and sometimes increased the risk of hypertension, respiratory problems, reduced heart rate and even heart failure. Oral medications often caused nausea, vomiting, loss of appetite, headaches, kidney stones and blood disorders. Surgical procedures sometimes failed and needed to be repeated. They also involved some risk of serious complications, such as permanent damage to the eye and loss of vision.
It is well know that University of California researchers (Drs. Robert Hepler and Thomas Ungerleider) discovered marijuana could be useful for treating glaucoma, by accident in the 1970's, while carrying out a study for the Los Angeles Police Department. This assumption was commonly used by law enforcement in determining whether or not a suspected citizen was under the influence of marijuana. Each subject in the experiment was given federally grown marijuana and photographed while smoking. After smoking, they received ophthalmologic examinations. The photographs showed that rather than dilating, the subjects' pupils had constricted. The researchers also found that marijuana had reduced intraocular pressure and the production of tears.
There are many people suffering from glaucoma who were frustrated with their treatment options and chose to use marijuana as their medicine. They believe marijuana has helped them to maintain a low level of intraocular pressure and prevent further damage to their optic nerves. For some, marijuana has eliminated the appearance of halos and blind spots that impaired their vision. For others, marijuana relieved the pain that resulted from their glaucoma. Some patients have chosen marijuana simply because it is not painful or difficult to administer.
The current understanding is that THC constricts the capillaries in the eye, decreasing the rate of fluid secretion. This can explain why people who use marijuana often report a reduction in tears and a drying of the eyes. THC I also thought to expand the blood vessels in the mucous membranes that facilitate the drainage of fluid from the eye. This may explain why marijuana smokers often appear to have bloodshot eyes.
Orally administered THC (Marinol) cannot be prescribed for glaucoma, and has been found effective for reducing intraocular pressure only in very high doses under which patients have felt incapacitated and experienced unpleasant psychological effects.
As early as the late 1970's, there was interest in developing a THC solution that could be administered in drops to the surface of the eye. The idea was favored by ophthalmologists because a patient could apply THC without smoking it or experiencing any psychological effects. Unfortunately, no topical solution is yet available that would allow proper penetration and absorption of THC into the eye.
New prescription drugs have been developed, among them timolol (Timoptic) and lantanoprost (Xalatan), which are claimed to be highly effective with no side effects. Unfortunately, some patients are finding that these drugs do have side effects, or that they do not sufficiently reduce intraocular pressure. While Timoptic helps to reduce intraocular pressure in most cases, it can cause asthma and can affect heart rate and heart muscle function. This is an even more serious concern for patients over the age of 35, which includes most glaucoma patients. Xalatan can change the color of the eyes. Some patients who take these medications must still undergo numerous surgical procedures. Many doctors agree that the difficulties with these treatments probably result from the fact that patients vary both in their severity of intraocular pressure and their response to medication.
Science
