What is Glaucoma
Glaucoma is caused by a number of different eye diseases which in most cases produce increased pressure within the eye. This elevated pressure is caused by a backup of fluid in the eye. Over time, it causes damage to the optic nerve. Through early detection, diagnosis and treatment, you and your doctor can help to preserve your vision.
Think of your eye as a sink, in which the faucet is always running and the drain is always open. The fluid in your eye, aqueous humor, is constantly circulating through the anterior chamber. It is produced by a tiny gland, called the ciliary body, situated behind the iris. It flows between the iris and the lens and, after nourishing the cornea and lens, flows out through a very tiny spongy tissue, only one-fiftieth of an inch wide, called the trabecular meshwork, which serves as the drain of the eye. The trabecular meshwork is situated in the angle where the iris and cornea meet. When this drain becomes clogged, aqueous can not leave the eye as fast as it is produced, causing the fluid to back up. But since the eye is a closed compartment, your `sink´ doesn't overflow; instead the backed up fluid causes increased pressure to build up within the eye. We call this open (wide) angle glaucoma.
To understand how this increased pressure affects the eye, think of your eye as a balloon. When too much air is blown into the balloon, the pressure builds, causing it to pop. But the eye is too strong to pop. Instead, it gives at the weakest point, which is the site in the sclera at which the optic nerve leaves the eye.
The optic nerve which carries visual information to the brain is made up of over one million nerve cells, and while each cell is several inches long, it is extremely thin. When the pressure in the eye builds, the nerve cells become compressed, causing them to become damaged and, eventually die. The death of these cells results in permanent visual loss. Early diagnosis and treatment of glaucoma can help prevent this from happening.
In the United States, approximately 2.2 million people age 40 and older have glaucoma, and of these, as many as 120,000 are blind due the disease. The number of Americans with glaucoma is estimated to increase to 3.3 million by the year 2020. Vision experts estimate that half of those affected may not know they have it because symptoms may not occur during the early stages of the disease. Glaucoma is a leading cause of blindness among African Americans and Hispanics in the United States . African Americans experience glaucoma at a rate of three times that of Caucasians and experience blindness four times more frequently. Between the ages of 45 and 64, glaucoma is fifteen times more likely to cause blindness in African Americans than in Caucasians.
Adult glaucoma falls into two categories – open angle glaucoma and closed angle glaucoma. These categories are subdivided, according to whether the cause is unknown (primary glaucoma) or known i.e. the high eye pressure is caused by other conditions of the eye (secondary glaucoma).
What are the symptoms
Normal-tension glaucoma (also termed normal-pressure glaucoma, low-tension glaucoma or low-pressure glaucoma) is an open-angle type of glaucoma that can cause visual field loss due to optic nerve damage, but in normal-tension glaucoma, the eye's Intra-Ocular Pressure (IOP) remains in the normal range.
Chronic narrow-angle glaucoma, like open-angle glaucoma, can be symptom less until vision loss occurs.
Symptoms of chronic glaucoma following an eye injury could indicate secondary glaucoma.
Acute angle-closure glaucoma is a medical emergency. If the high pressure is not reduced within hours, it can permanently damage vision.
An acute attack of narrow-angle glaucoma, also termed acute angle-closure glaucoma or acute closed-angle glaucoma, produces sudden symptoms such as eye pain, headaches, haloes around lights, dilated pupils, vision loss, red eyes, nausea and vomiting. These signs may last for a few hours, then return again for another round. Each attack takes with it part of your field of vision.
Other signs include headaches, blurred vision, difficulty adapting to darkness, or haloes around lights. Chronic glaucoma normally develops after age 35.
Anyone who experiences its symptoms should immediately contact an ophthalmologist or go to a hospital emergency room.
Pigmentary glaucoma often exhibits no symptoms at all. You may notice some pain and blurry vision after exercise. Pigmentary glaucoma affects mostly white males in their mid-30s to mid-40s.
It's difficult to spot signs for congenital glaucoma because children are too young to understand. If you notice a cloudy, white, hazy, enlarged or protruding eye, consult your eye doctor. Congenital glaucoma occurs more in boys than girls.
What causes Glaucoma
Glaucoma is caused by a number of different eye diseases and conditions which in most cases produce increased pressure within the eye. Also certain drugs and drug combinations are known to be possible causes of Glaucoma.
- Eye surgery
- Advanced Cataracts
- Eye Injury
- Eye tumors
- Uveitis (eye inflammation)
- Auto-immune Uveitis
- Marfan Syndrome
- Sturge-Weber Syndrome
- Iridocorneal Endothelial Syndrome
How is Glaucoma diagnosed
A physical examination of the eye may be used to diagnose glaucoma, but because intraocular pressure fluctuates, examination of the junction of the optic nerve and the retina with an instrument called an ophthalmoscope is necessary.
A standard ophthalmic examination may include:
Intraocular pressure measurement by tonometry
Visual field measurement
Pupillary reflex response
Slit lamp examination
How can Glaucoma be treated
Currently, there is no cure for glaucoma, but treatment can control the progression of the disease. The primary goal of treatment is to prevent further damage to the eye by lowering intraocular pressure (IOP) and to ultimately prevent blindness. Treatment of glaucoma may include medications, surgery, or a combination of medication and surgery.
For open angle glaucoma, topical eye medications (eye drops, gels and ointments) are often used early in the disease followed by oral medications or surgery. Surgery is frequently used in individuals who do not experience adequate lowering of intraocular pressure by the medications or in individuals who experience unwanted side effects from using medications. For closed-angle glaucoma, laser surgery is often performed before a doctor prescribes medications. But, glaucoma medications may also be given after the surgery.
Topical beta-blocking eye medications are commonly used as initial therapy for the treatment of open-angle glaucoma. Additional agents may be added to the beta-blocker if the intraocular pressure (IOP) remains elevated. The choice of the second medication often depends on how well the drug is tolerated, how well it works, and its ease of use. It is important to know that it is possible to require up to four different topical medications to treat glaucoma.
There are several types of topical medications that are used for the treatment of glaucoma. These medications work to lower intraocular pressure (IOP) by either decreasing the amount of aqueous fluid the eye makes or by helping the aqueous fluid drain from the eye. The topical eye drops, gels or ointment may cause burning, stinging, or redness when instilled into the eye, although these side effects are usually tolerable. If you have problems using one topical eye medication, tell your doctor or pharmacist because using a different drug or dosage may be possible.
Medications can be taken by mouth when topical eye medications are not effective at controlling or reducing intraocular pressure (IOP). Medications by mouth may also be used alone or in combination with topical eye medications to lower the pressure. Oftentimes patients experience more side effects with the medications taken by mouth than with topical eye medications.
The following drug classes are used to treat Glaucoma:
- Carbonic Anhydrase Inhibitors
- Carbonic Anyhydrase Inhibitor and Beta-Blocker Combination
- Prostaglandin Analogues
Although the present generation of medications for glaucoma can help control the disease, most have side effects, and none, so far, can provide a cure. As a result, research is ongoing, as scientists attempt to devise more effective tactics to fight the disease.