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Our guest glaucoma expert for this column today is Emily Chua Greenlee, M.D., Clinical Assistant Professor of Ophthalmology, University of Iowa Department of Ophthalmology & Visual Sciences, and Director of the Glaucoma Service at the Iowa City Veterans Administration Medical Center, who provided us vital information about this dreaded visual malady.
Next to cancer and heart disease, blindness ranks third as a major fear among people. Everyone is possibly at risk for glaucoma. One in 30,000 babies in the United States is born with this condition, and about 120,000 Americans are blind from glaucoma, roughly 10.5 percent of all blindness. Only half of the 3 million Americans with glaucoma know they have it. According to the World Health Organization, this eye disease is the second most common causes of blindness in the world. There are about 65 million people with glaucoma worldwide.
What is glaucoma?
Glaucoma is a disease of the optic nerve (optic neuropathy). Damage to the optic nerve leads to vision loss. This loss tends to be peripheral (side vision) which is why people tend not to notice it until it is very advanced. Vision loss can also be central. People with central vision loss come to medical attention much earlier because they notice their vision problem.
What causes optic nerve damage?
The optic nerve may be damaged by various causes. These are called optic neuropathies. The causes may be due to a lack of blood flow (ischemic optic neuropathy), inflammation (optic neuritis), infection, trauma (traumatic optic neuropathy), and toxic/metabolic causes. Glaucoma is one type of optic neuropathy.
Are there different types of glaucoma?
Yes. The main two types of glaucoma are open-angle and closed-angle glaucoma. These terms refer to the drainage angle of the eye which is located at the juncture of the cornea and iris. A person with glaucoma does not effectively drain this fluid (aqueous humor) from the eye.
In open-angle glaucoma, the angle is visualized to be open but for some reason, it is not draining aqueous humor effectively. This could be due to a problem with the angle. It could be ineffective from genetics, trauma, or something blocking the angle, such as blood or pigment.
In closed-angle glaucoma, the angle is blocked by the iris being pushed forward. This tends to happen in people with smaller eyes (farsightedness) or those developing cataracts. A cataract is the lens of the eye which becomes cloudy over time. As it progresses, it becomes thicker, and since it is located behind the iris, it can eventually block the drainage angle. Treatment is based on the type of glaucoma.
What are the signs and symptoms?
Usually, there are no signs and symptoms in open-angle glaucoma until vision loss becomes advanced. This is the reason why it is prudent to have a regular eye exam, especially among those 40 and over. Early diagnosis is essential to prevent optic nerve damage and blindness. Closed-angle glaucoma may present much more dramatically with sudden decreased vision and eye pain due to the sudden rise in intraocular pressure.
Who gets glaucoma?
The following are risk factors for open-angle glaucomas:
1.) Genetics plays a part. Patients with a family history of glaucoma are at risk for developing the disease.
2.) African descent. People of African descent are more likely to develop glaucoma and have more severe disease which is harder to treat.
3.) High eye pressure (intraocular pressure, IOP). Those with a high eye pressure are at risk for developing glaucoma. Most people without glaucoma have eye pressures < or = 21 mmHg. A high intraocular pressure is only a risk factor for glaucoma but is not required for the disease.
4.) Age > 40. As people age, the likelihood that they will develop glaucoma increases. Although there are some congenital (present at birth) and juvenile forms of glaucoma, most cases are adult.
5.) Thin corneas. The clear front part of the eye, or cornea, is what is touched when eye pressure measurements are made. If this is unusually thin, it may be easier to push against which creates an artificially low eye pressure reading.
The following are risk factors for closed-angle glaucomas:
1.) Hyperopia (farsightedness). People who are farsighted, or hyperopic, tend to have smaller eyes which puts them at risk for angle-closure.
2.) Age. As people age, their lenses of their eyes tend to develop into a cataract. As the cataract matures and thickens, it can cause angle-closure.
3.) Asian descent. Asians tend to have smaller eyes with the possibility of developing closed-angle glaucoma.
4.) Women. Women also tend to have smaller eyes, which predisposes them to this type of glaucoma.
What is the treatment for glaucoma?
Treatments for open-angle glaucomas aim toward lowering eye pressure since high eye pressure is a risk factor for the development of glaucoma. Numerous eye medications exist which lower the eye pressure by either lowering aqueous humor formation or facilitating its outflow from the eye. In addition, laser (Argon laser trabeculoplasty, selective trabeculoplasty) or incisional surgery (trabeculectomy, glaucoma drainage implantation) may be performed to increase aqueous outflow and lower eye pressure.
The treatment for closed-angle glaucoma is different, however. In this case, the treatment is aimed toward relieving the blockage of aqueous outflow. A laser procedure is performed which creates a small hole in the iris. This allows aqueous to come forward and prevents it from pushing the iris into the drainage angle. This laser procedure is called a laser peripheral iridotomy (LPI).
While there is no cure for glaucoma, it is essential that it be treated to prevent vision loss.
