Glaucoma is the second leading cause of blindness in the US and is the leading cause of blindless among Hispanics.
Glaucoma is a group of eye disorders leading to progressive damage to the optic nerve, (a bundle of about 1.2 million individual nerve fibers that transmits the visual signals from the eye to the brain), and is characterized by loss of nerve tissue resulting in loss of vision.
There are many types of glaucoma and many theories about the causes of glaucoma. The exact cause is unknown. One theory is that glaucoma is thought to develop when the eye’s drainage system becomes inefficient over time. This leads to an increased amount of fluid and a gradual buildup of pressure within the eye. Other theories of the cause of the optic nerve damage include poor perfusion, or blood flow, to the optic nerve. Damage to the optic nerve is slow and painless and a large portion of vision can be lost before vision problems are noticed.
Primary open-angle glaucoma
The most common form of glaucoma, primary open-angle glaucoma, develops slowly and usually without any symptoms. Many people do not become aware they have the condition until significant vision loss has occurred. It initially affects peripheral or side vision, but can advance to central vision loss. If left untreated, glaucoma can lead to significant loss of vision in both eyes, and may even lead to blindness.
Primrary open-angle glaucoma is associated with an increase in the fluid pressure inside the eye. This increase in pressure may cause progressive damage to the optic nerve and loss of nerve fibers. Vision loss may result. Advanced glaucoma may even cause blindness. Not everyone with high eye pressure will develop glaucoma, and many people with normal eye pressure will develop glaucoma. When the pressure inside an eye is too high for that particular optic nerve, whatever that pressure measurement may be, glaucoma will develop.
Acute angle closure glaucoma
A less common type of glaucoma, acute angle closure glaucoma, usually occurs abruptly due to a rapid increase of pressure in the eye. Its symptoms may include severe eye pain, nausea, redness in the eye, seeing colored rings around lights, and blurred vision.
This condition is an ocular emergency, and medical attention should be sought immediately, as severe vision loss can occur quickly.
It occurs when the drainage angle in the eye (formed by the cornea and the iris) closes or becomes blocked. Many people who develop this type of glaucoma have a very narrow drainage angle. With age, the lens in the eye becomes larger, pushing the iris forward and narrowing the space between the iris and the cornea. As this angle narrows, the aqueous fluid is blocked from exiting through the drainage system, resulting in a buildup of fluid and an increase in eye pressure.
This type of glaucoma occurs as a result of an injury or other eye disease. It may be caused by a variety of medical conditions, medications, physical injuries, and eye abnormalities. Infrequently, eye surgery can be associated with secondary glaucoma.
In this form of glaucoma, eye pressure remains within what is considered to be the “normal” range, but the optic nerve is damaged nevertheless. Why this happens is unknown.
It is possible that people with low-tension glaucoma may have an abnormally sensitive optic nerve or a reduced blood supply to the optic nerve caused by a condition such as atherosclerosis, a hardening of the arteries. Under these circumstances even normal pressure on the optic nerve may be enough to cause damage.
Glaucoma is diagnosed through a comprehensive eye examination. To establish a diagnosis of glaucoma, several factors must be present: Because glaucoma is a progressive disease, meaning it worsens over time, a change in the appearance of the optic nerve, a loss of nerve tissue, and a corresponding loss of vision confirm the diagnosis. Some optic nerves have a suspicious appearance, resembling nerves with glaucoma, but the patients may have no other risk factors or signs of glaucoma. These patients should be closely followed with routine comprehensive exams to monitor for change.
- Patient history to determine any symptoms the patient is experiencing and the presence of any general health problems and family history that may be contributing to the problem.
- Visual acuity measurements to determine the extent to which vision may be affected.
- Tonometry to measure the pressure inside the eye to detect increased risk factors for glaucoma.
- Pachymetry to measure corneal thickness. People with thinner corneas are at an increased risk of developing glaucoma.
- Visual field testing, also called perimetry, to check if the field of vision has been affected by glaucoma. This test measures your side (peripheral) vision and central vision by either determining the dimmest amount of light that can be detected in various locations of vision, or by determining sensitivity to targets other than light, and comparing it to others of similar age.
- Evaluation of the retina of the eye, which may include photographs of the optic nerve, in order to monitor any changes that might occur over time.
Supplemental testing may include gonioscopy, a procedure allowing views of the angle anatomy, the area in the eye where fluid drainage occurs. Serial tonometry may be performed. This is a procedure acquiring several pressure measurements over time, looking for changes in the eye pressure throughout the day. Other tests include using devices to measure nerve fiber thickness, and look for specific areas of the nerve fiber layer for loss of tissue.
Glaucoma cannot currently be prevented, but if diagnosed and treated early it can usually be controlled. Medication or surgery can slow or prevent further vision loss. However, vision already lost to glaucoma cannot be restored. That is why the American Optometric Association recommends an annual dilated eye examination for people at risk for glaucoma as a preventive eye care measure. Depending on your specific condition, your doctor may recommend more frequent examinations.
The treatment of glaucoma is aimed at reducing intraocular pressure. The most common first line treatment of glaucoma is usually prescription eye drops that must be taken regularly. In some cases, systemic medications, laser treatment, or other surgery may be required. While there is no cure as yet for glaucoma, early diagnosis and continuing treatment can preserve eyesight.
A number of medications are currently available to treat glaucoma. Typically medications are intended to reduce elevated intraocular pressure. One may be prescribed a single medication or a combination of medications. The type of medication may change if it is not providing enough pressure reduction or if the patient is experiencing side-effects from the drops.
Surgery involves either laser treatment, making a drainage flap in the eye, inserting a drainage valve, or destroying the tissue that creates the fluid in the eye. All procedures aim to reduce the pressure inside the eye. Surgery may help lower pressure when medication is not sufficient, however it cannot reverse vision loss.
Laser trabeculoplasty helps fluid drain out of the eye. A high-energy laser beam is used to stimulate the trabecular meshwork to work more efficiently at fluid drainage. The results may be somewhat temporary, and the procedure may need to be repeated in the future.
If eye drops and laser surgery aren’t effective in controlling eye pressure, you may need a filtering procedure called a trabeculectomy. Filtering microsurgery involves creating a drainage flap, allowing fluid to percolate into and later drain into the vascular system.
Another type of surgery, called drainage valve implant surgery, may be an option for people with uncontrolled glaucoma, secondary glaucoma or for children with glaucoma. A small silicone tube is inserted in the eye to help drain aqueous fluid.
By keeping eye pressure under control, continued damage to the optic nerve and continued loss of your visual field may slow or stop. Focus includes lowering the intraocular pressure to a level that is least likely to cause further optic nerve damage. This level is often referred to as the target pressure and will probably be a range rather than a single number. Target pressure differs for each person, depending on the extent of the damage and other factors. Target pressure may change over the course of a lifetime.
Newer medications are always being developed to help in the fight against glaucoma.
Who’s at risk
- Persons with a family history of glaucoma
- African Americans over the age of 40
- Hispanics over the age of 60
- Persons with chronic eye inflammation
- Persons using medications that increase the pressure in the eyes (including cortisteroids)
- Persons with thinner corneas
- Persons with eye injuries
- Asians and Japanese
- Those with a family history of glaucoma
What you can do
Early detection, prompt treatment and regular monitoring can help to control glaucoma and therefore reduce the chances of progressive vision loss.