Glaucoma is a group of eye disorders leading to progressive damage to the optic nerve, and is characterized by loss of nerve tissue resulting in loss of vision. Glaucoma occurs when internal pressure in the eye increases enough to cause damage to the optic nerve, leading to loss of nerve tissue, resulting in vision loss.
Glaucoma - often called "the sneak thief of sight" because it can strike without pain or other symptoms, and is one of the leading causes of blindness in the United States. Unfortunately, the vast majority of Americans - 91% - incorrectly believe glaucoma is preventable. Although glaucoma is not preventable, if diagnosed and treated early, a patient can control the disease. Medication or surgery can slow or prevent further loss of vision.
What causes glaucoma?
Clear liquid, called the aqueous humor, flows in and out of the eye. This liquid is not part of the tears on the outer surface of the eye. You can think of the flow of aqueous fluid as a sink with the faucet turned on all the time.
If the drainpipe gets clogged, water collects in the sink and pressure builds up. If the drainage area of the eye...called the drainage angle...is blocked, the fluid pressure within the inner eye may increase, which can damage the optic nerve.
What are the different types of 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.
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.
Secondary glaucoma - This type of glaucoma occurs as a result of an injury or other eye disease. It may be caused by a variety of medical conditons, medications, physical injuries, and eye abnormalities. Infrequently, eye surgery can be associated with secondary glaucoma.
Normal-tension 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 conditon such as atherosclerosis, a hardening of the arteries. Under these circumstances even normal pressure on the optic nerve may be enough to cause damage.
What are the risk factors?
Certain factors can increase the risk for developing glaucoma. They include:
- Age - People over age 60 are at increased risk for the disease. For African Americans, however, the increase in risk begins after age 40. The risk of developing glaucoma increases slightly with each year of age.
- Race - African Americans are significantly more likely to get glaucoma than are Caucasians, and they are much more likley to suffer permanent vision loss as a result. People of Asian descent are at higher risk of angle-closure glaucoma and those of Japanese descent are more prone to low-tension glaucoma.
- Family history of glaucoma - Having a family history of glaucoma increases the risk of developing glaucoma.
- Medical conditions - Some studies indicate that diabetes may increase the risk of developing glaucoma, as do high blood pressure and heart disease.
- Physical injuries to the eye - Severe trauma, such as being hit in the eye, can result in immediate increased eye pressure and future increases in pressure due to internal damage. Injury can also dislocate the lens, closing the drainage angle, and increasing pressure.
- Other eye-related risk factors - Eye anatomy, namely corneal thickness and optic nerve appearance indicate risk for development of glaucoma. Conditions such as retinal detachment, eye tumors, and eye inflammations may also induce glaucoma. Some studies suggest that high amounts of nearsightedness may also be a risk factor for the development of glaucoma.
- Corticosteroid use - Using corticosteroids for prolonged periods of time appears to put some people at risk of getting secondary glaucoma.
How is glaucoma diagnosed?
Glaucoma is diagnosed through a comprehensive, dilated 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, dilated eye 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 of 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 change that might occur over time.
- Evaluation of the retinal nerve fiber layers, which is performed using the OCT or GDX, in order to monitor any change in the retinal nerve fiber layers 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 occures. 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.
How is glaucoma treated?
The treatment of glaucoma is aimed at reducing intraocular pressure. The most common first line of 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.
- Medications - 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 ceates the fluid in the eye. All procedures aim to reduce the pressure inside the eye. Surgery may help lower presure when medication is not sufficient, however it cannot reverse vision loss.
- Laser surgery - 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.
- Conventional surgery - if eye drops and laser surgery aren't effective in controlling eye pressure, you may need a filtering procuedure called a trabeculectomy. Filtering microsurgery involves creating a drainage flap, allowing fluid to percolate into and later drain into the vascular system.
- Drainage implants - another type of surgery, called drainage valve implant surgery, many 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.
Canaloplasty - a new alternative
A canaloplasty procuedure might be the optimal choice for patients whose medications aren't working but aren't quite ready to take on the risks of surgery. It may also be optimal for patients whose medications are working but are frustrated with the frequency of dosing.
Canaloplasty is an advanced, nonpentrating procedure designed to enhance and restore the eye's natural drainage system to provide sustained reduction of intra-ocular pressure. Canaloplasty utilizes breakthrough microcatheter technology in a simple and minimally invasive procuedure.
Treatment for acute angle-closure glaucoma
Acute angle-closure glaucoma is a medical emergency. Several medications can be used to reduce eye pressure as quickly as possible. A laser procedure called laser peripheral iridotomy will also likely be performed. In this procedure, a laser beam creates a small hole in the iris to allow aqueous fluid to flow more freely into the front chamber of the eye where it then has access to the meshwork for drainage.
Glaucoma management is a lifelong process that requires frequent monitoring. Since there is no way to determine if glaucoma is under control based on how a patient feels, someone with glaucoma generally should be examined every 3 to 4 months.