Glaucoma is a group of diseases that affect the optic nerve, which connects the eye to the brain. It is a leading cause of vision loss and blindness in the United States and worldwide. It is the leading cause of blindness in working-age African-Americans.

Glaucoma can affect one or both eyes. It typically involves gradually increased pressure inside the eye, although some people with normal eye pressure can develop glaucoma.  It usually is gradual, painless and has no other signs or symptoms. There are also acute forms of glaucoma that are sudden, painful and a medical emergency.

The disease destroys peripheral (side) vision. Loss of eyesight is often so gradual it goes unnoticed until vision is significantly impaired. Any damage is irreversible, but diagnosis and treatment can avert further loss of vision.

There is an increased risk of glaucoma in people over age 60, diabetes patients, people with a family history of glaucoma and certain racial groups. Other risk factors include high blood pressure, eye injury and use of certain medications, such as corticosteroids.

Early detection and treatment can minimize or prevent eye damage. Tests to detect glaucoma include the dilated pupil examination, pachymetry (testing of corneal thickness), optic nerve tomography (scanning the optic nerve to judge its health) and tonometry (a measure of pressure inside the eye). Prescription eye drops can reduce the risk of developing glaucoma by about half. Other medications, laser therapy and surgery may also be options for treatment.

Glaucoma is a group of diseases affecting the optic nerve in one or both eyes. It involves internal eye (intraocular) pressure that is too high for the health of the patient’s eye. Glaucoma can impair vision or lead to blindness, but early detection and treatment can usually prevent serious damage.

Each optic nerve contains about 1.2 million nerve fibers in a cable-like structure that connects the retina to the brain. When the nerve fibers are damaged, the nerve impulses to the brain are thwarted and blind spots develop. Peripheral (side) vision can be reduced so that a person experiences tunnel vision. If untreated, the disease destroys the optic nerve and blindness results.

There is a space in the front of the eye called the anterior (front) chamber. It is filled with aqueous humor, a clear liquid containing nutrients. This fluid needs to flow freely in and out of the chamber to nourish the surrounding tissues. There is an angle where the cornea (clear tissue over the front of the eye) and iris (colored part of the eye around the pupil) meet. Here the fluid drains through a spongy drain called the trabecular meshwork and leaves the eye. If the fluid passes through too slowly, pressure builds. This pressure against the blood flow to optic nerve is believed to damage the nerve and destroy vision.

Having increased eye pressure does not mean someone has glaucoma but does increase the risk of developing the disease. Some individuals tolerate above-normal eye pressure. Conversely, some people with relatively low eye pressure develop glaucoma. This is called low-tension or normal-tension glaucoma.

A recent study known as the OHTS (Ocular Hypertension Treatment Study), showed that early treatment of patients who have high eye pressure reduces the risk of vision loss. The study also showed that patients with thinner corneas have higher pressures than those measured in the ophthalmologist’s office, and may constitute a large portion of the patients with normal-tension glaucoma. These findings have made corneal pachymetry (measurement of the thickness of the cornea) a routine part of a glaucoma examination.

The most common type of glaucoma, open-angle glaucoma, develops gradually and is largely symptomless. The patient will not notice any change in vision until the end stage of the disease when most vision is gone. Early detection of glaucoma is therefore crucial to preventing damage to the optic nerve and preserving vision. Regular eye examinations are necessary, especially for those with risk factors, including people over age 60, people with diabetes or high blood pressure, people with a family history of glaucoma, blacks and Hispanics.

Glaucoma is a major cause of vision loss and blindness in the United States and worldwide. Researchers have projected that the global number of glaucoma cases could hit 60 million by 2010 and 80 million by 2020. If glaucoma is detected and treated early, vision can often be saved. But lifetime monitoring and treatments are required.

Many types of glaucoma exist. Some have stronger hereditary links than others, meaning blood relatives of glaucoma patients should pay special attention to their family history and their own eye health. The types of glaucoma include:

• Open-angle glaucoma. Damage to the optic nerve (which connects the retina to the brain) caused by increased eye pressure due to poor drainage of aqueous humor (fluid inside the eye). The process is gradual and painless. Vision loss may be significant and irreversible by the time a problem is detected. This is the most common form of glaucoma. The risk of open-angle glaucoma increases with age, and heredity may be a factor. Varieties of open-angle glaucoma include:
  
  
• Normal-tension glaucoma (also called low-tension glaucoma). Optic nerve damage accompanied by normal or low eye pressure and eventual loss of vision. Often seen in patients with thin corneas. This form of glaucoma accounts for one-third of glaucoma cases in the United States, according to the Glaucoma Research Foundation.

This condition is not fully understood.  Experts believe that hypersensitivity in the optic nerve fibers or reduced blood flow to the optic nerve due to a variety of diseases leads to death of optic nerve cells. Below-normal pressure is required in such cases to prevent further nerve damage and loss of vision.

• Pigmentary glaucoma. Shedding of pigment from the iris (colored part of the eye) clogs drainage of the aqueous humor. This hereditary condition is found more often in myopic (nearsighted) people and men, according to the Glaucoma Foundation. The condition begins in the 20s and 30s, threatening eyesight at an early age.
  
  
• Angle-closure glaucoma (also called closed-angle or narrow-angle glaucoma). The aqueous humor is partially or totally blocked from draining by the iris. This uncommon condition sometimes involves an acute, painful attack that is a medical emergency requiring immediate treatment. If untreated, blindness can result within a day or two. Whereas most cases of glaucoma are painless and gradual, acute angle closure is typically excruciating and sudden. Often inherited, it is found more often among Asians and farsighted people, according to the Glaucoma Foundation.
  
  More common than acute angle-closure glaucoma is the chronic variation, in which the iris intermittently blocks the drainage, with fewer apparent symptoms. Both forms are treated surgically with a peripheral iridotomy treatment using a laser in the ophthalmologist’s office, office or, if necessary, surgically in an operating room.
  
  
• Congenital glaucoma. An inherited birth defect where the drainage angle of the eye is blocked by a membrane and slows the normal fluid drainage and increases eye pressure. Children with this birth defect will have cloudy eyes, large eyes (buphthalmos) or one eye bigger than the other. They may also have a lot of tearing and turn away from bright lights. In children under age 3, the eye pressure increases the size of the eyes. Surgery (goniotomy) performed promptly can sometimes spare vision.
  
  
• Secondary glaucoma. Acute or chronic glaucoma caused by trauma or related to another condition, such as diabetes or cataracts. In one kind of secondary glaucoma, neovascular glaucoma, new blood vessels proliferate from the iris and block the flow of water from the eyes.

Neovascular glaucoma is often associated with a type of diabetic retinopathy known as proliferative retinopathy (involving new blood vessels growing in and scarring the retina) and is strongly linked to diabetes. Neovascular glaucoma is painful, progresses rapidly and damages vision.

The underlying causes of glaucoma are unknown. There are genetic links to several types of glaucoma.  Contributing and risk factors include:

• Increased eye pressure. People with elevated pressure inside the eye (intraocular pressure) are more prone to, but do not always develop, glaucoma. In addition, some people with normal or low eye pressure develop the disease.
  
  
• Age and race. High-risk groups are blacks over age 40 and anyone over age 60, especially Mexican-Americans, according to the U.S. government's National Eye Institute. Asians are susceptible to angle-closure glaucoma. Japanese people are susceptible to normal-tension glaucoma.
  

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  Family medical history. A family history of glaucoma indicates increased likelihood of developing the disease.
  
  
• High blood pressure. Glaucomatous damage is exacerbated by above-normal blood pressure (hypertension).
  
  
• Diabetes. Elevated glucose (blood sugar), high blood pressure and heart disease related to diabetes all raise the odds of developing glaucoma. People with type 2 diabetes have higher rates of cataracts (clouding of the lens) and glaucoma leading to vision loss compared to the general population, in addition to their risk of diabetic retinopathy.
  
  
• Eye injuries. Severe physical trauma to the eye, burns from chemicals or penetrations can all lead to increased eye pressure, lens dislocations or blockage of drainage.
  
  
• Nearsightedness or farsightedness. Inability to see objects at far or close distances without glasses or contact lenses increases the likelihood of developing this disease.
  
  
• Prolonged use of corticosteroids.  Anti-inflammatory medication commonly used to prevent asthma, arthritis and allergy attacks. Secondary glaucoma is more likely in longtime users of corticosteroids, including cortisone. Longtime use of corticosteroids is also a risk factor for secondary diabetes, cataracts, osteoporosis and other conditions.
  
  
• Eye abnormalities. Structural eye abnormalities increase susceptibility to certain kinds of glaucoma, such as reduced thickness of the central cornea or narrow optic nerves.
  
  
• Pseudoexfoliation syndrome. A condition involving shedding of protein in the aqueous humor. Pigment and pseudoexfoliatiative material clogs the trabecular meshwork, elevating intraocular pressure. A whitish material builds up on the lens and can be seen by slit-lamp examination. This syndrome increases the risk of glaucoma (open-angle) by six times, according to the Glaucoma Foundation. Ten percent of people over age 50 have this syndrome, the organization reports.
  
  
• Other medical conditions. Migraines, poor circulation, retinal detachment, eye tumors and eye inflammations increase the risk of developing glaucoma. Some types of eye surgery may also lead to secondary glaucoma.

There are several types of glaucoma.  Signs and symptoms vary depending on which type the patient is experiencing.

Initially, no symptoms may be present with open-angle glaucoma (e.g., no pain or vision loss). As the disease progresses, peripheral (side) vision is affected, narrowing the field of vision like a tunnel until blindness occurs. Glaucoma can develop in one or both eyes. Usually, both eyes are affected.

An acute attack of angle-closure glaucoma can lead to permanent loss of vision within hours. It involves a rapid rise in eye pressure. These attacks often occur at dusk or dawn or in dark areas such as theaters. The following symptoms indicate a medical emergency requiring immediate treatment:

• Severe eye and head pain
• Blurred vision
• Perception of halos around lights
• Nausea and vomiting accompanied by eye pain
• Reddening of the eye

Neovascular glaucoma, a form of the disease that is strongly associated with diabetes, also is painful and develops quickly.

In children, signs of congenital glaucoma can include cloudy eyes, large eyes, one eye bigger than the other, excessive tearing or increased sensitivity to bright lights.

Regular eye examinations by an ophthalmologist are important in detecting glaucoma in time, before damage to the optic nerves takes place. The National Eye Institute advises a comprehensive eye examination every two years for high-risk individuals (black people older than 40, anyone over 60). Earlier or more frequent examinations may be recommended for people with additional risk factors, such as other eye conditions or diabetes.

Screening and tests to detect glaucoma may include:

• Tonometry. This painless test measures pressure inside the eye (intraocular pressure, IOP). Variations include air puff tonometry, in which the eye is numbed with drops and a puff of air is blown at it to measure the amount of air deflected by the eye. During applanation tonometry, the eye is numbed and a slit lamp (device emitting powerful light) illuminates the eye so the physician can examine it.  A small pressure-sensitive tip measures IOP by touching the surface of the eye. There is also a hand-held, pen-like tonometer that measures IOP without touching the cornea. Eye pressure that exceeds 21 millimeters of mercury (mmHg) indicates a risk for glaucoma.
  
  
• Visual field test (perimetry). Various tests, some using computer screens, assess any loss of peripheral (side) vision, a sign of glaucoma.
  
  
• Visual acuity test. This eye chart test is used to measure the acuity of vision.
  
  
• Dilated pupil examination. Drops are put into the eyes to enlarge the pupils. The inside of the eye is then examined for damage to the retina or to the optic nerve, a sign of glaucoma. After the exam, vision remains blurred for a short time.
  
  
• Funduscopy (ophthalmoscopy). Examination of the back of the eye (fundus) for damage. A funduscope, ophthalmoscope or biomicroscope is used to look through the pupil to the back of the inner eye. Any abnormal “cupping” or depression in the optic nerve can be seen along the back wall of the eye. A laser light and computer tomograph can re-create a three-dimensional image of the optic nerve, revealing changes that may indicate glaucoma.
  
  
• Gonioscopy. A special lens with an angled mirror is placed on the eye to inspect the drainage angle. This procedure can predict the likelihood of a patient having an acute angle-closure attack.
  
  
• Pachymetry. Test to measure the thickness of the cornea (the clear covering over the front of the eye). The eyes are numbed and tested with an ultrasonic wave instrument to gauge the thickness of the cornea. People with thin corneas can have glaucoma even if the pressure in the eye is low.
  
  
• Polarimetry. Scanning lasers measure the retinal nerve fiber layer.
  
  
• Other tests. These may include computerized imaging and photographing the optic nerve while the eyes are dilated. The images are then studied and compared over time for changes in the eye.

Damage from glaucoma is irreversible. Treatments focus on preventing further damage to the eyes. Patients should ask their ophthalmologist about the advantages, risks and side effects of treatment options.

Periodic (every three or four months) and thorough examination is crucial to the prevention of further eye damage and loss of vision. For patients who have already lost some of their vision, low-vision services may be an option to help them compensate and to help maintain remaining sight.

Medications used to treat glaucoma include:

• Eye drops. Prescription eye drops reduce intraocular pressure by decreasing the production of aqueous fluid or improving the flow of fluid through the drainage angle or other outflow areas. Eye drops, typically applied daily or several times a day, are a common and usually effective treatment for glaucoma and have been found to delay and even prevent the onset of glaucoma. The patient should follow instructions and not skip drops because damage to the optic nerves can occur if eye drops are not applied properly.
  
  
  Classes of eye drops include prostaglandins, adrenergics, miotics, beta blockers and carbonic anhydrase inhibitors. A physician can advise about possible side effects. Physicians may avoid prescribing certain types to people with diabetes. Beta blockers, a type of antihypertensive, can interfere with control of glucose (blood sugar) and may be a risk factor for secondary diabetes. The National Institutes of Health cautions that carbonic anhydrase inhibitors, a type of diuretic, may cause hyperglycemia and worsen kidney disease. It advises diabetic patients who are prescribed these drugs to be vigilant with glucose monitoring and report any problems to their physician.

• Oral medications and injections. Carbonic anhydrase inhibitors and a class of drugs called hyperosmotics can be taken by mouth and, for glaucoma emergencies, may be injected. Hyperosmotics, like carbonic anhydrase inhibitors, may be contraindicated for people with diabetes.

Researchers have found that some patients who respond poorly to one glaucoma medication may benefit from a combination therapy.

Some patients report relief from smoking marijuana. About a dozen U.S. states have laws supporting medical use of marijuana, but the federal government has banned it. According to the Food and Drug Administration (FDA), there is no scientific evidence for medical use of marijuana, but there is proof of harmful effects from smoking marijuana. Research into cannabinoids (marijuana-like medications, including extracts applied beneath the tongue) as a potential treatment for glaucoma, pain and other conditions continues.

Surgery is recommended if it is needed to prevent further optic nerve damage or if medication is ineffective or not tolerated by the patient. Possible complications of surgical procedures include infection, loss of vision, scarring, development of cataracts, swelling (edema), bleeding or undesired changes in eye pressure.

Surgery can be either laser (photocoagulation) or conventional:

• Argon laser trabeculoplasty. An outpatient laser procedure used to modify the trabecular meshwork (drain) to help control eye pressure by allowing fluid to drain from the eye. This procedure is used for open-angle glaucoma. First, numbing drops are applied to the eye.  Then several burns are made in the trabecular meshwork using a high-intensity beam of light aimed at the lens and reflected onto the meshwork. In this way the drainage space is enlarged and the eye pressure is reduced.
  
  This laser treatment is applied to one eye at a time and may take several weeks to treat the other eye. Also, it may be performed in two sessions per eye. According to the Glaucoma Research Foundation, it is 75 percent effective. The benefits of the procedure may be temporary and in some cases last only two years. Repeat procedures are usually ineffective. Glaucoma medication should still be taken after this procedure.
  
  There is a newer form of this procedure, selective laser trabeculoplasty (SLT), that uses a different laser and may cause less scarring and have better results. Recent research suggests that when trabeculoplasty needs to be repeated, SLT may produce better results than the argon procedure.

• Cyclophotocoagulation. A laser procedure used to destroy parts of the ciliary body to reduce its production of aqueous humor (fluid in the eye). This procedure is used in advanced or severe cases of glaucoma, in eyes with minimal or no vision, to reduce the eye pressure.
  
  
• Filtering microsurgery. An outpatient surgical procedure used to create a new drainage channel in the eye for the aqueous fluid to leave the eye. After the eye area is numbed, a small piece of tissue is removed to create a new area for the fluid to drain from. Types of filtering microsurgery include trabeculotomy in adult glaucoma and goniotomy in congenital glaucoma. The patient applies eye drops after surgery to prevent infection.
  
  This procedure is performed on one eye at a time and is scheduled four to six weeks apart for each eye. The success rate is 60 to 80 percent in lowering eye pressure, according to the National Eye Institute. A second operation may be required if the opening narrows from scarring. Possible side effects include infection, cataracts, bleeding or decreased visual acuity.
  
  
• Nonpenetrating surgery. Techniques developed as less-invasive potential alternatives to trabeculotomy in draining excess fluid. These include canalostomy, viscocanalostomy and deep sclerectomy.
  
  
• Drainage devices. A special plastic or collagen tube or shunt can be surgically implanted into the eye to absorb excess aqueous fluid and lower eye pressure. Such devices may be considered when other treatments have failed.
  
  
• Iridotomy. An outpatient procedure performed to stop a chronic or acute closed-angle attack of glaucoma. This is an emergency procedure performed by an ophthalmologist, who uses a combination of eye drops to constrict the pupil and provides the patient with medication to reduce the eye’s fluid production. Under anesthesia, a laser beam is used to create a small opening in the iris (colored part of the eye) to allow drainage of fluid through the trabecular meshwork. This may be done as a preventive measure for the unaffected eye as well. 

Some medications, including corticosteroids, vasoconstrictors (such as decongestants and antihistamines, including those in some eye drops), anticholingergics (e.g., bronchodilators, drugs for overactive bladder, drugs for Parkinson’s disease), antidepressants and anti-anxiety agents, have warnings for glaucoma patients. With some of these, precautions apply only for certain types of glaucoma. People who have or are at risk for glaucoma are advised to consult their ophthalmologist about which prescription medications, over-the-counter drugs and supplements they may safely use and which they should limit or avoid.

Early detection and treatment of glaucoma can significantly lower the chances of developing glaucoma and its resulting loss of vision. Physicians of patients at higher risk, such as patients over 60, people with diabetes, people with a family history of glaucoma, African-Ameticans, Hispanics or people who are on corticosteroid therapy, may recommend comprehensive eye examinations every year or sometimes more frequently. Patients diagnosed with glaucoma should take their medication as prescribed and continue to see their eye care specialist regularly.

Scientists at the U.S. government’s National Eye Institute found that eye drops used daily for lowering eye pressure delayed and reduced the development of primary open-angle glaucoma in black Americans as much as 50 percent. This is a significant finding because primary open-angle glaucoma is the nation’s most common form of glaucoma and a leading cause of blindness.

According to the American Academy of Ophthalmology, the recommended schedule for comprehensive eye exams in patients without any eye disease is as follows:

• Age 20-29. Individuals of African descent and those with a family history of glaucoma should have an eye exam every three to five years. Others should have an eye exam at least once during this period.
  
  
• Age 30-39. Individuals of African descent and those with a family history of glaucoma should have an eye exam at least every two to four years. Others should have an eye exam at least twice during this period.
  
  
• Age 40-64. Every two to four years.
  
  
• Age 65 and older. Every one to two years.

Patients who are diagnosed with glaucoma should inform blood relatives of their condition to alert them to their own potential for developing the disease. Blood relatives should be encouraged to get a comprehensive eye examination at least once every two years. Some insurance plans, including Medicare, cover high-risk individuals for comprehensive eye exams to screen for glaucoma.

Research has shown that exercise may reduce the risk of glaucoma. It also helps control diabetes and high blood pressure, two of the risk factors for glaucoma. People are advised not to hold in their breath during resistance activities such as lifting weights, which may increase intraocular pressure.

A great deal of research is being conducted in the diagnosis, treatment and prevention of glaucoma. Among the recent developments:

• The Ocular Hypertension Treatment Study has sparked creation of a glaucoma risk calculator.
  
  
• An online tool has been developed to screen people for glaucoma risk.
  
  
• The National Eye Institute is funding research to improve glaucoma testing.
  
  
• German researchers report that measuring the velocity of circulation in arteries of the eye can indicate which glaucoma patients are at greatest risk of advanced disease.
  
  
• Some research has found selective laser trabeculoplasty, a newer variation on argon laser trabeculoplasty, to be effective.
  
  
• Pneumatic trabeculoplasty, a potential alternative to surgery that uses suction in an effort to lower pressure inside the eye, is being studied.
  
  
• Medications under development include a compound that suppresses an enzyme called Rho-kinase (ROCK) and a compound that incorporates nitric oxide. Monoclonal antibodies and marijuana-like cannabinoids are also being studied. To address concerns that many glaucoma patients have difficulty applying or are otherwise not taking their eye drops, researchers are investigating oral medications and ocular injections.
  
  
• The discovery of a previously unknown growth factor called oncomodulin might eventually lead to treatments that reverse damage to the optic nerve, according to scientists in Boston.
  
  
• Researchers at Harvard Medical School have reported regenerating a rodent optic nerve and have expressed hope that stem cells may in the near future allow regeneration of human optic nerves and retinas.
  
  
• Gene therapy researchers have reported some success in slowing the death of eye cells by using a virus to insert genes into the eyes of lab rats with glaucoma.
  
  
• Researchers have developed a genetic test using a sample of saliva that can reveal risk for an aggressive form of primary open-angle glaucoma.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about glaucoma:

1. How much does having diabetes increase my risk of glaucoma?
   
   
2. Do I have high blood pressure or other additional risk factors for glaucoma?
   
   
3. If a relative has glaucoma, am I at high risk?
   
   
4. How can I reduce my chances of getting glaucoma?
   
   
5. How often should I have an eye exam? What should it include?
   
   
6. What are the results of my eye exam? Do I have, or am I at risk of, glaucoma?
   
   
7. Have I lost any vision? What is my prognosis for preserving vision?
   
   
8. Which medications can help me?
   
   
9. Do any recommended glaucoma treatments alter blood sugar or otherwise affect my diabetes?
   
   
10. At what point might I need surgery? If surgery is necessary, what does it involve?
    
    
11. How will my condition and treatments be monitored?
    
    
12. If I would benefit from low-vision services, what is available to me, and what do you recommend?
    
    
13. Can I help prevent or control glaucoma through exercising, reducing high blood pressure or other means?