Ask an Expert about Glaucoma

Unfortunately, the answer is not any single number. While the average eye pressure is approximately 15, the range of normal eye pressure is much larger. About 90 percent of people will fall between a pressure of 10 and 21. Even so, this does not mean that if you have a pressure of 22 or higher it is abnormal. Every individual and every eye is different. There are many patients with pressures in the mid-20s who do not have glaucoma, and they can be followed with routine eye examinations by their eye care specialist. There are also patients who have been diagnosed with glaucoma and yet, even though treatment may decrease their pressure below 22, they still experience worsening of their glaucoma.

It is important that you see an eye care specialist to receive a thorough examination and determine if your eye pressure is problematic.

The BrightFocus National Glaucoma Research website goes into greater depth on many topics and covers additional areas of concern, both medical and social. You can learn where to get help and access to resources, as well as download free publications. And explore our Ask an Expert section where you can read or post queries to doctors. For more information dealing with the topics below, please visit the helpful organizations section of our website.

• Clinical Trials
• Organizations of Eye-care Professionals
• Federal Government Programs and Services
• General Information, Resources and Referrals
• Legal Assistance
• Low Vision Aid Resources
• Low Vision Organizations
• Print and Audio Materials for the Visually Impaired
• Senior Housing
• State and Local Resources

When a patient has glaucoma or is at high risk for developing the disease, physicians may document changes over time in the optic nerve through imaging techniques including stereo optic nerve photographs, scanning laser polarimetry (GDx), confocal scanning laser ophthalmoscopy (Heidelberg Retinal Tomograph or HRT II) and optical coherence tomography (OCT). An eye care professional will determine which method(s) to use.

Glaucoma is actually a group of eye diseases that lead to damage of the optic nerve (the bundle of nerve fibers that carries information from the eye to the brain), which can then lead to vision loss and possibly blindness. Optic nerve damage usually occurs in the presence of high eye (intraocular) pressure; however, it can occur with normal or even less than normal eye pressure. More than three million Americans are living with glaucoma, 2.7 million of whom—aged 40 and older—are affected by its most common form, open-angle glaucoma. Some studies have shown that perhaps half of people living with glaucoma aren't even aware they have the disease. Worldwide, an estimated 66.8 million people are visually impaired due to glaucoma, and an estimated 6.7 million are blind.

Glaucoma is a leading cause of blindness among African Americans and Hispanics in the U.S. Three times as many African Americans have glaucoma than Caucasians, and four times as many are blind. Between the ages of 45 and 64, glaucoma is fifteen times more likely to cause blindness in African Americans than in Caucasians. All people older than 60 are at a greater risk of developing glaucoma than people who are younger.

There are two main forms of glaucoma: open-angle (the most common form, affecting approximately 70-95% of individuals); and angle-closure. There are also several other forms of glaucoma, including normal-tension, congenital, juvenile, and secondary.

Open-angle glaucoma, the most common form of the disease, is progressive and characterized by optic nerve damage. The most significant risk factor for the development and advancement of this form is high eye pressure. Initially, there are usually no symptoms, but as eye pressure gradually builds, at some point the optic nerve is impaired and peripheral vision is lost. Without treatment, an individual can become totally blind.

Angle-closure glaucoma may be acute or chronic. In acute angle-closure glaucoma, the normal flow of eye fluid (aqueous humor) between the iris and the lens is suddenly blocked. Symptoms may include severe pain, nausea, vomiting, blurred vision, and seeing a rainbow halo around lights. Acute angle-closure glaucoma is a medical emergency and must be treated immediately, or blindness could result in one or two days. Chronic angle-closure glaucoma progresses more slowly and can damage the eye without symptoms, similar to open-angle glaucoma.

Normal-tension glaucoma occurs when eye pressure is normal, yet the optic nerve is damaged and peripheral vision is lost. Lowering eye pressure through medication sometimes slows the progress of the disease, but this type of glaucoma may worsen despite low pressure. The treatment is generally the same as for open-angle glaucoma.

Congenital glaucoma affects infants born with defects that prevent the normal drainage of fluid from the eye.

Juvenile glaucoma is open-angle glaucoma that affects children, adolescents and young adults.

Secondary glaucoma can be open-angle or closed-angle and is the result of some other medical condition in the eye or the body.

Marijuana derivatives taken orally, intravenously, or by smoking lower the eye pressure only briefly. The active ingredient does not cause reduction of eye pressure when administered in an eye drop formulation. The effects of marijuana are brief, lasting only hours, and are thus not suitable for long-term eye pressure control. Because marijuana can also reduce blood pressure briefly, it may be associated with reduced blood supply to the optic nerve, which could adversely affect patients with glaucoma. Thus, medical marijuana is not recommended in the treatment of glaucoma.

There are a great many resources available to people with low vision and their caretakers. For instance, every state has an agency on aging. You may find it in the phone book, online, or with the help of a librarian or friend.

Professional low vision therapists at eye clinics or other organizations can assist you. Let your eye doctor know what kind of limitations you are experiencing due to vision loss. He or she can then refer you to a vision rehabilitation center, where a low vision therapist can work with you to help you adapt and resolve specific problems.

You can also modify your environment, use low vision aids, develop your senses of hearing and touch, and practice using peripheral vision. Your doctor can prescribe optical devices such as magnifiers. Many non-prescription magnifying glasses and devices are also available to assist with reading and other close work, such as sewing or model-building. These devices range from the simple and inexpensive to more expensive high-tech products that can aid in using computers and watching television.

Many styles of magnifiers, including discreet ones, can be found at drug stores, medical supply stores, or may be ordered online or by phone through low vision product catalogs. A hand-held magnifying glass can help with reading medicine bottle labels, mail, price tags in stores, and restaurant menus. Other magnifiers come in the form of eyeglasses or clip onto glasses to free your hands for other activities.

Commonly used household items with large numbers and letters, and others that "talk," are also available. There are many sources for large-print books and audio materials, as well as services that read newspapers and magazines by phone or over the radio.

Electronic reading aids are proliferating, such as: computer programs that magnify the computer screen and/or read screen text out loud; special scanners to carry while shopping that read out prices, sizes, and colors; web browser plug-ins; and smartphone applications. One specialized device can take pictures of signs or menus and read the words in the pictures aloud.