Adult Glaucoma Suspect

Glaucoma is usually high pressure inside the eye that damages the optic nerve and can result in permanent vision loss. Not all 3 criteria (that is, high pressure inside the eye, optic nerve damage, and vision loss) are required to diagnose glaucoma; however, a diagnosis of glaucoma is certain when all 3 criteria are present.

Elevated pressure inside the eye, called intraocular pressure (IOP), is a primary concern because it is one of the main risk factors for glaucoma. In fact, the prevalence of primary open-angle glaucoma (POAG), the most common form of glaucoma, is higher with increasing IOP.

Eye pressure is measured in millimeters of mercury (mm Hg). Normal eye pressure ranges from 10-21 mm Hg. Elevated IOP is a pressure of greater than 21 mm Hg. The term ocular hypertension (OHT) refers to any situation in which IOP is higher than normal.

Glaucoma suspect describes a person with one or more risk factors that may lead to glaucoma, including increasing IOP, but this person does not yet have definite optic nerve damage or vision loss due to glaucoma.

A great overlap can exist between findings in people with early glaucoma and in those who are glaucoma suspect and without the disease.

Because of this, regular eye examinations with an ophthalmologist (a medical doctor who specializes in eye care and surgery) are very important to identify and treat people who are glaucoma suspect. By monitoring them for the earliest signs of glaucomatous damage, visual function can often be preserved.

In individuals who are at a high risk of developing glaucomatous damage, preventive measures, including lowering the pressure inside the eye, may be needed.

In the United States, glaucoma is the second most common cause of legal blindness.

• Between 80,000-116,000 persons are legally blind because of glaucoma. Each year, an additional 5,500 people are estimated to become legally blind.
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• At least 2.25 million people older than 40 years have glaucoma, but only half of them are aware of it and are being treated.
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• Elevated IOP is estimated to affect 5-10 million Americans, placing them at risk for glaucomatous damage. Each year, about 1% of individuals with OHT develop glaucomatous damage. In addition, one tenth of people with OHT lose vision within 10 years.
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• More than 7 million office visits occur per year to monitor people with glaucoma or to observe those who are glaucoma suspect.
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• In the United States in 1977, $400 million was spent on direct health costs related to glaucoma; $1.3 billion was lost because of decreased productivity.

Worldwide, more than 100 million people have elevated IOP.

• More than 3 million people worldwide are blind because of POAG.
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• About 2.4 million people develop POAG each year.

Race can be a factor in the development of glaucoma.

• Glaucoma is the leading cause of blindness in African Americans. African Americans have a significantly increased risk for developing POAG. The prevalence of POAG is 3-6 times higher in African Americans than in whites; glaucoma also usually occurs earlier. African Americans who are diagnosed with glaucoma not only are 4-8 times more likely to become blind but also go blind 8 times faster.
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• Asians, Canadians, Alaskans, Greenland Inuit Indians, and certain South American Indians are at an increased risk for narrow-angle glaucoma.

POAG affects men and women equally, although women are at a greater risk for angle-closure glaucoma than men. 

Increasing age is a definite risk factor.

• The risk of POAG increases with advancing age.
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• The prevalence of POAG is 3-10 times higher among individuals older than 80 years than among people in their 40s.

The mechanisms that cause glaucoma are not fully understood. In most cases, a painless elevation of IOP occurs, which can lead to progressive vision loss and optic nerve damage.

High pressure inside the eye is caused by an imbalance in the production and drainage of fluid in the eye (called aqueous humor). The channels (called trabecular meshwork) that normally drain the fluid from inside the eye do not function properly. More fluid is continually being produced but cannot be drained because of the improperly functioning drainage channels. This results in an increased amount of fluid inside the eye, thus raising the pressure.

Another way to think of high pressure inside the eye is to imagine a water balloon. The more water that is put into the balloon, the higher the pressure inside the balloon. The same situation exists with too much fluid inside the eye—the more fluid, the higher the pressure. Also, just like a water balloon can burst if too much water is put into it, the optic nerve in the eye can be damaged by too high of a pressure. See Media files 1-2.

Certain risk factors are associated with the development of glaucomatous damage. The greater the number and the degree of risk factors, the greater the risk of developing glaucoma over time.

The following historical and demographic factors have shown a high association for the disease:

• Family history is a definite risk factor.
  
  
  • Between 10-20% of people with glaucoma have a positive family history.
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  • Family history of glaucoma in a sibling is the greatest risk factor, followed by glaucoma in a parent. One survey found that the risk of having glaucoma is increased 3.7-fold for individuals who have siblings with POAG.
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• Increasing age
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• Race, particularly African American

In addition to elevated IOP, the following eye conditions have been implicated as risk factors for developing glaucoma:

• Glaucoma already present in one eye
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• Congenital abnormalities (abnormalities present from birth): The underlying cause of glaucoma may be from congenital variations in the eye, especially in the appearance of the optic nerve.
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• Onetime trauma to the eye or prior eye surgery: This may indicate that the optic nerve damage is not progressive but may have been because of an isolated incident. The key is whether any progression occurs.
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• Suspicious looking optic nerve or an optic nerve defect
  
  
  • Susceptibility of the optic nerve to damage varies from individual to individual. Along with other risk factors, the likelihood of optic nerve damage also depends on the level of IOP.
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  • Problems with blood supply to the optic nerve may play a role. This is especially important in individuals with normal-tension glaucoma who have progressive disease despite IOP of less than 21 mm Hg. See Normal-Tension Glaucoma.
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• Narrow angles
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• Nearsightedness (myopia)
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• Pseudoexfoliation: Flakes of material are produced inside the eye that obstruct the trabecular meshwork, causing a rise in IOP.
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• Pigment dispersion
  
  
  • The iris releases pigment inside the eye that obstructs the trabecular meshwork, causing a rise in IOP.
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  • With pigment dispersion, the risk of glaucoma increases by 25-50%.
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• History of uveitis or other inflammatory eye disease: Uveitis is an inflammation of the uvea, that is, the iris, the ciliary body, and the choroid.
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• Central retinal vein occlusion: Some people’s first sign of disease from elevated IOP can be sudden vision loss due to the vein in the central part of the retina becoming blocked, called a central retinal vein occlusion.

The following medical conditions have been associated as risk factors for developing glaucoma:

• Current or past use of topical steroids
  
  
  • Topical steroids may elevate IOP in certain people.
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  • Optic nerve damage may occur from a previous episode of increased IOP associated with topical steroid use. The elevation of IOP is usually seen within a few weeks of starting topical steroids.
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• Diabetes
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• History of vasospastic disorders (spasms or constrictions of the blood vessels): Migraine headaches occur more often in people with normal-tension glaucoma.
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• Heart disease, particularly in those with normal-tension glaucoma

People who are glaucoma suspect do not usually experience any symptoms. Those with possible angle-closure glaucoma may experience intermittent headaches, see haloes, or have blurred vision. By the time people with glaucoma would notice vision loss, significant amounts of optic nerve damage and vision loss have already occurred. The optic nerve damage and vision loss are permanent.

Because of the lack of symptoms associated with glaucoma, regular eye examinations with an ophthalmologist are extremely important if you are glaucoma suspect and at high risk.

If glaucoma is already present in one eye, the other eye is at an increased risk of future damage. In about 29% of untreated undamaged fellow eyes, vision loss occurs in an average of 5 years.

|Questions to Ask the Doctor|

• Is my eye pressure elevated?
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• Are there any signs of internal eye damage due to an injury?
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• Are there any optic nerve abnormalities on my examination?
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• Is my peripheral vision normal?
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• Is treatment necessary?
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• How often should I undergo follow-up examinations?

IOP is an important risk factor for developing glaucomatous damage, but, alone, it is not sufficient for a diagnosis of glaucoma.

Some eyes undergo damage at IOP of less than 18 mm Hg, while others tolerate IOP of more than 30 mm Hg. In fact, as many as 50% of people with optic nerve damage or visual field changes due to glaucoma have IOP of less than 21 mm Hg on their initial evaluation.

During an eye examination, your ophthalmologist performs tests to measure IOP as well as to rule out early POAG or other possible causes of glaucoma. These tests are explained below.

• Tonometry is a method used to measure the pressure inside the eye.
  
  
  • Measurements are taken for both eyes on at least 2-3 occasions. Because IOP varies from hour to hour in any individual, measurements may be taken at different times of day (eg, morning and night). If you are a glaucoma suspect with normal IOP but a suspicious looking optic nerve, your IOP may be checked several times during a single day (called a diurnal assessment or diurnal curve).
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  • A difference in pressure between each eye of 3 mm Hg or more may suggest glaucoma. Early POAG is very likely if IOP is steadily increasing.
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  • In general and depending on your risk factors, IOP is checked every 3-12 months.
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• The front of your eyes, including your cornea, anterior chamber, iris, and lens, are examined using a special microscope called a slit lamp. During a slit lamp examination, the ophthalmologist looks for signs of other causes or risk factors of glaucoma.
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• Gonioscopy is performed to check the drainage angle of your eye; to do so, a special contact lens is placed on the eye.
  
  
  • This test is important to evaluate angle depth and to determine if the angles are open, narrowed, or closed. Narrow or closed angles reduce or stop the fluid flow from the eye, causing increased pressure.
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  • Gonioscopy is also used to rule out any other conditions that could elevate IOP.
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  • Gonioscopy is usually performed annually on all people who are glaucoma suspect.
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• Each optic nerve is examined for any damage or abnormalities; this may require dilation of the pupils to ensure an adequate examination of the optic nerves.
  
  
  • Different imaging studies may be conducted to document the status of your optic nerve and to detect changes over time.
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  • Fundus photographs, which are pictures of your optic disc (the front surface of your optic nerve), are taken for future reference and comparison in order to monitor any possible subtle progression.
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  • In certain people, ophthalmologists prefer to obtain this documentation yearly for detailed comparison.
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• The retina is examined for any defects. This may also require dilation of the pupils to ensure an adequate examination of the retina.
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• Visual field testing checks your peripheral (or side) vision, typically by using an automated visual field machine.
  
  
  • This test is done to rule out any visual field defects due to glaucoma. However, an absence of visual field defects does not ensure the absence of glaucoma. Visual field defects may not be apparent until as much as 50% of the optic nerve fiber layer has been lost.
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  • Visual field examinations are typically done every 6-12 months. If there is a low risk of glaucomatous damage, then the test may be performed only once a year. If there is a high risk of glaucomatous damage, then the test may be performed as frequently as every 2 months. Testing is repeated sooner if a defect is detected, usually within 1 month, to ensure that the defect is reproducible.

|Self-Care at Home|

If your ophthalmologist prescribes a medicine to help in lowering the pressure inside your eye, complying with your eye doctor’s instructions and properly applying the medication are very important (see How to Instill Your Eyedrops). Not doing so could result in an additional increase in IOP that can further affect the optic nerve and cause permanent vision loss.

|Medical Treatment|

The decision to treat a person who is glaucoma suspect and at high risk is highly individualized. You may be treated with medications or just observed. Your ophthalmologist will discuss the pros and cons of medical treatment versus observation with you.

• Even with such risk factors as a suspicious looking optic nerve, an optic nerve defect, or a family history of glaucoma, you may only be observed.
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• Your situation and risk factors are carefully evaluated to determine the likelihood of glaucomatous damage and to evaluate the necessity and effectiveness of medical treatment.
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• In general, most ophthalmologists medically treat those with IOP of greater than 30 mm Hg because of the high risk of optic nerve damage.

If you are glaucoma suspect and at high risk, your ophthalmologist may decide to treat you with one or more medicated eyedrops, which have been shown to be beneficial in lowering IOP. By using a pressure-lowering medication, subsequent damage due to glaucoma may be delayed or even prevented. See Medications.

In determining an appropriate medicine, your ophthalmologist considers the drug’s adverse effects and frequency of use, along with your ocular and medical histories. Animal data suggest that the glaucoma medicines Alphagan, Xalatan, and Betoptic may play a role in improving the blood supply to the optic nerve.

If, upon examination, progression to glaucoma is seen along with optic nerve damage and/or reproducible visual field defects, your ophthalmologist will start medical treatment immediately, which would include medicated eyedrops and possibly surgery.

|Medications|

See Understanding Glaucoma Medications.

|Surgery|

If the anterior chamber angle depth is very shallow, laser peripheral iridotomy may be recommended as a preventive measure. During a laser iridotomy, the ophthalmologist uses a laser to make a hole in the iris (the colored part of the eye) to decrease the risk of acute angle-closure glaucoma.

Conventional incisional surgery (known as filtering procedures) is generally reserved for people with documented optic nerve damage due to glaucoma. The most common filtering surgery is trabeculectomy.

During trabeculectomy, the ophthalmologist creates an alternate pathway (or drainage channel) in the eye to increase the passage of fluid from the eye. By constructing a new drainage channel, the fluid is able to flow better outside the eye. As a result, IOP is lowered.

Laser trabeculoplasty is infrequently needed for treating people who are glaucoma suspect. During this procedure, the ophthalmologist uses an argon laser beam to place small spots (burns) on the trabecular meshwork, which further open the holes in the trabecular meshwork, allowing the fluid (aqueous humor) to flow better out of the eye.

|Follow-up|

Because glaucoma causes silent damage, continuous follow-up care is essential to monitor any progressive change over time that may warrant treatment. The frequency of your follow-up visits also depends on the following:

• Age
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• Level of IOP elevation
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• Optic nerve appearance
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• Family history of glaucoma
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• Presence of additional risk factors
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• Any progression of disease

|Prevention|

A person cannot avoid becoming a glaucoma suspect, but through regular eye examinations with an ophthalmologist, any progression to glaucoma can hopefully be prevented.

|Outlook|

Most people who are glaucoma suspect do not develop optic nerve damage and/or vision loss.

Overall, about 1% of individuals with OHT develop glaucoma per year. The risk is higher for people who have additional risk factors besides elevated IOP.

Without treatment, optic nerve damage may progress, resulting in a progressive loss of peripheral (or side) vision. Irreversible blindness may eventually occur.

|Support Groups and Counseling|

Glaucoma can cause silent damage with eventual vision loss. People who are glaucoma suspect should be educated about their risk factors, their prognosis, and the importance of follow-up care.

American Academy of Ophthalmology
655 Beach Street
Box 7424
San Francisco, CA 94120
(415) 561-8500
 
Glaucoma Research Foundation
490 Post Street, Suite 1427
San Francisco, CA 94102
(800) 826-6693
 
Prevent Blindness America
500 East Remington Road
Schaumburg, IL 60173
(800) 331-2020
 
The Glaucoma Foundation
116 John Street, Suite 1605
New York, NY 10038
(212) 285-0080 

Lighthouse International
111 East 59^th Street
New York, NY 10022-1202
(212) 821-9200
(800) 829-0500

|Web Links|

American Academy of Ophthalmology

Glaucoma Research Foundation

Prevent Blindness America

The Glaucoma Foundation

Lighthouse International

Media file 1: Parts of the eye. Although the eye is small, only about 1 inch in diameter, each part plays an important role in your ability to see the world around you.

Media type:  Illustration

Media file 2: Intraocular pressure. Elevated eye pressure is caused by a build-up of fluid inside the eye because the drainage channels (trabecular meshwork) cannot drain it properly. Elevated eye pressure can cause optic nerve damage and vision loss.

Media type:  Illustration

ocular hypertension, OHT, ocular hypertensives, high pressure inside the eye, intraocular pressure, IOP, increased IOP, elevated IOP, high IOP, increased intraocular pressure, elevated intraocular pressure, high intraocular pressure, high eye pressure, elevated eye pressure, increased eye pressure, optic nerve, optic nerve damage, visual field defect, peripheral vision, side vision, vision loss, blindness, adult glaucoma suspect

Author: U Fusun Cardakli, MD, Consulting Staff, Altoona Ophthalmology Associates.

Coauthor(s): Lauri Graham, Medical Writer, .com, Inc.

Editors: Richard W Allinson, MD, Associate Professor, Division of Ophthalmology, Texas A&M University Health Science Center, Associate Professor, Department of Surgery, Scott and White Clinic; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, ; Robert H Graham, MD, Ophthalmologist, Robert H Graham, MD, PC; Affiliated With Department of Ophthalmology, Mayo Clinic, Scottsdale, Arizona and Carl T Hayden VA Medical Center, Phoenix, Arizona.