Glaucoma causes no early symptoms
January is National Glaucoma Awareness Month
What is Glaucoma?
Everyone is at risk for glaucoma. However, certain groups are at higher risk than others. People at high risk for glaucoma should get a complete eye exam, including eye dilation, every year.
More than 2.2 million Americans age 40 and older suffer from glaucoma. Nearly half do not know they have the disease—it causes no early symptoms.
Glaucoma is a progressive disease of the eye that can lead to blindness if not treated. Glaucoma initially affects your peripheral vision, but will slowly work inward and affect your central vision if it becomes severe.
Glaucoma most often damages silently, with no pain or side effects. Basically it's a higher than normal fluid pressure inside of the eye that eventually damages the optic nerve and causes loss of peripheral vision.
Fortunately, treatment options do exist to reduce the progression of this disease, so a regular eye exam is very important. There are many prescription eye drops used to decrease the eye pressure and help reduce damage. Recent studies have now shown that many individuals can benefit from these eye drops as a preventative measure if they are found to have dangerously elevated pressures.
Early detection is the key to protecting your vision from damage caused by glaucoma. A complete eye exam includes five common tests to detect glaucoma.
It is important to have your eyes examined regularly.
High Risk Factors
Glaucoma is six to eight times more common in African Americans than in Caucasians.
You are six times more likely to get glaucoma if you are over 60 years old.
If members of your immediate family have glaucoma, you are at a much higher risk than the rest of the population. Family history increases risk of glaucoma four to nine times.
Recent studies indicate that the risk for Hispanic populations is greater than those of predominantly European ancestry, and that the risk increases among Hispanics over age 60.
People of Asian descent appear to be at increased risk for angle-closure glaucoma.Angle-closure glaucoma accounts for less than 10% of all diagnosed cases of glaucoma. People of Japanese descent are at higher risk for normal-tension glaucoma.
Steroid Use. Some evidence links steroid use to glaucoma. A 1997 study reported in the Journal of American Medical Association demonstrated a 40% increase in the incidence of ocular hypertension and open-angle glaucoma in adults who require approximately 14 to 35 puffs of steroid inhaler to control asthma. This is a very high dose, only required in cases of severe asthma.
Eye Injury. Blunt injuries that “bruise” the eye (called blunt trauma) or injuries that penetrate the eye can damage the eye’s drainage system, leading to traumatic glaucoma. The most common cause is sports-related injuries such as baseball or boxing.
Testing for Glaucoma
Regular eye examinations include two routine eye tests: tonometry and ophthalmoscopy.
Tonometry measures the pressure within your eye. During tonometry, eye drops are used to numb the eye. Then a doctor or technician uses a device called a tonometer to measure the inner pressure of the eye. A small amount of pressure is applied to the eye by a tiny device to establish internal fluid pressure.
Most glaucoma cases are diagnosed with pressure exceeding 20mm Hg. However, some people can have glaucoma at pressures between 12 -22 mm Hg. Eye pressure is unique to each person.
Ophthalmoscopy is a diagnostic procedure that helps the doctor examine your optic nerve for glaucoma damage. Eye drops are used to dilate the pupil so that the doctor can see through your eye to examine the shape and color of the optic nerve.
The doctor will then use a small device with a light on the end to light and magnify the optic nerve. If your intraocular pressure is not within the normal range or if the optic nerve looks unusual, your doctor may ask you to have one or two more glaucoma tests: perimetry and gonioscopy.
Perimetry is a visual field test that produces a map of your complete field of vision. This test will help a doctor determine whether your vision has been affected by glaucoma. During this test, you will be asked to look straight ahead and then indicate when you see a blinking light in your peripheral (or side) vision. This helps draw a "map" of your vision.
Do not be concerned if there is a delay in seeing the light as it moves in or around your blind spot. This is perfectly normal and does not necessarily mean that your field of vision is damaged. Try to relax and respond as accurately as possible during the test.
Your doctor may want you to repeat the test to see if the results are the same the next time you take it. After glaucoma has been diagnosed, visual field tests are usually done one to two times a year to check for any changes in your vision.
This diagnostic test helps determine whether the angle where the iris meets the cornea is open and wide or narrow and closed. During the exam, eye drops are used to numb the eye. A hand-held contact lens is gently placed on the eye. This contact lens has a mirror that shows the doctor if the angle between the iris and cornea is closed and blocked (a possible sign of angle-closure or acute glaucoma) or wide and open (a possible sign of open-angle, chronic glaucoma).
Pachymetry is a simple, painless test to measure the thickness of your cornea -- the clear window at the front of the eye. A probe called a pachymeter is gently placed on the front of the eye (the cornea) to measure its thickness. Pachymetry can help your diagnosis, because corneal thickness has the potential to influence eye pressure readings. With this measurement, your doctor can better understand your pressure reading and develop a treatment plan that is right for you. The procedure takes only about a minute to measure both eyes.
Optical Coherence Tomography (OCT)
The OCT is a non-invasive test that looks at the thickness of the tissue of the optic nerve. If this tissue is too thin, this can mean that the intraocular pressure is damaging the tissue which in turn can damage your peripheral visual field. This is important in the diagnosis of glaucoma. The OCT can also be done yearly to watch the thickness of the tissue and determine if the treatment for glaucoma is working. Glaucoma that is stable means the thickness of the optic nerve tissue stays stable and does not decrease.
Why Are There So Many Diagnostic Exams?
Diagnosing glaucoma is not always easy, and careful evaluation of the optic nerve continues to be essential to diagnosis and treatment. The most important concern is protecting your sight. Doctors look at many factors before making decisions about your treatment. If your condition is particularly difficult to diagnose or treat, you may be referred to a glaucoma specialist. A second opinion is always wise if you or your doctor become concerned about your diagnosis or your progress.