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Glaucoma: Tests & Diagnosis

by MariAnne

Glaucoma most often occurs in adults over age 40, but it can also occur in young adults, children, and infants. In African Americans, glaucoma occurs at an earlier age and with greater incidence of vision loss. Each person over 40 of age, with family history of glaucoma, poor vision, diabetes and usage of corticosteroid medications, such as prednisone has higher risk for developing glaucoma. That is why many people wish to learn more about tests and diagnosis of this serious condition.

Diagnosis of glaucoma

A diagnosis of glaucoma no longer simply relies on the presence of pressure within the eye as it used to be before. It requires that there be optic nerve damage or a strong suggestion of damage. The doctor is able to see it clearly during a dilated eye examination of the optic nerve. In general, the hallmark sign of this condition is a loss of peripheral vision, where a person can see in front of him or herself but has lost the vision to the side. Many people keeps wondering why does pressure rise in the eye to cause glaucoma. The reason is that g laucoma usually occurs when intraocular pressure increases. This occur when the fluid pressure in the eye’s anterior chamber, the area between the cornea and the iris, raise more then normal. This fluid, called aqueous humor, flows out of the eye through one channel. If this channel becomes blocked, fluid builds up causing glaucoma although the direct cause of this blockage is unknown. However, doctors do know that it commonly inherited, meaning it passes from parents to children. Less common causes of glaucoma include a blunt or chemical injury to the eye, severe eye infection, blockage of blood vessels in the eye, inflammatory conditions of the eye, and eye surgery to correct another condition. Glaucoma usually occurs in both eyes, but it may also involve each eye to a different extent. An ophthalmologist will test your vision and examine your eyes through dilated pupils, but the doctor will also perform a procedure called tonometry to check for eye pressure.

Glaucoma tests are painless and take very little time so you should not be worried.

What are the types of glaucoma?

There are two main types of glaucoma.

Open-angle glaucoma or wide-angle glaucoma is the first one. This is the most common type of glaucoma. The structures of the eye appear normal, but fluid in the eye does not flow properly through the drain of the eye. This is famous as the trabecular meshwork.
Angle-closure glaucoma or acute or chronic closed-angle or narrow-angle glaucoma is second. This type of glaucoma is less common, but can cause a sudden buildup of pressure in the eye with poor drainage. This is because the angle between the iris and the cornea, where a drainage channel for the eye is located, is too narrow. On the other hand, the pupil could open too wide, narrowing the angle and blocking the flow of the fluid through that channel.

What are the symptoms of glaucoma?

For most people, there are usually few or no symptoms of glaucoma, but the first sign of glaucoma is often the loss of peripheral or side vision. This symptom can go unnoticed until late in the disease. Detecting glaucoma early is one reason you should have a complete exam with an eye specialist every one to two years because intraocular pressure can rise to severe levels. In these cases, sudden eye pain, headache, blurred vision, or the appearance of halos around lights may occur as the main symptoms. If you have any of these symptoms, seek immediate medical care. You should especially watch symptoms such as seeing halos around lights, narrowing of vision, vision loss, and redness in the eye, or eye that looks hazy. If you experience nausea, vomiting, or pain in the eye you should also see the doctor.

How to treat glaucoma

Glaucoma treatment may include prescription eye drops, laser, or even microsurgery.

Eye drops for glaucoma either reduce the formation of fluid in the front of the eye or increase its outflow. Side effects of glaucoma drops may include allergy, redness of the eyes, brief stinging or visual blurring. You could also experience irritated eyes. Some glaucoma medications may affect the heart and lungs so you must be sure to tell your doctor about any glaucoma medication you are currently taking or are allergic to.
Laser surgery for glaucoma slightly increases the outflow of the fluid from the eye in open-angle glaucoma. It could also eliminate fluid blockage in angle-closure glaucoma. Types of laser surgery for glaucoma include trabeculoplasty, in which a laser pulls open the trabecular-meshwork drainage area. Another method is iridotomy, in which a tiny hole in the iris allows the fluid to flow more freely. Your doctor could also choose cyclophotocoagulation, in which a laser beam treats areas of the ciliary body, reducing the production of fluid.
Microsurgery for glaucoma is procedure where a new channel creates to drain the fluid, thereby reducing intraocular pressure that causes glaucoma. Sometimes this form of glaucoma surgery fails and the doctor must repeat it. Other complications of microsurgery for glaucoma are some temporary or permanent loss of vision, as well as bleeding or infection.
The best treatment for open-angle glaucoma is various combinations of eye drops, laser trabeculoplasty, and microsurgery. Traditionally in the U.S., medications are the first choice, but there is increasing evidence that some people with glaucoma may respond better with early laser surgery or microsurgery. However, you should talk to your doctor to find out which glaucoma treatment is right for you. Although, you cannot prevent glaucoma but if your doctor diagnose and treat you early, he could control the disease.

Tests for glaucoma

Ophthalmologists use three types of tests to screen for glaucoma in people at risk to make the diagnosis. These tests also help to follow people during treatment. The three tests are tonometry to measure intraocular pressure, ophthalmoscopy to inspect the optic nerve, and perimetry to test the visual fields. A high IOP warrants further testing, and the final diagnosis is made by also finding evidence of optic nerve damage. The doctor could also diagnose you by identifying defects in the visual fields characteristic of glaucoma.

Tonometry measures intraocular pressure or IOP, by assessing the amount of force necessary to make a slight indentation in a small area of the cornea. The most effective way to do this is with applanation tonometry, where anesthetic eye-drops are going into numb the eye. Then, doctor will need a slight pressure to the cornea with a small instrument while he looks through a table-mounted microscope. A handheld tonometry device also is sometimes used and is relatively accurate. Tonometry is painless and poses virtually no risk to the cornea during this test.
Ophthalmoscopy is specific examination of the optic nerve, required for the diagnosis of glaucoma. It also helps with periodic examinations of the nerve valuable to follow the progress of the disorder during treatment. To perform ophthalmoscopy, the doctor dilates pupils with eye-drops and then uses an ophthalmoscope. This is a special instrument with a small light on the end--to magnify and examine the optic nerve. Another type of ophthalmoscopy uses a specialized microscope that allows three-dimensional visualization of your optic nerve. Signs of a damaged optic nerve include cupping in its center and a loss of its normal pink color.
Perimetry is procedure where the patient wears a patch over one eye and looks straight ahead at a bowl-shaped white area. In the same time, the computer presents lights in fixed locations around the bowl. The patient indicates each time he or she sees a light, which is why perimetry is able to provide a map of the visual fields. The type of vision loss associated with glaucoma is relatively specific, and perimetry can detect the typical visual-field defects of glaucoma disorder.

A thorough eye examination including gonioscopy with a Goldmann or Zeiss goniolens is a prerequisite prior to undergoing specific tests for glaucoma. In glaucoma management, serial tests over several years have more value than a single one-time test for diagnosis. Therefore, it is important that same type of test repeat many times over a period of several years. The reason why this is so is that we are trying to ascertain whether a given target pressure has indeed stopped further damage to the eye. This determination is only possible if we have examinations from previous years to compare against and it can show that there are no new findings or worsening. Therefore, one must maintain good long-term records and if you change physicians for any reason, it is important that you have all prior records forwarded to the current physician.

The newer tests for glaucoma

The visual field test depends upon patient responses. The new tests are nerve fiber analyzers, and these adopt a different objective strategy that is not dependent on patient responses. These tests measure the physical thickness of the nerve fibers in the retina. Since in glaucoma the nerve fibers are lost, patients with glaucoma are likely to have thinner nerve fiber layer. By measuring changes in nerve fiber layer thickness over time, these tests can detect glaucoma progression. The validity of these tests has been established in many peer-reviewed reports. Perhaps these tests will become the gold standards in the future as more experience gain with these tests and although they become more widely available, however at present they are best considered supplemental tests in glaucoma diagnosis. Going by the logic that more information is better than less a reasonable argument are easy to get from these tests in addition to the traditional tests, even if their role in glaucoma management is debatable.