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Keep Things In Focus With Regular Eye Exams

How often should you get tested?

The American Academy of Ophthalmology recommends the following schedule for eye exams:

Under 40: an initial comprehensive exam should be enough, unless you experience vision problems or injury. However, you should get an exam every three to five years if you're African American because of the high risk for glaucoma, or if you have a family or personal history of eye disease.
Ages 40 to 64: every two to four years, even if you have no symptoms.
Ages 65 and older: every one to two years, even if you have no symptoms.

Why you should get tested?

There are a number of ocular problems -- including cataracts, glaucoma, macular degeneration, and diabetic retinopathy -- that develop over time and that make periodic eye exams extremely important.

What to expect

Be prepared to answer questions about your medical history, including allergies, medications, past eye diseases and surgeries. It will also be useful for your doctor to know about your family's medical history. If you have glasses -- even if you don't always wear them -- bring them to your exam.

Your ophthalmologist's understanding of your medical history and test results is the key to revealing any vision or ocular-related problems.

Exactly which tests will be included in your eye examination depend on a number of factors, including your age, medical history, and date of your last exam. What follows are descriptions of each.

Visual acuity tests

These tests measure how well you can see images from a distance and up close. To test distance vision, you will stand in a dimly lit room at a specified distance -- usually 20 feet -- from a chart with letters that get progressively smaller. First covering one eye, then repeating with the other, you will read the smallest line you can. If you wear glasses, this same test can be done to assess their strength.

Your distance vision is determined using two numbers, with 20/20 vision being normal. The first represents the distance from the chart when you were tested. The second is the distance at which someone with normal vision would be able to see the smallest line you were able to read. So as the second number increases, the less powerful your distance vision: A score of 20/25 means your vision is poorer than normal because you need to be five feet closer to the smallest line in order to see it.

Near vision is tested in a well-lit room by having you read from a card with various print sizes at your normal reading distance. This test is also done one eye at a time, and if you wear glasses, first without them and then with them.

Near vision is calculated in the same way as distance, but with 14/14 being normal because most people hold the card 14 inches away when they read. Once again, the higher the second number, the worse your vision.

Normal test results are not a guarantee of normal vision. Some vision problems may not be apparent from these tests and further ones may be needed. If your results are less than normal, more testing will be necessary.

Determining refractive error

If objects do not focus correctly, that usually means you have a refractive error. These include: nearsightedness (myopia, or inability to see distant objects clearly), farsightedness (hyperopia, or problems seeing close images clearly), distorted vision (astigmatism), problems changing focus from distant to near (presbyopia).

In such cases, corrective lenses can improve vision. A phoropter, a machine that has trial lenses that can be put into place, can be used to find the correct prescription for you.

Eyelid and eye muscles examination

Changes in the eyelids, tear glands, drainage system, and areas around the eye often accompany thyroid disease, stroke, and tumors in the brain or eye sockets, so visual inspection of these areas is important.

Watching how your eyes move can tip your doctor off to misalignments and coordination and neurological problems. Movement is controlled by your eye muscles, which can be evaluated by how the eye muscles respond to bright light. If your response is abnormal, it can be a sign of ocular or neurologic problems.

Tonometry test

Eye pressure is determined using a tonometer, a device that is put near your eyes, sometimes even touching them. Because your cornea is sensitive, anesthetic drops may be given to numb your eyes beforehand. (These drops can cause your near vision to be blurry for a couple hours and may make your eyes sensitive to light. If you have glaucoma or have had a bad reaction to drops before, be sure to tell your doctor.) Eye pressure should be between 7 and 22 millimeters of mercury. If it's too high, it can be a sign of glaucoma, while pressure that is too low can bring about other eye problems.

Slit lamp examination

The front of the eye is examined using a slit lamp, a lighted instrument with a binocular microscope that can have a special camera attached. The slit lamp is focused into the eye so the doctor can look at the lids, lashes, irises, and lenses. The exam takes five to ten minutes and doesn't hurt, but you need to stay still while it's done. You will need to take out contact lenses unless the test is being done to test their fit.

Your doctor may give you eye drops for the exam, which can cause your near vision to be blurry for a couple hours and may make your eyes sensitive to light. (If you have glaucoma or have had a bad reaction to drops before, be sure to tell your doctor.)

Ophthalmoscope exam

This test allows the doctor to look at the retina, or back of your eye, using an ophthalmoscope, a small device that shines a bright light into your eye. This exam usually takes no more than five minutes and you may be given drops to dilate your pupils. (This can make your vision blurry for a couple hours and may make your eyes sensitive to light. Let your doctor know if you are allergic to eye drops or have glaucoma, because the drops should not be used in such cases.)

This procedure, as well as your doctor's interpretation of it, is a key part of your comprehensive exam. It can reveal a number of eye problems, including a detached retina, cataracts, and glaucoma, as well as detect the effects of diabetes, high blood pressure, and other diseases that affect the eye.

Visual field test

Testing of your visual field, which is everything you see straight ahead and to the side, is done to detect diseases such as glaucoma, as well as brain and eye tumors. It can also help determine the cause of headaches.

A patch is put first over one eye, and then over the other, so each can be tested individually, since many conditions affect only one eye. You will look straight ahead and watch for a target to appear. It's important not to move your eyes to find the target, but wait until it comes into your line of view so your side vision is tested as well. Your doctor will give you specific instructions about how to respond during the test. If it's difficult or tiring, it probably means the computer is making the test harder because your eyesight is better than normal.