What’s in an Eye Test?

It's important for adults to have eye exams on a regular basis to check for problems. Regular eye exams are critical for detecting:

  • Glaucoma
  • Macular Degeneration
  • Cataracts
  • Diabetic retinopathy
  • Changing Vision

But everyone needs regular eye exams.  This is particularly important if you have risk factors or a family history of eye problems. Children need their vision checked at 6 months, 3 years, and before first grade.

Adults should see an optometrist at least every two years and annually after age 60.

Your optometrist may recommend more frequent exams if you have a health condition such as diabetes or glaucoma, macular degeneration, work in a visually demanding job, or take medications that can affect eyesight.

Preparing for Your Eye Exam

When you call to make an appointment for an eye exam, briefly and clearly describe any vision problem you're having. Before you go, list questions for the eye optometrist. Be prepared to discuss any medication you're taking and your (and your family's) eye health history. 

When you go, take your glasses and/or contact lenses, if you use them, and sunglasses for the trip home with your pupils dilated.

During Your Eye Exam

Your eye exam may take from half an hour to an hour. It will evaluate both your vision and the health of your eyes. At the beginning the optometrist will take your medical and vision history. You'll likely have all or most of the following eye tests (you may also have more specialized eye tests):

Eye muscle movement test: To test muscle strength and control, the optometrist will ask you to visually track a target in different directions and observe your eye movements.

Cover test: This is a check for how well your eyes work together. As you stare at a small target some distance away, the optometrist will cover and uncover each eye to observe how much your eyes move, watching for an eye that turns away from the target (strabismus or "lazy eyes"). The test may be repeated with a target close to you.

External exam and pupillary reactions: The optometrist will watch the reactions of your pupils to light and objects at close distance. At the same time, the doctor will check the exterior eye, looking at things such as the condition of the white of the eyes and the position of your eyelids.

Visual acuity test: You'll sit in front of an eye chart, with letters that get smaller as you read down each line. You cover each eye in turn and, using the other eye, read aloud, going down the chart, until you can't read the letters anymore.

Retinoscopy: The optometrist may shine a light in your eyes and flip lenses in a machine (phoropter) that you look through while staring at a chart or use an automated machine (refractor) for the same purpose. By checking the way light reflects from your eyes, the optometrist gets an approximate idea of the lens prescription you need now.

Refraction testing: For your exact lens prescription, the optometrist may use the results of the computerized refractor, or he or she may fine-tune the prescription manually by asking you to respond to questions such as,
"Which is better, first or second?" while flipping back and forth between different lenses. If you don't need corrective lenses, you may not even have this test.

Slit lamp (biomicroscope): The slit lamp magnifies and lights up the front of your eye. The optometrist uses it to detect several eye diseases and disorders by examining your cornea, iris, lens, and anterior chamber.

Retinal examination: Using an ophthalmoscope and sometimes pupil dilation, the optometrist examines the back of your eyes: retina, retinal blood vessels, vitreous, and optic nerve head.

Glaucoma testing: This tests whether the fluid pressure inside your eyes is within a normal range. Painless and taking just a few seconds, the test can be done several ways.

  • The tonometer test: This is the most accurate. With drops numbing your eyes, you stare directly ahead. The optometrist barely touches the front surface of each eye with an instrument called an applanation tonometer or Tonopen to measure the pressure.
  • The "puff of air" or non-contact tonometer test: While you focus on a target, you get a small "puff" of air in each eye. Resistance to the air puff indicates the pressure.

Pupil dilation (enlargement): With your pupils fully enlarged, the optometrist will examine the inside of your eyes with different instruments and lights or take an image using a special camera.  The pupil-enlarging drops for this part of your eye exam start to work after about 15-20 minutes, making your eyes more sensitive to light and blurring your vision.

These effects may last for several hours or longer so it's important to bring a pair of sunglasses to your exam for the ride home. This test is common for people who suffer with diabetes or macular degeneration.

Visual field test (perimetry): Your visual field is the area you can see in front of you without moving your eyes. Using one of three tests, the optometrist "maps" what you see at the edges (periphery) of your visual field, using this map in diagnosing your eye condition.

If you have normal healthy vision the optometrist will recommend a review of your vision in about 2 years time. This may be sooner if he or she wishes to follow up on any potential or ongoing eye disease or problems you may have.