Eye Exam

In a routine eye exam, a person’s eyes are examined with special instruments that can detect normal and abnormal structures and conditions. The person’s visual acuity, peripheral vision and color vision, are measured, as well.

Who is a candidate for the test?

Everyone should have regular eye examinations. If a person does not have eye problems, it is recommended they have their eyes examined every 3 to 5 years until about the age of 50. After 50 years old, the eyes may need to be checked more frequently for eye disorders. If a person has other eye problems, the healthcare provider may recommend eye exams more frequently. Children should have their first eye exam at around the age of 3 or 4 years old.

How is the test performed?

First, the healthcare provider will ask about the eyes, any vision problems and general health. Next, he or she will test the eye muscles to see if eye movements are normal. Peripheral vision, or the ability to see out of the side of the eyes, can be tested as well. Often, the healthcare provider will put special eye drops into the eyes that cause the pupils to open wider, or dilate. When the pupils are wide open, the doctor can get a better view of the inside of the eyes.

Once the pupils are dilated, the healthcare provider will look into each eye with a special instrument called an ophthalmoscope. Through this instrument, the internal structures of the eye can be seen. These structures include the retina, the back of the eyeball or the fundus, the blood vessels and the head of the optic nerve, which carries the images a person sees to the brain. The surface of the cornea, the outermost portion of the front of the eye, can be examined for defects or scratches. The pressure inside the eyeball can be measured to test for glaucoma. Glaucoma is a disease of the eye in which there is increased pressure inside the eyeball. It can cause a gradual loss of vision.

After the eyeballs have been examined, the person is then asked to read a standard eye chart to determine how well the person can see, or to check the visual acuity. The person is usually assigned a numeric value for each eye, such as 20/20 vision or excellent vision, or 20/40 for poorer vision. The larger the bottom number of the fraction is, the worse the vision. Then, the person is given a series of colored dot patterns to test the ability to see colors.

What is involved in preparation for the test?

A person should request specific instructions from the healthcare provider. Usually, no preparation is necessary for a routine eye exam.

What do the test results mean?

Normal results include the following:

20/20 vision

the ability to see colors

normal optic nerve, retina, blood vessels, and fundus

no evidence of glaucoma

a transparent cornea free of scratches

Abnormal results may include the following:

myopia, or nearsightedness, which is the ability to see near objects better than far objects

astigmatism, or blurred vision

hyperopia, or farsightedness, which is the ability to see far objects better than near objects

presbyopia, or an inability to focus on near objects that often occurs in middle-aged persons

color blindness, which is an inability to see certain colors

blocked tear duct, or a blockage in the tube that carries tears away from the eye

cataracts, or a clouding of the lens in the eye that can cause vision problems

eye trauma or injury

lazy eye, an eye movement disorder also called strabismus

eye diseases

glaucoma

damage to the optic nerve, blood vessels, or fundus

scratches or defects on the cornea