Eye Tests

Routine eye tests are one of the best ways to protect your vision. Knowing who to see for a test, what’s involved in the test and how to prepare for the test will help you get the most out of your visit.

An eye examination is one of the best ways to protect your vision because problems can be detected at their earliest stage — when they’re most treatable. Regular eye tests give your eye care professional a chance to help you correct or adapt to vision changes. And eye care specialists can give you expert tips on ways to reduce eyestrain and how to care for your eyes.

Even if you think your eyes are healthy, you’ll still need an eye test from time to time. Know what to expect during an eye test, who to see for a thorough test and how to prepare.

Who needs an eye exam?

Several factors may determine how frequently you need an eye exam, including your age, health and risk of developing eye problems. Here are some general guidelines to follow for eye health:

Children 5 years and younger

Infants, toddlers and preschoolers should have their vision checked each time they visit their pediatrician. It’s difficult to perform in-depth vision tests on this age group, so for kids under 3, your pediatrician will likely look for the most common eye problems — lazy eye and crossed eyes. Depending on your child’s willingness to cooperate, his or her first more comprehensive eye examination should be done between the ages of 3 and 5. Talk with your pediatrician about when an eye test is appropriate for your child.

School-age children and adolescents

Have your child’s vision checked before he or she enters first grade. If your child has no symptoms of vision problems and you don’t have a family history of vision problems, have your child’s vision rechecked every two years. If your child does have vision problems or you have a family history of vision problems, have your child’s vision re-checked every year. Talk with your child’s eye doctor about what checkup schedule is best for your child.

Adults

If you don’t wear glasses or contacts, have no symptoms of eye trouble, don’t have a family history of eye disease and you don’t have a chronic disease, such as diabetes, that puts you at risk of eye disease, have an eye exam at the following intervals:

  1. Once between ages 20 and 29
  2. Twice between ages 30 and 39
  3. Every two to four years between ages 40 and 65
  4. Every one to two years after age 65

If you do wear glasses or contacts, you’ll need to have your eyes checked yearly. And if you notice any problems with your vision, schedule an appointmentwith your eye doctor as soon as possible. Blurred vision, for example, may suggest you need a prescription change. A sudden increase in the number of floaters — dark spots darting through your vision — could suggest vision-threatening changes to your retina.

People at high risk of vision problems

If you have other health problems or a family history of eye disease, you may need more frequent eye examinations. Check with your doctor to determine how often you need an eye exam if you have fit into any of the following high-risk groups:

  1. A personal or family history of eye disease
  2. A previous eye injury
  3. A disease the affects the whole body, such as diabetes, high blood pressure, heart disease or acquired immunodeficiency syndrome (AIDS)
  4. You were born prematurely
  5. You’re black. Black people have an increased risk of glaucoma

Who gives eye exams?

Three kinds of eye specialists can help you with your goal to maintain or improve your vision. Which specialist you choose may be a matter of personal preference, or one specialist may be best for treating your particular eye concern.

Ophthalmologists

Ophthalmologists are medical doctors who provide full eye care, such as giving you a complete eye test, prescribing corrective lenses, diagnosing and treating complex eye diseases, and performing surgery. Some ophthalmologists limit the range of their services, offering basic eye care and specific surgeries, but refer you to another ophthalmologist for a specialized procedure. Some ophthalmologists perform only specific surgical procedures.

Optometrists

Optometrists can provide many of the same services as ophthalmologists, such as evaluating your vision, prescribing corrective lenses and diagnosing common eye disorders. In many places, optometrists also treat selected eye diseases with drugs. Your optometrist may refer you to an ophthalmologist for more complex eye problems, for special procedures and for conditions requiring surgery.

Opticians

An optician is an eye specialist who fills prescriptions for eyeglasses — assembling, fitting and selling them. Some opticians also sell and fit contact lenses.

What’s involved in an eye exam?

A complete eye exam involves a series of tests designed to evaluate your vision and check for eye diseases. It doesn’t hurt. Your doctor may use odd-looking instruments, aim bright lights directly at your eyes and request that you look through a seemingly endless array of lenses. Each test is necessary and allows your doctor to evaluate a different aspect of your vision. Common tests that you might have include:

External eye exam

Your eye doctor makes a quick check of your eyes using a light to ensure the exterior parts of your eyes are functioning correctly. In an external eye exam, your eye doctor checks:

  1. Your pupils to see if they respond normally
  2. The position and movement of your eyes, eyelids and lashes
  3. Your cornea and iris for clarity and shininess

Eye muscle test

This test examines your eye muscles to ensure they’re functioning properly. Your eye doctor looks at your eyes as they move in six specific directions. Your doctor will ask you to sit still and look forward, using your eyes to follow an object, such as a pen. The eye muscle test is designed to detect any weaknesses or uncontrolled movements in the muscles that move your eyes up and down and side to side.

Visual acuity test

This test measures how sharply or clearly you can see something at a distance. Your doctor will ask you to identify different letters of the alphabet off a chart positioned usually 20 feet away. The lines of type get smaller as you move down the chart. You cover one eye and read aloud, then cover the other eye and read aloud. Your doctor monitors how well you can identify the letters.

Your visual acuity is expressed in a fraction — such as 20/20 vision. The top number refers to your distance from the eye chart, usually 20 feet. The bottom number indicates the distance at which a person with normal eyesight could correctly read the line you read. For example, 20/20 vision means that you can see objects clearly from 20 feet away that a person with normal vision could see clearly from 20 feet away. However, if your visual acuity is 20/50, the line you read correctly at 20 feet could be read by a person with normal vision at 50 feet.

Refraction assessment

Refraction refers to how light waves are bent as they pass through your cornea and lens. A refraction assessment helps your doctor determine a corrective lens prescription that will give you the sharpest vision. If you don’t need corrective lenses, you won’t have a refraction assessment.

Your doctor may use a computerized refractor to measure your eyes and estimate the prescription you need to correct a refractive error. Or he or she may use a technique called retinoscopy. In this procedure the doctor shines a light into your eye and measures the refractive error by evaluating the movement of the light that is reflected by your retina.

Your eye doctor fine-tunes this refraction assessment by asking you to look through a Phoroptor, a mask-like device that contains wheels of different lenses, and judge which combination gives you the sharpest vision. By repeating this step several times, your doctor finds the lenses that give you the greatest possible acuity.

Visual Field Test (Perimetry)

Your visual field is the area in front of you that you can see without moving your eyes. Your eye doctor uses this test to determine whether you have difficulty seeing in any areas of your peripheral vision — the areas on the side of your visual field. A few different tests can assess your visual field:

  1. Confrontation visual field exam. Your eye doctor sits directly in front of you and asks you to cover one eye. You look directly at your eye doctor while he or she moves his or her hand in and out of your visual field. You tell your doctor when you can see his or her hand.
  2. Tangent screen exam. You sit a short distance from a screen and stare at a target at its center. You tell your doctor when you can see an object move into your peripheral vision.
  3. Automated perimetry. Your eye doctor uses a computer program that flashes small lights as you look into a special instrument. You press a button when you see the lights.
    Using your responses to one or more of these tests, your eye doctor makes a map of your peripheral vision. If you aren’t able to see in certain areas, your eye doctor uses the map to help diagnose your eye condition.

Slit-lamp Examination

A slit lamp allows your doctor to see the structures at the front of your eye using a microscope — called a slit lamp because it uses an intense line of light to illuminate your eye. Your doctor uses this light to examine the cornea, iris, lens and anterior chamber of your eye.

When examining your cornea, your doctor may use fluorescein (flooh-RES-ene) dye. The orange dye spreads across your eyes to help your eye doctor detect tiny cuts, scrapes, tears, foreign objects or infections on your cornea. Your eyes’ tears will wash the dye away.

Retinal Examination (Ophthalmoscopy)

A retinal examination — sometimes called ophthalmoscopy or fundoscopy — examines the back of your eye, including your retina, optic disc, choroids and blood vessels. Your eye doctor usually uses special eyedrops to dilate your pupils, opening them wider so he or she can see the back part of your eye. The eyedrops may sting briefly and might cause a medicinal taste in your mouth, as the medication drains from your tear ducts into your throat.

Your eye doctor may use one or more of these techniques to view the back of your eye:

  1. Direct examination. Your eye doctor shines a beam of light through your pupil and uses an ophthalmoscope to see the back of your eye. Sometimes your eye doctor won’t need to use eyedrops to dilate your eyes before this exam. You might see afterimages when your eye doctor stops shining the light in your eyes. This is normal and will go away.
  2. Indirect examination. For this exam you might lie down or recline in a chair. Your eye doctor will hold your eye open and examine each eye with a very bright light mounted on his or her forehead — a bit like a miner’s lamp. This exam lets your eye doctor see your eye in great detail and in three dimensions. Since this light is brighter than that in a direct examination, your chance of seeing afterimages is higher, but is normal.
  3. Slit-lamp exam. In this exam your doctor uses the slit lamp along with the ophthalmoscope to look at the back of your eye. The view through a slit lamp is wider than that in a direct exam, but not as detailed as an indirect exam.

The retinal examination takes five to 10 minutes, but if you’re given eyedrops, the effects won’t wear off for several hours. Your vision will be blurry, and you’ll have trouble focusing your eyes. Make sure you have transportation home, since you won’t be able to drive. Depending on your job, you might not be able to return to work immediately after your exam.

Glaucoma Test (Tonometry)

Tonometry measures your intraocular pressure — the pressure inside your eyes. It helps your eye doctor identify if you have glaucoma, a disease that causes pressure to build up inside your eyes and can cause blindness. Glaucoma can be treated if it’s caught early.

Methods your eye doctor may use to test your eyes for glaucoma include:

  1. Applanation tonometry. This test measures the amount of force needed to temporarily flatten a part of your cornea. Orange dye (fluorescein) is usually put in your eye to help your eye doctor see your cornea. The dye washes out with your tears. You’ll also receive an anesthetic eyedrop. Using the slit lamp, your doctor moves the tonometer to touch your cornea. It won’t hurt, and the anesthetic will wear off within two hours.
  2. Noncontact tonometry. This method uses a puff of air to test the pressure in your eye. No instruments will touch your eye, so you won’t need an anesthetic. You’ll feel mild pressure on your eye, which can be uncomfortable, but it lasts only seconds.

You might have other tests during your eye exam, such as those that may detect certain diseases that you may be at risk of. Your eye doctor will determine which tests you should receive.

How should you prepare for an eye exam?

If you’re seeing a new eye doctor for the first time or if you’re having your first eye exam, expect questions about your vision history. Your answers to these questions help your eye doctor understand your risk of eye disease and vision problems. Be prepared to give specific information, including:

  1. Are you having any eye problems now?
  2. Have you had any eye problems in the past?
  3. Do you wear glasses or contacts now? If so, are you satisfied with them?
  4. What health problems have you had in recent years?
  5. Are you taking any medications?
  6. Do you have any allergies to medications, food or other substances?
  7. Has anyone in your family had eye problems, such as cataracts or glaucoma?
  8. Has anyone in your family had diabetes, high blood pressure, heart disease or any other health problems that can affect the whole body?

If you wear contact lenses, bring them to your appointment. Your eye doctor will want to make sure your prescription is the best one for you. Also be prepared to remove your contacts for certain exams. Tests that use orange dye (flourescein) to temporarily color your eye may permanently dye your contact lenses. You’ll want to take them out before those types of tests.

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