An eye exam involves a series of tests to evaluate your vision and check for eye diseases. Your eye doctor may use a variety of instruments, shine bright lights directly at your eyes and request that you look through an array of lenses. Each test during an eye exam evaluates a different aspect of your vision or eye health.
An eye exam helps detect eye problems at their earliest stage — when they're most treatable. Regular eye exams give your eye care professional a chance to help you correct or adapt to vision changes and provide you with tips on caring for your eyes.
Several factors may determine how frequently you need an eye exam, including your age, health and risk of developing eye problems. General guidelines are as follows:
For children under 3, your pediatrician will likely look for the most common eye problems — lazy eye, crossed eyes or misaligned eyes. If there are eye concerns or symptoms, an examination is appropriate at that time regardless of age. Your child could undergo a more comprehensive eye exam between the ages of 3 and 5.
Have your child's vision checked before he or she enters first grade. If your child has no symptoms of vision problems and no family history of vision problems, have his or her vision rechecked every one to two years. Otherwise, schedule eye exams based on the advice of your eye doctor.
In general, if you are healthy and you have no symptoms of vision problems, have your eyes checked on this schedule:
Have your eyes checked more often if you:
There are three different types of eye specialists. Which specialist you choose may be a matter of personal preference or will depend on the nature of your eye problem.
If you wear contact lenses or glasses, bring them to your appointment. Your eye doctor will want to make sure your prescription is the best one for you.
If your eyes are dilated as a part of your eye exam, you may want to bring sunglasses to wear after your eye exam is complete, as daylight or other bright lights may be uncomfortable or cause blurred vision. Also, consider having someone else drive you home.
If you're seeing a new eye doctor or if you're having your first eye exam, expect questions about your vision history. Part of the examination, such as taking your medical history and the initial eye test, may be performed by a clinical assistant or technician.
Your answers help your eye doctor understand your risk of eye disease and vision problems. Be prepared to give specific information, including:
An eye exam usually involves these steps:
Several different tests may be performed during the eye exam. The tests are designed to check your vision and to examine the appearance and function of all parts of your eyes.
At the end of your eye exam, you and your doctor will discuss the results of all testing, including an assessment of your vision, your risk of eye disease and preventive measures you can take to protect your eyesight.
This test evaluates the muscles that control eye movement. Your eye doctor watches your eye movements as you follow a moving object, such as a pen or small light, with your eyes. He or she looks for muscle weakness, poor control or poor coordination.
This test measures how clearly you see. Your doctor asks you to identify different letters of the alphabet printed on a chart (Snellen chart) or a screen positioned some distance away. The lines of type get smaller as you move down the chart. Each eye is tested separately. Your near vision also may be tested, using a card with letters similar to the distant eye chart. The card is held at reading distance.
Light waves are bent as they pass through your cornea and lens. If light rays don't focus perfectly on the back of your eye, you have a refractive error. Having a refractive error may mean you need some form of correction, such as glasses, contact lenses or refractive surgery, to see as clearly as possible.
Assessment of your refractive error helps your doctor determine a lens prescription that will give you the sharpest, most comfortable vision. The assessment may also determine that you don't need corrective lenses.
Your doctor may use a computerized refractor to estimate your prescription for glasses or contact lenses. 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 reflected by your retina back through your pupil.
Your eye doctor usually fine-tunes this refraction assessment by having you look through a masklike device that contains wheels of different lenses (phoropter). He or she asks you to judge which combination of lenses gives you the sharpest vision.
Your visual field is the full extent of what you can see to the sides without moving your eyes. The visual field test determines whether you have difficulty seeing in any areas of your overall field of vision. The different types of visual field tests include:
Using your responses to one or more of these tests, your eye doctor determines the fullness of your field of vision. If you aren't able to see in certain areas, noting the pattern of your visual field loss may help your eye doctor diagnose your eye condition.
You could have poor color vision and not even realize it. If you have difficulty distinguishing certain colors, your eye doctor may screen your vision for a color deficiency. To do this, your doctor shows you several multicolored dot-pattern tests.
If you have no color deficiency, you'll be able to pick out numbers and shapes from within the dot patterns. If you do have a color deficiency, you'll find it difficult to see certain patterns within the dots. Your doctor may use other tests, as well.
A slit lamp is a microscope that magnifies and illuminates the front of your eye with an intense line of light. Your doctor uses this device to examine the eyelids, lashes, cornea, iris, lens and fluid chamber between your cornea and iris.
Your doctor may use a dye, most commonly fluorescein (flooh-RES-een), to color the film of tears over your eye. This helps reveal any damaged cells on the front of your eye. Your tears wash the dye from the surface of your eye fairly quickly.
A retinal examination — sometimes called ophthalmoscopy or funduscopy — allows your doctor to evaluate the back of your eye, including the retina, the optic disk and the underlying layer of blood vessels that nourish the retina (choroid). Usually before your doctor can see these structures, your pupils must be dilated with eyedrops that keep the pupil from getting smaller when your doctor shines light into the eye.
After administering eyedrops and giving them time to work, your eye doctor may use one or more of these techniques to view the back of your eye:
Tonometry measures the fluid pressure inside your eye (intraocular pressure). This is one test that helps your eye doctor detect glaucoma, a disease that damages the optic nerve.
Several methods to measure intraocular pressure are available, including:
If your eye pressure is higher than average or your optic nerve looks unusual, your doctor may use a pachometer. This instrument uses sound waves to measure the thickness of your cornea. The most common way of measuring corneal thickness is to put an anesthetic drop in your eye, then place a small probe in contact with the front surface of the eye. The measurement takes seconds.
You may need more-specialized tests, depending on your age, medical history and risk of developing eye disease.
During a common test for visual acuity, your doctor has you read from a Snellen chart to determine how well you can see letters at a distance.
During a refraction assessment, your doctor asks you to look through a masklike device (phoropter) that contains wheels with different lenses having different strengths to help determine which combination gives you the sharpest vision.
During manual Goldmann visual field testing, you look at a testing screen on which small spots of light come into your field of view. You press a button each time you see the light spot and your response is mapped by a technician. Your doctor evaluates this map, which helps identify defects in your field of vision.