What tests are part of an eye exam?
Reading those letters from the chart on the wall may be the most familiar test. It is checking your visual acuity, or the sharpness of your vision.
The wall chart is used to check your distance vision and a small, hand-held chart is used to check your near vision.
2. Light in your eyes
The doctor will hold a device to his eye that looks like a flashlight, only held upright. The device is a retinoscope.
He shines the light off the back of your eye to determine whether your vision is 20/20, whether you can better see things that are near you, or better see things that are far away.
The retinoscope is mainly for estimating your vision correction needs, but sometimes the doctor can tell your prescription just from this device.
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3. Better 1, better 2
Another test involves putting your eyes up to a thick device containing lenses. It is called a phoropter. The doctor will have you stare at a distant object while changing lenses, often asking you “better 1, better 2, or the same” to tell whether different lenses better help you see the object.
The phoropter focuses in on your prescription. An autorefractor essentially does the same thing with great accuracy, but it is faster. That can be a benefit with young children, those with difficulty answering which lens works better or those who might not tolerate sitting through a longer refraction process.
4. Eye shapes
The outside of your eye may not be perfectly curved. The eye’s surface, or cornea, can be measured with a device that looks like a telescopic lens.
The keratometer will measure the surface and help the doctor determine how to correct for astigmatism, which is the variations in the cornea’s shape.
5. Little puff of air
Checking your inner eye pressure with a puff of air tests for glaucoma, a common disease that can slowly take your sight. Early detection and treatment can slow or stop the disease.
During this test, you will rest your chin on the tonometry machine, stare at the light and a puff of air will measure the pressure inside your eye.
Glaucoma offers little warning before severe vision loss, so regularly scheduled tests are important.
6. Flashes of light
Testing your peripheral vision and for blind spots typically involves putting your face into the opening of what looks like a giant ping-pong ball.
You focus on a center light and pinpoints of light flash around the inside of the white dome, with you pressing a trigger every time you see a flash.
7. Color blindness test
Those circles that appear to be filled with colored bubbles and a figure formed by a set of differently colored bubbles are part of the test for color blindness.
Color blindness may be genetic, or it may signal another problem is developing.
8. 3-D vision
Depth perception and your eyes’ ability to work in harmony is the point of the stereopsis test.
During this test, you will tell the doctor which letter or shape appears to be raised or floating on the screen.
9. Cover test
Many tests can check to see if your eyes are working together, but the simplest involves a paddle used to cover one eye at a time as you focus on a small item across the room and then at something close.
10. Follow the target
As part of this test, you will hold your head still and the doctor will have you follow a slowly moving light or other object with your eyes. The doctor is looking for smooth movement of the eyes.
Another test will look for your ability to quickly focus between two objects held at a distance from one another, which will detect potential for eye strain or potential problems reading, during sports or other tasks.
11. Look deep into my eyes
Eye doctors can look deep into the structure of your eyes with a microscope called a slit lamp. You place your forehead and chin into the rests on the instrument and the eye doctor uses a bright slit of light to examine your eyelids, cornea, conjunctiva, iris, and lens.
The eye doctor can add a hand-held lens and peer deeper still into the eye, seeing the retina and optic nerve.
12. Wide-open eyes
Drops used to open up your pupils allow the eye doctor to better see the health of your eye structures. While important, dilation can be an inconvenience because your eyesight is affected for several hours.
There are alternatives. Retinal imaging is a quick digital scan of your eye. It produces an image that your doctor can closely examine.
13. Contact lens fittings
If you are interested in contact lenses, it usually means a second visit after your basic eye exam.
The contact lens fitting includes specific measurements and some tests may be repeated from the basic exam for accuracy. The fitting does not require dilation.
After an eye exam, you get a prescription
Now you know the parts — the tests, if you will — of a comprehensive eye exam. While the first six are part of a routine eye exam, you might think of the others as extra credit.
And to continue the exam analogy, many people graduate with a vision prescription for eyeglasses or contact lenses to correct their vision.
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Page published on Friday, January 10, 2020