What Happens at Your Eye Exam?

A technician or doctor will do some simple tests. They may ask about your medical history or any vision problems you've had lately. You may get some drops in your eyes, too. If your doctor isn't there at first, they'll meet with you before you leave. Usually, the exam is painless and takes about an hour or so.

You look at a series of letters to find out how sharp your vision is at different distances. The letters usually get smaller as you go on. Typically, you test one eye at a time, then both eyes together. If you have “20/30” vision, that means that standing 20 feet from the chart, you can read letters most people see from 30 feet. So 20/20 would be better, and 20/15 would be even better.

Your pupils are openings at the center of your eyes that get bigger or smaller, depending on how much light you're looking at. To test them, your doctor may shine a bright beam of light into your eye. This should make your pupils shrink. If they get wider, or don’t respond at all, there may be a problem.  

Your doctor will ask you to follow the movement of a small object, like a pen or a light, with your eyes. They'll watch to see how your eyes work together, and they'll look for signs of weakness and poor muscle control. Your doctor will also want to know if you see double as your eyes move around.

This is also called a perimetry test. As you focus straight ahead, your doctor will ask you to let them know as soon as you can see a certain object, like a hand, pen, or blinking light. This will let them know how wide your field of sight is. If your peripheral (side) vision isn't as strong as it should be, it may be a sign of glaucoma. That's a group of eye conditions that can lead to vision loss.

Tonometry measures the pressure of the fluid inside your eye. If yours is too high, it could be a sign of glaucoma. There are two ways this is done: In one, you'd get numbing drops before a tool called a tonometer pushes against the front of your eye. In the other, just a simple puff of air goes into your eye. Neither method should hurt.

Your doctor or technician may show you a series of numbers, letters, or shapes made from lots of small dots of different colors. If you can’t pick out certain patterns, it may mean that you have trouble telling one color from another. Color blindness isn't usually serious, but it can be useful to know if you have it.

Your retina is a light-sensitive layer of cells that line the back of your eye and send signals to your brain. To check it, you'll first get drops in your eye to widen your pupil. That'll let your eye doctor get a good look at both your retina and your optic nerve to see if anything's wrong. You might be oversensitive to light for a few hours after the test while your pupils get back to normal.

A tool called a slit-lamp microscope lights up and magnifies the front of your eye. This gives your eye doctor a close look at your eyelids, eyelashes, and your cornea, the clear, curved front of your eye. The microscope also helps them check your iris (the colored part) and the clear lens behind your pupil that focuses light onto the back of your eye. They'll look for scars, scratches, and cloudiness in your lens called cataracts.  

This can tell if light bends -- or refracts -- correctly through your cornea and lens. The test usually starts with a retinoscopy. Your eye doctor will take measurements as they shine light into your eye. Then, you'll sit behind a machine while they flip through a set of lenses and ask you which ones help you see better. Depending on the results, you may need glasses, contacts, or surgery to correct your vision. 

This isn't part of a routine eye exam. But your doctor might do it if they think you may have glaucoma or other eye problems. It uses ultrasound to measure the thickness of your cornea. You’ll get anesthetic drops in your eye, and a small probe will touch the front of it for a few seconds. A thin cornea could be a sign of glaucoma.

It’s a good idea to get one when you turn 40 to check for vision problems and signs of disease not tied to your sight. Go earlier if you notice eye problems or if you have diabetes, high blood pressure, or a family history of eye disease. After the first exam, your eye doctor can tell you how often to come back. Once you turn 65, you should get an exam every year or so to check for cataracts, glaucoma, or other eye issues linked to age.