Common Instruments Used During Eye Exams

Regular eye exams allow you to monitor your vision and eye health. They do more than determine if you need to update your eyeglasses or contact lenses. Routinely seeing an eye specialist goes a long way in detecting early signs of vision-threatening eye conditions like glaucoma and macular degeneration.

Eye doctors use different instruments to examine your vision and the condition of your eyes. Here are some of the most common tools used during eye exams.

Most Frequently Used Tools During Eye Exams

Snellen Chart

Visual acuity measures how well you can see at various distances and is expressed as a fraction. Eye doctors often measure it using a Snellen chart. It contains several rows of letters that get lower towards the bottom. If you have a 20/50 vision, you must be 20 feet away to see something that people can typically see from 50 feet away.

Your specialist will ask you to sit or stand at a distance from the chart and cover one eye with your hand or a small paddle. With the uncovered eye, you’ll read each row of letters and repeat the procedure with the other eye. You’ll usually have to read smaller and smaller letters until you can no longer recognize the characters.

If your vision acuity isn’t 20/20, you may need to wear prescription glasses or contact lenses. You might also have an eye infection, injury or other condition that requires treatment. After a series of tests, your eye doctor will discuss the results and if you need treatment or vision correction.

Phoropter

You might notice a large device in your local eye clinic. It is called a phoropter, which allows your optometrist to determine your eye prescription. They will ask you to sit behind the phoropter and read the eye chart through the lenses. Your doctor will switch the lenses with different optical powers and ask which one gives you the clearest vision. They will then come up with a prescription based on your answers.

Retinoscope

A retinoscope helps eye doctors prescribe the ideal corrective lenses to their patients. This tool is used to illuminate light into the eye so specialists can see the reflection off the retina. Your optometrist will move the light back and forth across the pupils and observe how well your eyes can focus.

The test involving this device is called a retinoscopy, and it assesses your eyes’ ability to work together. It also lets eye specialists know if you have a refractive error like nearsightedness, farsightedness or astigmatism.

Autorefractor

During your contact eye exam, your doctor might also use an autorefractor. It is a machine that measures refractive errors and eye prescriptions. This device measures how light changes as it enters the eye.

While seated, you’ll have to place your chin on a rest. You’ll then look into the autorefractor, one eye at a time. Through the lens, you will see an image that shifts in and out of focus. While reflections are being made, various measurements determine when the eye is correctly focused.

Ophthalmoscope

An ophthalmoscope is a handheld device used to examine the retina and other inner structures of the eye. Shining a bright light through the pupil provides a detailed view of blood vessels, the optic disk and other crucial eye components. It can help detect glaucoma, macular degeneration and diabetic retinopathy.

Slit Lamp

Also called a biomicroscope, a slit lamp is a microscope with a light that lets specialists examine the cornea, lens, iris and other structures of the eye. Through a special lens, your doctor can also check the back of your eyes and look for signs of abnormalities.

Tonometer

Your eyes require a specific amount of pressure inside them to remain healthy. High eye or intraocular pressure can lead to glaucoma. When left untreated, this eye condition can result in irreversible vision loss.

A tonometer measures eye pressure and can help detect glaucoma. Your doctor will administer numbing drops if they are using a type of tonometer that touches the eye. Some specialists use an air-puff tonometer, which doesn’t necessitate numbing drops.

What to Expect During Your Eye Exam Appointment

Health History Check

One of the first things your optometrist will do is ask about your history of vision or eye problems. They will also inquire about your family’s health history. It will help them understand your risk for developing eye conditions. For instance, children whose parents are nearsighted are also more likely to have myopia.

Visual Acuity Test

During a visual acuity test, your eye doctor will ask you to read letters from the Snellen chart. It will help them find out if you need prescription glasses or contacts. If you already wear corrective lenses, this test will allow your specialist to detect changes in your vision.

Refraction Check

If your eye doctor finds that you need corrective lenses, they will request you to look through different lenses. A refraction test will help determine which lenses give you the sharpest vision.

Eye Health Assessment

Eye doctors use special lights and lenses to check the inside of the eye. Assessing the inner structures of the eye will let your specialist catch signs of eye damage or disease. It will help them look for indications of infection and inflammation.

Additional Tests

Refractive errors and eye conditions are not the only things comprehensive eye exams can reveal. Your eye doctor might also discover signs of other health issues. If this is the case, they might perform more tests and ask you to see a general practitioner. Diabetes, heart disease, hypertension, elevated cholesterol and rheumatoid arthritis are some of the most common conditions detected during eye examinations.