What’s this test? The phoropter

If you’ve ever had an eye exam, chances are good that you’ve been asked to look through a device where the optometrist flips through different lenses, asks you to look at an eye chart and maybe asks you which lens you prefer, “one or two.” That device is called a phoropter.

A phoropter is a device used to assess refractive error – conditions that make your vision blurry, whether because you’re nearsighted (myopic), farsighted (hyperopic) or have astigmatism. Astigmatism means some part of your cornea or lens isn’t perfectly round or dome-shaped, making your vision (or part of it) blurry or distorted at any distance. All these forms of refractive error can generally be corrected with glasses or contact lenses.

A phoropter is essentially a box full of lenses that makes it easy to try different corrective lenses on a patient. The many dials and buttons allow the optometrist to adjust the power of the lenses.  

A phoropter is used during most eye exams, anytime an optometrist wants to assess your prescription or decide whether you need a prescription for glasses or contact lenses. A phoropter is used on patients approximately from school age through to seniors.

If patients have trouble sitting still or sitting upright, whether because they’re very young or have special needs, an optometrist might instead use a trial frame – glasses that allow different lenses to easily be slotted in and removed.

For patients of any age, an optometrist might use a phoropter and then also a trial frame to assess the final prescription in a more naturalistic way.

Not necessarily. Many people have a small amount of refractive error – i.e. you might be just slightly nearsighted or farsighted or have a small amount of astigmatism – but it doesn’t always require correction. The phoropter helps the optometrist assess exactly what your prescription is and whether it’s significant enough to require glasses or contact lenses. Your optometrist might decide your vision doesn’t need correction yet but to keep an eye on any changes that might occur.

If you’ve never had to look through a phoropter, it might feel a little strange. However, you’re not actually enclosed, nor is your movement restricted. You’ll just be asked to look through the eye holes, sometimes one eye at a time, sometimes with both eyes. You’ll be asked to read letters on an eye chart (which may be seen through a screen or mirror) and you’ll be given options to evaluate what lens gives you clearer vision.

Usually an optometrist will evaluate your distance vision using the phoropter, then evaluate your near vision with or without the phoropter.

To evaluate your near vision using the phoropter, the optometrist will use what’s called a reading rod. It presents text and/or shapes and can be placed at different distances from the eye.

No, there’s really nothing to do in advance. The most important thing during the eye exam is to ensure you’re sitting comfortably as you’re looking through the phoropter, with your head against the forehead rest and your view through the holes unobstructed.

The optometrist will ask you for your input to fine-tune your prescription. They will use labels such as one or two, or possibly three, four, five or six, just to give you a convenient way to say which option helps you see better. You don’t need to remember from one question to the next what the previous “one” or “two” was.

If you don’t see any difference between the options, feel free to say so. You really can’t choose “wrong.”

An optometrist will often use more than one tool to evaluate your vision. They will commonly use a retinoscope and/or autorefractor to initially get close to your prescription and then use a phoropter to refine it with your input.

A retinoscope is a handheld instrument that shines a beam of light into one eye at a time. The optometrist can use the retinoscope to manually evaluate your refractive error by observing how light bends in your pupil as the light is moved back and forth. An optometrist may use a retinoscope without the additional step of the phoropter on patients who have difficulty sitting still, understanding directions or communicating preferences, or who may be intimidated by a larger instrument.

An autorefractor is a device a patient looks through to see an image, often of a hot air balloon, which may go in and out of focus during the test. An autorefractor automatically measures your refractive error based on how light bends as it hits your eye. The hot air balloon (or other image) is just there to give your eyes something to focus on. Like a retinoscope, an autorefractor may be used alone on patients who have difficulty using a phoropter.

Other instruments are used during an eye exam, such as a slit lamp, which shines a light in your eyes like a retinoscope but isn’t handheld. Most of these instruments are used to evaluate your eye health rather than your prescription.

If you have your eyes dilated during an eye exam, a phoropter may produce slightly different results compared to if your eyes aren’t dilated. However, the optometrist knows this and adjusts for it.

For children or young adults, an optometrist will often use eye drops that make it more difficult to focus up close before making evaluations with a phoropter. These drops also dilate the pupils. This is done because young people’s eyes focus very strongly and quickly, which makes it more difficult for the optometrist to obtain a complete picture of their prescription.

The optometrist will finalize your prescription and may recommend you use it to get (new) glasses or contact lenses – or perhaps not, if your prescription is too slight to require the use of corrective lenses or if there has been little or no change since your previous prescription.  

The optometrist will likely also do further tests during your eye exam to evaluate your eye health. These may be done before or after the phoropter is used.

If the patient is a child with myopia (nearsightedness), they may be referred for myopia control treatment.

A phoropter is used as part of a comprehensive eye exam, so there is no additional charge for its use. A comprehensive eye exam costs $120 as of 2025. Discounts are available for University of Waterloo employees and students. Fees are subject to change.

Comprehensive eye exams are available at both the Waterloo and Kitchener clinic locations. Both locations also have an optical dispensary, where you will be able to choose frames and order glasses if necessary. If you would prefer contact lenses, you will be referred to our Advanced Contact Lens Service.

• What you should know about: Myopia
• Volunteer in our research
• Volunteer in Centre for Ocular Research & Education (CORE) research (mostly related to contact lenses)

Article and video by Karen Kawawada

Reviewed by Dr. Natalie Hutchings, BSc, PhD, MCOptom