What is a: Phoropter

Phoropter

A phoropter is an instrument used to test individual lenses on each eye during an exam.

If, during an eye examination, your doctor has discovered a vision problem like nearsightedness, farsightedness or astigmatism, it's likely that one of the next steps you'll take will involve a phoropter. A phoropter is special machine used to switch multiple lenses in front of your eyes to correct your vision.

Phoropters look imposing – like space-age visors – but are really an ingenious way to quickly determine the exact vision correction needed by your individual eyes.

By having you look through the phoropter at a visual reference, image, or the “Big E” chart (the Snellen chart), your eye doctor will help guide you toward lenses that correct your vision impairment by switching lenses within the machine on the fly.

How does a phoropter work?

The process of switching lenses in front of your eyes is less involved than it may look, given the imposing nature of the device. A phoropter is used to manually determine “refraction” – exactly how a lens must be shaped and curved to correct your vision to a normal state, nothing more.

Phoropters are subjective however, based on your visual perception and response to your eye doctor's questions. Is your vision better, or worse? With this lens, or this lens? How about now?

There are other procedures and technologies available that automatically measure the refraction needed within your eye and produce a "prescription" measurement without your input. These are called autorefractors and aberrometers.

The information seen here is for reference purposes only and is not intended as medical advice or to diagnose or prescribe any specific treatment(s). For all questions and concerns about your vision, eye health and potential eye problems, please consult an eyecare professional.

Special thanks to the National Eye Institute, National Institutes of Health, for source material that aided in the creation of this website. Visit the NEI/NIH website.

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