We are independent & ad-supported. We may earn a commission for purchases made through our links.
Advertiser Disclosure
Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.
How We Make Money
We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently of our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.
Health

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

What is a Phoroptor?

Niki Acker
By
Updated: May 17, 2024
Views: 5,495
Share

A phoroptor is an instrument used by eye care professionals to measure a patient's refractive error in order to determine an eyeglass prescription. Phoroptors can also be used to make other measurements, such as the phoria, or natural resting position of the eye, and the amplitude of accommodation (AA), the eye's ability to focus at near distances. An eye care professional uses a phoroptor to measure a patient's refractive error by letting the patient view an eye chart through the phoroptor, adjusting the phroptor's settings, and asking the patient which settings provide the best vision.

Refractive error is an error made by the eyes in focusing light. A phoroptor is equipped with a series of lenses that refract light and focus images on the patient's retina. As the lenses are adjusted, the degree of correction necessary to address a patient's refractive error can be determined. The optical power of the lenses in the phoroptor, or the degree to which they converge light, is measured in very small increments, 0.25 diopters, in order to determine an accurate eyeglass prescription.

There are three measurements per eye that go into an eyeglass prescription: spherical power, cylindrical power, and cylindrical axis. All three can be measured by a phoroptor. Each eye is different, even in a single patient, so separate measurements must be made for each eye. Therefore, a typical eyeglass prescription consists of six different measurements.

Spherical power refers to the ability of the eye to focus light on the retina. If the spherical power is too high for the length of the eyeball, the patient will be myopic or nearsighted. If the spherical power is too low for the length of the eyeball, the patient will have hyperopia or farsightedness. Cylindirical power and axis are used to measure astigmatism, blurry vision due to the inability of the eye to focus images sharply on the retina.

A phoroptor can also be used to analyze binocular vision, or the way in which the two eyes work together to focus images. Phoroptors are usually fitted with prisms in order to observes and analyze phorias and binocular vision. A phoroptor can measure vertical and horizontal vergences, the simultaneous movement of the two eyes in opposite directions -- towards each other or away from each other -- in order to focus on closer or further objects. Therefore, phoroptors can also be used to treat orthoptic problems, or defects in eye movement.

Share
WiseGeek is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Niki Acker
By Niki Acker
"In addition to her role as a WiseGeek editor, Niki Foster is passionate about educating herself on a wide range of interesting and unusual topics to gather ideas for her own articles. A graduate of UCLA with a double major in Linguistics and Anthropology, Niki's diverse academic background and curiosity make her well-suited to create engaging content for WiseGeekreaders. "

Editors' Picks

Discussion Comments
Niki Acker
Niki Acker
"In addition to her role as a WiseGeek editor, Niki Foster is passionate about educating herself on a wide range of...
Learn more
Share
https://www.wisegeek.net/what-is-a-phoroptor.htm
Copy this link
WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.

WiseGeek, in your inbox

Our latest articles, guides, and more, delivered daily.