An autorefractor or automated refractor is a computer-controlled machine used during an

eye examination An eye examination is a series of tests performed to assess vision and ability to focus on and discern objects. It also includes other tests and examinations pertaining to the eyes. Eye examinations are primarily performed by an optometrist, op ...

to provide an objective measurement of a person's

refractive error Refractive error, also known as refraction error, is a problem with focus (optics), focusing light accurately on the retina due to the shape of the human eye, eye and or cornea. The most common types of refractive error are myopia, near-sightedne ...

and prescription for

glasses Glasses, also known as eyeglasses or spectacles, are vision eyewear, with lenses (clear or tinted) mounted in a frame that holds them in front of a person's eyes, typically utilizing a bridge over the nose and hinged arms (known as temples or ...

contact lenses Contact lenses, or simply contacts, are thin lenses placed directly on the surface of the eyes. Contact lenses are ocular prosthetic devices used by over 150 million people worldwide, and they can be worn to correct vision or for cosmetic ...

. This is achieved by measuring how light is changed as it enters a person's eye.

Technique

The majority of autorefractors calculate the vision correction a patient needs (refraction) by using sensors that detect the reflections from a cone of infrared light. These reflections are used to determine the size and shape of a ring in the retina which is located in the posterior part of the eye. By measuring this zone, the autorefractor can determine when a patient's eye properly focuses an image. The instrument changes its magnification until the image comes into focus. The process is repeated in at least three meridians of the eye and the autorefractor calculates the refraction of the eye, sphere, cylinder and axis. Modern autorefractors are based on the idea patented by Antonio Medina Puerta.

Uses

In some offices, this process is used to provide the starting point for the

ophthalmologist Ophthalmology ( ) is a surgery, surgical subspecialty within medicine that deals with the diagnosis and treatment of eye disorders. An ophthalmologist is a physician who undergoes subspecialty training in medical and surgical eye care. Followin ...

optometrist Optometry is a specialized health care profession that involves examining the eyes and related structures for defects or abnormalities. Optometrists are health care professionals who typically provide comprehensive primary eye care. In the Uni ...

in subjective refraction tests. Here,

lenses A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

are switched in and out of a

phoropter A phoropter or refractor is an ophthalmic testing device. It is commonly used by eye care professionals during an eye examination, and contains different lenses used for refraction of the eye during sight testing, to measure an individual's ref ...

and the patient is asked "which looks better" while looking at a chart. This feedback refines the prescription to one which provides the patient with the best vision. Automated refraction is particularly useful when dealing with non-communicative people such as young children or those with disabilities.

Retinoscopy

Retinoscopy Retinoscopy (Ret) is a technique to obtain an objective measurement of the refractive error of a patient's eyes. The examiner uses a retinoscope to shine light into the patient's eye and observes the reflection (reflex) off the patient's retina. W ...

performed by an experienced clinician has been found to provide a more accurate estimation of refractive error than autorefraction. Recent studies report that autorefractor measurements without application of cycloplegia medication can result in significant overestimation of

myopia Near-sightedness, also known as myopia and short-sightedness, is an eye disease where light focuses in front of, instead of on, the retina. As a result, distant objects appear blurry while close objects appear normal. Other symptoms may include ...

.Fotedar R, Rochtchina E, Morgan I, Wang JJ, Mitchell P, Rose KA.: Necessity of cycloplegia for assessing refractive error in 12-year-old children: a population-based study. Am J Ophthalmol. 2007 Aug;144(2):307-9. .

References

External links

{{Commons category, Autorefractors * Trusit Dave "Automated refraction - Design and applications" in "Optometry Today" 04/06/0

* "This Company Is Bringing Eye Exams (And Glasses) To People Who Can't Afford Healthcare". Read about Smart Vision Labs in "Business Insider" 09/29/1

* PIKE Ophthalmic, imag

Ophthalmology Ophthalmic equipment