Of the near magical tools an optometrist uses to determine the best prescription for your vision, the autorefractor is at the top of the list. An autorefractor or automated refractor is a computer-controlled machine designed to provide an objective measurement of a person's refractive error. With this measurement in hand, your eye doctor can dial in the best prescription for glasses or contact lenses to correct the refractive error and improve your vision to as near 20/20 as possible.

Vision is all about light. The autorefractor measures how light is bent as it enters the eye. This is achieved by measuring how light is changed as it enters a person's eye. Refractive error is the eye’s ability to bend light and focus it onto the retina. Complications with the eye’s ability to bend light results in nearsightedness, farsightedness, and astigmatism.

The Technology of Autorefraction

Autorefractors work by shining a beam of light into the eye and measuring how light “reflects” off the back of the eye. That reflection is used to determine the refractive error. The machine calculates the reflection and changes in the retina necessary to bring an image, essentially light, into focus.

The autorefractor process is repeated several times, each time calculating the refraction of the eye necessary to bring the image into focus. The machine uses this information to determine the best prescription for corrective lenses if needed.

The entire autorefractive process is noninvasive, completely painless, and takes no more than a few minutes to complete.

The Optometrist’s Toolbox

The autorefractor along with the two other machines used at the start of an eye exam, is just one tool in the optometrist’s toolbox. While the autorefractor provides invaluable information, the machine alone is not the final authority on a patient’s prescription.

Most optometrists will use the information provided by the autorefractor as a starting point for their more comprehensive eye exam using the phoropter in the exam room. Patients are often very familiar with the phoropter, the machine where lenses are switched back and forth while the patient is asked “which looks better”.

This process is considerably streamlined by using the information provided by the autorefractor and working from there to further determine the most precise prescription possible.

Also in the optometrist’s toolbox is the Ocular Response Analyzer or Auto Tonometer, which we’ll dive into next month.

Reach out to your eye doctor to set up an appointment and get the best prescription for your vision possible.