Autorefractor

Autorefractor

An autorefractor or automated refractor is a computer-controlled machine used during an eye examination to provide an objective measurement of a person's refractive error and prescription for glasses or contact lenses. This is achieved by measuring how light is changed as it enters a person's eye.

The automated refraction technique is quick, simple and painless. After application of a cycloplegic agent to keep the ciliary muscle in relaxed position and avoid the errornous diagnosis of a pseudomyopia, the patient takes a seat and places their chin on a rest. One eye at a time, they look into the machine at a picture inside. The picture moves in and out of focus as the machine takes readings to determine when the image is on the retina. Several readings are taken which the machine averages to form a prescription. No feedback is required from the patient during this process.

Within seconds an approximate measurement of a person's prescription can be made by the machine and printed out or shared electronically with an Automated Refraction System.

In some offices this is used to provide the starting point for the optometrist in subjective refraction tests. Here, lenses are switched in and out of a phoropter 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 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 can result in significant overestimation of myopia.

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