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.
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In some offices this process is used to provide the starting point for the ophthalmologist or 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.
- Jorge J, Queiros A, Almeida JB, Parafita MA. "Retinoscopy/autorefraction: which is the best starting point for a noncycloplegic refraction?" Optom Vis Sci. 2005 Jan;82(1):64-8. PMID 15630406.
- Choong YF, Chen AH, Goh PP.: A comparison of autorefraction and subjective refraction with and without cycloplegia in primary school children. Am J Ophthalmol. 2006 Jul;142(1):68-74. PMID 16815252.
- 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. PMID 17659966.
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- Trusit Dave "Automated refraction - Design and applications" in "Optometry Today" 04/06/04