Autorefraction: Objective Estimation of Refractive Error

Uncorrected refractive error is the leading cause of visual impairment and one of the most common causes of avoidable blindness globally [1, 2]. Inaccurately corrected refractive errors also lead to undesirable consequences such as sub-optimal visual resolution, asthenopia, binocular vision anomalies, and amblyopia in children; all of these adversely affect the individual’s quality of life and daily activities [3–5]. Therefore, screening for uncorrected refractive errors and accurate correction is vital in eye care [6]. Identifying and correcting such errors in a typical eye examination are a two-step process, commonly designated as “objective” and “subjective” refraction. This chapter will focus on specific automated techniques commonly used in objective refraction. Their measurement principles, operating ranges, specific use-cases, if any, will be discussed in this chapter. Retinoscopy, the present-day gold standard for objective refraction, against which all other autorefractors are compared will be discussed along with subjective refraction techniques in other chapter(s) of this book.