Objective Vision Screening Device Overview

During the preschool age period (up to 6 years), the most common ocular conditions are strabismus, anisometropia, and high bilateral uncorrected refractive error such as hypermetropia and astigmatism.  All of these, if untreated, can produce amblyopia.  Traditional techniques for preschool screening involve optotype-based evaluation of visual acuity and a cover test for strabismus.  However, such screening is difficult in the pediatrician’s office and is therefore often not performed until at least 3.5 years of age, if at all.  Thus, prior to this age a child is at risk for the development of amblyopia and cannot be detected.  While some studies have demonstrated the ability of traditional acuity screening to detect amblyopia in 3 year old children, most do not show good success rates until at least age 4.

Recent developments in technology and the desire to detect abnormalities before they cause amblyopia have led to the development of new instruments for preschool vision screening.  Primarily, these instruments involve either automated retinoscopy or photoscreening.  There are several instruments which are commercially available and which have various levels of validation.  The purpose of this paper is to review the current validation data regarding these instruments recognizing that this is a rapidly evolving field.

A major difference between traditional acuity screening and the newer methodologies for vision screening is that the former detects decreases in acuity directly, while the latter detects problems that may lead to decreased visual acuity.  These problems have been termed “amblyopia risk factors” and include high uncorrected refractive error (hypermetropia & astigmatism), high myopia, and anisometropia.  The detection of amblyopia risk factors rather than direct detection of decreased acuity is a limitation of these newer technologies; the natural history of amblyopia is unknown and as a result, these technologies over-refer children since some children who are at risk for amblyopia may never in fact develop it.