Direct testing superior to automated instruments for preschool vision screening
The measurements from automated instruments used in school vision screenings only approximate refractive error and do not provide distance or near visual acuity, making them inferior to direct testing, according to a position statement endorsed by several professional organizations.
“Historically, the primary outcome metric for childhood vision screening programs has been the measurement of visual acuity using optotypes (letters or shapes/pictures),” Susan A. Cotter, OD, FAAO, of the Southern California College of Optometry and Marshall B Ketchum University, and colleagues wrote. “As a result, the mandated screening forms used in many screening settings are designed solely to document visual acuity.”
Visual acuity and refractive error are distinct measures, according to the authors. Whereas visual acuity is, “determined by the ability of an eye to resolve detail,” at far or near distances, refractive error, “is present when the shape of the eye prevents light from focusing directly on the retina.”
Further, the relationship between the two measures is “not [..] simple:” people with refractive errors can have good visual acuity, and those with no refractive errors can have poor visual acuity.
“Visual acuity cannot be correlated with refractive error except in the context of isolated myopia, and even in that instance, the correlation is not always consistent between eyes or individuals,” the authors wrote.
Therefore, it is “not appropriate” to translate estimated refractive error values to visual acuity measures, the authors wrote.
Instead, future efforts should “encourage the pediatric and public health communities to amend their reporting forms and electronic data capture by adding a field for a ‘pass-refer’ outcome when autorefractor or photoscreening instruments are used in place of direct visual acuity testing for preschool vision screening.”
The position statement was endorsed by the American Academy of Optometry, American Academy of Ophthalmology, American Academy of Pediatrics, American Association for Pediatric Ophthalmology and Strabismus, and National Center for Children's Vision and Eye Health at Prevent Blindness.
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