Screening for anisometropia in preschool children

A preschool vision screening program was reviewed to evaluate eccentric photoscreening (EP), visual acuity, and stereopsis in identifying anisometropia.

Patients referred by the screening were examined to assess efficacy of the three screening techniques in a population of preschool children. Testability and comparison of screening results to the classification of anisometropia (> or = 1 D) by retinoscopy obtained during a complete examination were evaluated.

Although EP identified 94.5% of the anisometropic children as abnormal, only 27.8% were classified as anisometropic by EP. Of the anisometropic children, 36.1% failed acuity, but only 19.4% failed based on a 2 line or greater interocular acuity difference. Stereopsis correctly identified only 7.3% of anisometropes as abnormal.

The sensitivity of EP in identifying anisometropic children as abnormal was superior to acuity and stereopsis, yet its ability to identify anisometropia specifically was poor. Anisometropia of low magnitude or that masked by the dead zone of the EP system was frequently classified as isometropic. Altering the EP referral criterion and/or taking photographs through adequate power plus lenses may improve the sensitivity for specifically identifying anisometropia. However, caution must be exercised when using EP to examine the prevalence of anisometropia in a population or if used to screen for only amblyogenic refractive errors (i.e., anisometropia), because many anisometropes will be missed, resulting in inaccurate prevalence data and significant underreferrals.