Diagnostic performance of the Spot vision photoscreener for the detection of exodeviation in preschool-aged children

Abstract

Purpose: To evaluate the diagnostic performance of the Welch Allyn Spot Vision photoscreener in preschool children for detecting exotropia, the most prevalent type of strabismus among Asian children.

Methods: Children aged 3-6 years were screened using the Spot Vision photoscreener and then underwent a complete ophthalmologic examination on the same day. A child with exodeviation ≥8 Δ in the primary position using the cover-uncover test and the alternate prism cover test was confirmed to have exotropia. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the photoscreener in detecting exotropia were calculated. Subgroup analyses were performed according to the angle of deviation (≥25 Δ vs. <25 Δ) and fusional control (good/fair vs. poor).

Results: Two hundred and ten children were included in this study. Among 80 exotropia-confirmed children, 23 needed referrals for exodeviation (screening-positive) and 57 were proven to be screening-negatives with the photoscreener. The overall sensitivity, specificity, PPV and NPV of the photoscreener for detecting exotropia were 28.8%, 95.4%, 79.3% and 68.5%, respectively. The positive and negative likelihood ratios were 6.26 and 0.75, respectively. Compared with the 57 children with false-negatives (71.3%), those with true-positive results with the photoscreener had significantly larger angles of exodeviation (p = 0.02) and a higher proportion of poor fusional control (p = 0.004). The photoscreener had low sensitivity even in detecting exotropia ≥25 Δ or those with poor fusional control (35.2% and 43.6%, respectively). Approximately 65% (42 out of 64) of the children with a significant exodeviation which needed strabismus surgery were not identified by the Spot Vision Photoscreener.

Conclusions: The Spot Vision photoscreener has low sensitivity for detecting exodeviation. It should not be used alone for assessing exotropia in preschool-aged children.

Keywords: exodeviation; photoscreener; preschool-aged children; vision screening.