Photoscreener Demonstrates Poor Diagnostic Ability for Detecting Exodeviation

A portable photoscreening device may not be suitable for evaluating exotropia in preschool-aged children due to its low sensitivity in detecting exodeviation, according to research published in Ophthalmic and Physiological Optics.  

The study included a total of 210 children (age range, 3-6 years; 54.3% boys) who visited a single pediatric eye clinic between June and December 2020. Participants underwent photoscreening followed by a comprehensive ophthalmic examination on the same day. Children with exodeviation of 8 prism diopters (Δ) or more in the primary position were confirmed to be positive for exotropia. 

Researchers calculated the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the photoscreener for detecting exotropia and used subgroup analyses based on the angle of deviation (≥25 Δ vs <25 Δ) and fusional control (good/fair vs poor).

A total of 80 children had exodeviation ranging from 8-50 Δ. Of the 80 children confirmed to have exotropia, 23 required referrals for exodeviation (screening-positive) and 57 were screening-negatives. 

The overall sensitivity, specificity, PPV and NPV of the photoscreener in identifying exotropia were 28.8%, 95.4%, 79.3%, and 68.5%, respectively. The photoscreener demonstrated moderately good ability for diagnosing exotropia when the test result was positive (positive likelihood ratio, 6.26), but it was less useful for ruling out exotropia when the test result was negative (negative likelihood ratio, 0.75), according to the report.

Children with true-positive results with the photoscreener showed significantly larger angles of exodeviation (P =.02) and a higher proportion of poor fusional control (P =.004) compared with children with false-negatives. The photoscreener demonstrated low sensitivity in detecting exotropia of 25 Δ or more or poor fusional control (35.2% and 43.6%, respectively) and failed to detect exodeviations in approximately 65% (42 out of 64) of children with significant exodeviation who required strabismus surgery.

The study authors affirm “[p]hotoscreeners have been widely used as effective tools for pediatric vision screening,” but state that “[c]omprehensive eye examinations are recommended for the accurate detection of exodeviations and to avoid missing children with significant exotropia who require treatment.”

Study limitations include a single center design and a study sample strictly consisting of children with prior visual complaints.