Screening for amblyopia risk factors in pre-verbal children using the Plusoptix photoscreener: a cross-sectional population-based study

Abstract

Aims: To evaluate the accuracy and applicability of Plusoptix photoscreener in screening pre-verbal children at risk of amblyopia.

Methods: In this cross-sectional population-based study 996 children aged 6-36 months were screened with the Plusoptix. The children underwent complete examinations that included a manual cycloplegic retinoscopy, slit lamp examination, cover test, the Hirschberg test and an assessment of fixation pattern. In addition, the prevalence of amblyogenic risk factors was estimated, the Plusopix measurements were compared with cycloplegic retinoscopy, and the referral criteria were modified to improve the accuracy of the device.

Results: Amblyogenic hyperopia >+3.50 D, myopia >-3.00 D, astigmatism >1.50 D in the orthogonal meridian or >1.00 D in the oblique meridian, or anisometropia >1.50 D was detected in 4.7%, 0.0%, 12.3% and 0.5% of the samples, respectively. The average difference between retinoscopy and photorefraction for spherical equivalence was -0.16 ± 1.0 D (p<0.05). Testability was 98.1% for the Plusoptix. The Plusoptix vision screener referred 47.8% of these children for sensitivity, specificity, positive predictive value and false-negative rates of 100%, 38.7%, 19% and 100%, respectively. These same measurements with the modified referral criteria (hyperopia ≥ 2.00 D in children under 12 months and astigmatism ≥ 1.25 D) were 93.6%, 51.2%, 21.7% and 98.2%.

Conclusion: The Plusoptix is a useful objective screening instrument, but still has low specificity for detecting amblyopia risk factors in the paediatric population.