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Original article

Diagnostic accuracy of school vision screening


Catherine E. Stewart ,

Department of Optometry & Visual Science, City University, CM466, Tail Building, Northampton Square, London, EC1V 0HB, GB
About Catherine E.

PhD BMedSci (Orthoptics)

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James M. Gilchrist,

Department of Optometry, University of Bradford, Bradford, GB
About James M.


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Paul V. McGraw,

School of Psychology, University of Nottingham, Nottingham, GB
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Barry Winn

Hull York Medical School, University of Hull, Hull, GB
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Aim: Currently, the Department of Health recom­mends vision screening of all children between the ages of 4 and 5 years. The aim of this study was to evaluate the diagnostic accuracy of entry-level school- aged vision screening in the UK. The performance of vision screening protocols and referral criterion (Snellen chart) has been compared with an alter­native screening tool (Crowded logMAR test). Diag­nostic accuracy has been modelled in terms of the screening test and referral criterion.

Methods: A total of 494 children (mean age 5.25 ± 0.28 years) were screened, for the presence of visual anomalies, by school nurses using a Snellen visual acuity chart and Crowded logMAR visual acuity test. Referral was made on the basis of Snellen visual acuity measures using standard NHS protocols (visual acuity 6/9 or worse).

Results: Within the population screened, approxi­mately 14% (n = 68) were referred for further investigation. Of the 68 children referred, over two-thirds were found to be visually normal (false-positive rate of 68%). No false-negatives were identified, indicating that the current screening criterion achieves maximum sensitivity. The Crowded logMAR test at the equivalent referral criteria (0.175 logMAR) also achieved maximum sensitivity but with signifi­cantly (p = 0.0008) fewer false-positive referrals (60%).

Conclusion: Current school nurse screening criteria produce a high percentage of false-positives leading to low referral accuracy. However, current protocols provide maximum sensitivity (no false-negatives) for detecting visual anomalies. In order to retain max­imum screening sensitivity whilst reducing the rate of false-positive referrals, screening programmes should adopt more precise measures of visual acuity in the form of logMAR-based tests.
How to Cite: Stewart, C.E., Gilchrist, J.M., McGraw, P.V. and Winn, B., 2008. Diagnostic accuracy of school vision screening. British and Irish Orthoptic Journal, 5, pp.47–53. DOI:
Published on 01 Jan 2008.
Peer Reviewed


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