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Measurement of the validity of a preschool vision screening program
B Robinson1, W R Bobier, E Martin
1School of Optometry, University of Waterloo, Ontario, Canada.
Objectives:
The validity (sensitivity and specificity) of a preschool vision screening program was measured over a 3-year period to determine how well strabismus and significant refractive errors could be detected.
Methods:
Public health nurses were trained to administer tests of visual acuity, stereoacuity, and ocular alignment. Failure on any test, visual acuity of 6/9 or less, stereoacuity of less than 100 seconds of arc, or an apparent misalignment of the eyes resulted in referral to an eye care practitioner. An age-matched control was also referred. Analysis of practitioner reports used predefined study-based criteria for ocular abnormalities.
Results:
More than 1100 children were screened each year. The annually calculated prevalence of vision problems ranged between 10.5% and 13.8%. The estimated sensitivity varied from 60.4% to 70.9% (specificity, 69.6% to 79.9%). The yield indicated that a very high percentage of children with vision problems were identified for the first time.
Conclusions:
The validity of this screening is comparable to that of other school screenings. The limitations are predictable. Consideration should be given to replacing visual acuity tests with a rapid, objective measure of refractive error and ocular alignment.
