Introduction: Prevalence of visual impairment is estimated at 15% at the age of 5 years. Early visual screening is essential to prevent the risk of amblyopia and treat strabismus. The Maternal and Infant Welfare department of the Hauts-de-Seine district (France) organized a systematic visual screening during a routine health check-up in 3- to 4-year-old preschool children. In this population, 4% of children were wearing corrected lenses before check-up and 12% of children were referred to an ophthalmic consultant. The aim of this study was to document the performance and limitations of two visual acuity measurement tests: the Stycar test (separated presentation of letters) and Cadet letters test (grouped presentation).
Patients and methods: Twelve physicians conducting check-ups in 56 of the department's preschools constituted two random samples of representative children. The first sample of 201 children included 3- to 4-year-olds with a positive visual screening on the Cadet or Stycar test and the results and recommendations were collected. The second sample included 238 children who had a first negative visual screening at 3-4 years old with the Stycar test. We then conducted a second visual screening at 4-5 years-old with the Cadet letters test and collected results.
Results: In the first sample of 201 children, 73 were lost to follow-up, 40 had a normal documented ophthalmic examination, 63 needed glasses and 25 needed follow-up. The positive predictive value (PPV) of the Stycar test was much higher than the PPV of the Cadet test (79% versus 48%, p<10-4). After this first screening, prevalence of visual impairment at 3-4 years old was estimated at 8%. In the second sample of 238 children, four children were recently lens adapted and 36 were referred to an ophthalmic consultant. Of these 36 children, 11 were lost to follow-up (of these children, two had a very low visual acuity (2/10 and 3/10), four had a normal ophthalmic examination, 13 needed glasses, and eight needed a follow-up. Of the total sample, 10.5% of the children had a documented visual insufficiency on the primary Stycar test screening. The PPV of the Cadet letters test was 84% (IC95%[70%; 98%]). Results of the Cadet letters test was independent of the delay between the two tests.
Conclusion: Although one-third of the children did not follow the recommendations for follow-up consultation, we demonstrate that visual acuity evaluation was insufficient at 3-4 years of age, and the problems were caught at 4-5 years of age with the Cadet test. Physicians must be aware of the difficulty of the Cadet test at 3-4 years of age but also that screening is inadequate when the Stycar test is normal. A second visual screening, taking into account separating problems on the Cadet test is justified at 4-5 years of age The Stycar test must be discontinued after 4-5 years of age when compliance and the predictive value of the Cadet letters test become excellent.