Page 177 - DISINVESTMENT AND IMPLEMENTATION OF VISION SCREENING TESTS BASED ON THEIR EFFECTIVENESS

Therefore the effectiveness of preverbal, orthoptic vision screening before the age of three years is the central theme of this thesis. It was primarily investigated with a large disinvestment study of the preverbal part of the vision screening, the Optimisation of Amblyopia Screening (OVAS) study. In this study two large sequential birth cohorts, that underwent general health screening, with and without preverbal orthoptic vision screening were compared. The question was whether, and to what extent, omission of preverbal vision screening with orthoptic tests as part of general health screening between the age of 6-24 months would affect the detection of strabismus-, refractive- and combined-mechanism amblyopia and to confirm whether the omission of routine orthoptic vision screening tests between age 6-24 months would have no significant negative impact on the total number of cases and the severity of the detected amblyopia.
Preverbal orthoptic vision screening tests and measurement of VA at age 3-5 years are primarily aimed at the detection of amblyopia. Photoscreening has been recently added to regular vision screening in, for example, Flanders at the age of 1-2 years. Photoscreening aims, however, to detect risk factors for the development of amblyopia, instead of the detection of amblyopia itself. The most important risk factor that can be detected by photoscreening is high refractive error. Early prescription of glasses for high refractive errors that are detected by photoscreening will reduce the prevalence of amblyopia at the age of 4-6 years, but it is unknown to what extent. Photoscreening is beyond the scope of this thesis.
First, we compared the very extensive vision screening programme in the Netherlands with other vision screening programmes in Europe. We developed a questionnaire for a survey. We received answers from 36 countries. We found that vision screening programmes in Europe are very diverse. Large differences exist in age of screening, screening tests used and number of screening tests. In most European countries, infants are screened at age 0-4 months, mainly with inspection of the eyes and the red pupil reflex test. Preverbal vision screening with orthoptic tests at age 6-30 months is also (partially) performed in most European countries, but these tests are rarely performed by orthoptists. This preverbal screening consists of a combination of two or more of the following tests; inspection of the eyes, fixation, red reflex testing, Hirschberg test (cornea light reflex), Bruckner test, Cover test, pupillary reflexes, monocular pursuit and motility. In all European countries VA is measured to detect amblyopia with high sensitivity and specificity, but the age of the first measurement varies between three and seven years of age. In a third of countries VA is tested once, in one third twice
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General discussion
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