Page 100 - DISINVESTMENT AND IMPLEMENTATION OF VISION SCREENING TESTS BASED ON THEIR EFFECTIVENESS

CHAPTER 5
used to specific eye screening within the general-health screening examination, (ii) they actively had to omit eye screening in the intervention group and (iii) they had to exclude conspicuous eye disorders and a positive family history for strabismus in the intervention group, all raising their level of attention for eye disorders.
Another weakness of our study is that in a third of the unscreened group (1596 out of 5623 children), it was not explicitly stated that the child indeed had not been screened, because a box had been ticked in the examination record that could denote both adherence to the protocol and no screening or no abnormalities found at screening. However, physicians were questioned about these cases and two-third of physicians declared that eye screening was not performed, in accordance with the protocol.
The sensitivity of the screening was not very much affected by limiting the eye examination to children with something conspicuous or a positive family history.
The preventive CHC physicians, however, also add to the effectiveness by limiting the number of unnecessary referrals, particularly of pseudostrabismus in the studied age group. The possibility to assess the specificity of the screening in this study was limited by the protocol dictating eye examination when anything conspicuous or positive family history was present.
The effectiveness and cost-effectiveness of eye screening has been questioned.10-12 Snowdon and Stewart-Brown concluded that there is a lack of good-quality studies on the natural course of amblyopia, the disability associated with amblyopia and the efficacy of treatment.10 The Institut für Qualität und Wirtschaftlichkeit im Gesund- heitswesen (IQWIG) stated that, due to the small number of studies, the limited quality and the fact that the results were inconsistent and no studies on the potentially harmful aspects of vision screening were available, no robust conclusions could be made whether a benefit of preschool vision screening exists.11 Jill Carlton et al. expressed doubt whether any form of screening would be likely to be cost-effective, because little evidence about the long-term utility effects of unilateral vision loss was found. Small utility effects of bullying would improve cost-effectiveness of early screening.12
Additional data about costs of the screening programme will be needed to assess whether, in the Netherlands, preverbal eye screening at age 6-9 months is cost- effective.
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