Page 111 - DISINVESTMENT AND IMPLEMENTATION OF VISION SCREENING TESTS BASED ON THEIR EFFECTIVENESS

Effectiveness of routine population-wide orthoptic preschool vision screening tests at age 6-24 months in The Netherlands
Data Collection
Child healthcare centre
Vision screening data was collected from the electronic screening records from the CHC centres. The CHC organizations provided an Excel data set to the researchers. The follow-up visits at the CHC also provided information about children referred outside of screening.
Orthoptists
Orthoptists working in the study area were contacted and visited before the start of the study. Treating orthoptists provided clinical orthoptic data if the child was referred based on initials and date of birth. Some orthoptists also provided information about children from the selected cohorts, who were referred outside of screening by others than the CHC centres, like general practitioners or paediatricians. For each first hospital visit of a child in the two study-arms, orthoptists filled out a standardized form about orthoptic examination, VA, diagnosis and treatment (Appendix). The treating orthoptists were asked to indicate whether the child (possibly) had amblyopia and, if amblyopia was suspected, whether it was strabismus, refractive, combined-mechanism or deprivation amblyopia (type of amblyopia).
Received data of the CHC centres were matched with the orthoptic data, provided with initials and date of birth, and thereafter anonymized by the researchers.
Data analysis
If one of the VA measurements (36, 45 or 60 months) at the CHC centre was sufficient according to the national protocol,5 the child was classified as having no amblyopia. If no or one failed or insufficient VA measurement was available, without orthoptic information, the child was classified as lost-to-follow up. If the VA measurement was insufficient twice or had failed twice, and no orthoptic information was available, children were invited for extra VA measurements by the study orthoptist or the 60 months VA measurement result was requested from the CHC centre if available. If no extra VA result could be obtained the child could not be diagnosed as amblyopic or non-amblyopic, but was classified as a separate loss-to-follow group because of a slightly higher chance of amblyopia.
When orthoptic information was available for children who had been referred at an age before VA measurement was possible, the amblyopia presence was based on the opinion of the treating orthoptist: amblyopia present: definitively, probably, probably not or not, fixation preference and the presence of an amblyogenic factor (strabismus, refractive disorder or deprivation).
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