Page 136 - DISINVESTMENT AND IMPLEMENTATION OF VISION SCREENING TESTS BASED ON THEIR EFFECTIVENESS

CHAPTER 7
MATERIALS AND METHODS
This study is part of the Optimization of Amblyopia Screening study that compares two sequential birth cohorts, with and without eye screening tests between 6 and 24 months of age.6,7 In the RAMSES observational birth-cohort study, it had been found that cases of amblyopia detected before age 36 months, were not detected by screening and had strabismus in most cases.1 Moreover, the quality of the screening examinations between 6 and 24 months of age was shown to be moderate in a semi- structured observational study.8
Visual acuity (VA) was measured with the APK (Figure 1) in 36-months-old children at CHC’s. Children born between 1st July 2011 and 30th June 2012 in the region with CHC’s of the family health care providers Icare and the Municipal Health Service in the provinces Drenthe, Gelderland and Flevoland, who were invited for screening at 36 months, were eligible. Youth Health Care (YHC) physicians and nurses of Icare, one of the organisations for preventive health care, screen 8% of the Dutch birth figure. Together with the invitation, parents were sent the APK picture optotypes to practise with their child in advance. VA was measured by YHC physicians or nurses. They receive one day of eye-examination training by a teaching orthoptist every five years. The VA measurement was rated as sufficient VA, insufficient VA or failed measurement (Table 1). The VA measurement was rated insufficient when the VA did not reach the threshold. The VA measurement failed when the measurement carried out by a particular YHC physician or nurse failed, when only binocular VA was measured or when only the VA of one eye was measured. If the child already wears glasses and is under treatment of an orthoptist or ophthalmologist, the VA measurement should only be performed if there is a specific reason to do so, according to the Dutch guideline.3 Data were collected from electronic screening records from the CHC’s.
The Dutch vision screening guideline prescribes retesting after six weeks in case of failed VA measurement and in case of threshold VA designated as “doubtful” VA. This is defined as a VA of one eye of 5/10 or when there is one line interocular difference (not logMAR, however: 5/5, 5/6, 5/10, 5/15, etc.). Note that, according to the current Dutch guideline, a VA 5/6 and 5/5 is designated as “doubtful”. Note also that the interval between 5/10 and 5/6 is approximately 2logMAR lines. If the VA at the retest is not better than the first measured VA, the child is referred. Children with a VA lower than 5/10 for one eye or two lines interocular difference at the first measurement, are referred directly.3 It must be noted however, that for this study, the Dutch guideline
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