Disinvestment Study of Population-Based Vision Screening in Children
Condition: Amblyopia
MeSH terms: Amblyopia
Study type: Interventional

Summary: 
      The purpose of this study is to determine the optimal screening intervals and
      cost-effectiveness of population-based vision screening in preverbal children in the
      Netherlands.
    

Detailed description: 
      Amblyopia (prevalence 3 - 4%)is a preventable, unilateral loss of vision in young children,
      in most cases caused by strabismus (squint) or unilateral hypermetropia (need of plus
      glasses), or both. The sensitive period in which vision loss can develop and be recovered, by
      covering the better eye with a patch, is up to 6 years of age. Population-based programs for
      child vision screening exist in Sweden, the United Kingdom, Canada, eastern European
      countries and the Netherlands. Measurement of visual acuity at age four (preschool) is most
      common. In some countries, including Canada and the Netherlands, preverbal screening of
      visual function in infants and young children (age 0 - 2) has been added to the screening
      program. In the Netherlands, it is applied during the regular visits at ages 1-2, 3-4, 6-9,
      14-24 months. At the age of 36 months, monocular visual acuity is tested with a picture
      chart. At the age of 45 and 60 months, monocular visual acuity is measured with the Landolt-C
      chart. In 1996, the investigators started a follow-up study of a birth cohort in Rotterdam
      (RAMSES) to determine the sensitivity, specificity and effectiveness of the screening
      program. A diagnosis of amblyopia was made in 100 (3.4%) of 2,964 children and was caused by
      refractive error (42), strabismus (19), both combined (30) or deprivation (7). It was found
      that most cases of amblyopia were detected by vision screening with measurement of visual
      acuity from age 3 years onwards. Preverbal screening enabled earlier detection of strabismus
      amblyopia, but not at all of refractive amblyopia.

      The investigators therefore propose a disinvestment study of vision screening, with omission
      of screening at age 6-9 and 14-24 months. First, the optimal screening intervals are
      calculated with a newly developed micro-simulation model for effectiveness of repeated
      screening, on the basis of the data obtained in the RAMSES study. The model simulation
      predicted that screening at age 6-9 and 14-24 months can be omitted without an appreciable
      loss of number of detected amblyopia cases. This will be tested in a RCT among two large
      youth health care organisations, ICARE (12,500 new children annually) and GGD-Amsterdam. Two
      large birth-cohorts will be recruited. Children born between July and December 2011 will form
      our control group and will be examined at 6-9, 14-24, 36 and 45 months. Children born between
      January and June 2012 will be our intervention group. These children will be examined only at
      36 and 45 months.

      Endpoint is the number of cases of amblyopia detected, weighted for visual acuity, against
      age at detection. The question is whether a significant difference between groups can be
      found in the cumulative number of cases of amblyopia detected up to the age of 4 years. The
      new model for optimising screening intervals will be developed further in the course of the
      study into a generic tool for determining optimal screening intervals in any screening
      program with repeated exams for young children and should ultimately allow for comparison of
      effectiveness of population-based screening programs for different disorders in different
      countries, carried out by different personnel. Finally, in the RAMSES study 23% of the
      children screened positively had not been referred successfully to an ophthalmologist or
      orthoptist; 43% of their parents had low to moderate fluency in the Dutch language. This
      reflects lack of utilisation among immigrants of preventive screening and a faltering transit
      from prevention to care. Unsuccessful referral, in relation to parental fluency in Dutch,
      ethnicity and SES will, hence, be monitored in the study in an exploratory fashion.
    

Intervention name(s): Disinvestment protocol
Intervention type(s): Behavioral
Intervention description(s): Omission of population-based child vision screening visits at 6-9 and 14-24 months: Children in the intervention group will not be eye screened at age 6-24 months
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Screening
Keywords: Amblyopia; Vision-Screening