Efficacy of Visual Screening in Ontario
Condition: Amblyopia
MeSH terms: Amblyopia
Study type: Interventional

Summary: 
      Amblyopia (lazy eye), is the leading treatable cause of vision loss in childhood. Uncorrected
      refractive errors (ie farsightedness) can lead to difficulties in school. Unfortunately, many
      children do not receive vision screening until they have already developed irreversible
      vision problems. We will conduct a cluster randomized clinical trial in which schools, not
      individual children, are randomly allocated to receive a kindergarten visual screening
      program or to receive no intervention by the research team (i.e., "care as usual"). We will
      compare the prevalence of visual problems (and proportion of children with reading problems)
      when the children are in Grade 2, after allowing for at least one year of treatment.
    

Detailed description: 
      The proposed study is a single-masked cluster randomized clinical trial, with randomization
      and analyses occurring at the level of "schools" (i.e., we are not randomly assigning
      individuals to groups). To assess the efficacy of a visual screening program, we will compare
      visual outcomes in 25 schools randomly chosen to receive the program and 25 schools allocated
      to "care as usual" one year after screening. The screening tools are HOTV crowded acuity,
      Preschool Randot Stereoacuity Test, and Plusoptix Autorefractor. The outcome measures will
      assess later differences between schools receiving the visual screening program and control
      schools for prevalence of (1) visual and (2) reading problems. A lower prevalence of either
      or both problems in schools where the visual screening program was offered would provide
      evidence for the efficacy of vision screening. Primary outcome measure is the prevalence of
      amblyopia, reduced stereo vision, and untreated clinically significant refractive errors in
      "screened" versus "care as usual" schools. Secondary outcome measure is the proportion of
      children performing 1 standard deviation below average on reading scores in "screened" versus
      "care as usual" schools.
    

Intervention name(s): Crowded HOTV Acuity Test; Preschool Randot Stereoacuity Test; Plusoptix Autorefractor; Comprehensive Eye Exam
Intervention type(s): Other; Other; Device; Other
Intervention description(s): This is one of the most sensitive tests of acuity for vision screening of young children. The child is asked to recognize a letter (H,O,T,V) that is surrounded by bars to induce the crowding effects typical of amblyopia. Children were tested monocularly and was required to achieve at least 20/32 in each eye to pass. Children already wearing glasses were tested with their glasses on.; This is a reliable screening test for stereo depth perception for young children. Children wear polarized stereoglasses and are asked to identify or match shapes that are "hiding in the snow", which cannot be perceived if the child has abnormal binocular vision. Children were required to achieve at least 60 arcseconds of disparity to pass. Children already wearing glasses were tested with their glasses worn under the stereo glasses.; Autorefractors are electronic devices that measure refractive errors by focusing a light onto the child's eyes and recording how their reflections from the retina return to the camera. The Plusoptix has been shown to have high sensitivity and specificity in previous research. AAPOS (2013) guidelines were used to determine the referral criteria.; Children who did not pass all three screening tests were referred for full cycloplegic optometry exams, with a parent/guardian present. Optometrists assessed visual history, monocular visual acuity (near & far), strabismus, binocular function, abnormalities of the anterior segment, and cycloplegic refraction. If the optometrist prescribed glasses, frames were chosen at the time of the exam and the glasses were dispensed either at school (with an optician) or at the optometrist's office.
Allocation: Non-Randomized
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Diagnostic