Vision screening is an efficient and cost-effective method to identify children with visual impairment, or eye conditions that are likely to lead to visual impairment, so that a referral can be made to an appropriate eye care professional for further evaluation and treatment. Up to 6% of pre-school children will have an ocular or vision defect requiring treatment or follow-up.
Vision screening in Ireland is carried out under the guidance of ‘Best Health for Children’, the screening and surveillance programme of the HSE. Updated guidelines for school-entry screening are due to be published in December 2016.
How is vision screening performed?
There are a number of methods used to screen a child's vision. The method chosen is largely dependent on the age and co-operation of the child being screened and the experience of the examiner.
Best Health for Children recommends the following:
- Observation of visual behaviour.
- Use of clear referral criteria: history of amblyopia or squint in first degree relative AND parental concern.
Primary School Children:
- School entry screening is carried out in all Junior Infants.
- Clear referral criteria: visual acuity of less than 0.2 Logmar in one or both eyes (December 2016).
When testing vision, a linear crowded logMAR test at 3 metres, with an adhesive patch is the ideal, using a letter based test, e.g. Keeler or Sonksen.
When testing, it's important to use a test with 'crowding', for example, a line of letters or pictures, as opposed to a single letter or picture. Amblyopia causes blurring of letters in the centre of the line, but not the outside. Hence, the child may be able to identify a single letter at 6/6, but in reality, may only see 6/18 on linear testing.
It is now recognised that using a Logmar test is a more accurate method of measuring visual acuity. For more information on Snellen and Logmar vision, see here.
Who carries out vision screening?
Best Health for all Children Revisited recommends that ideally, screening should be carried out by orthoptists. However, in most areas, designated school nurses screen during the school year.
For further reading on orthoptist-led screening with particular reference to the U.K., see here.
What kinds of eye problems can be detected on a vision screening?
The main goal of vision screening is to identify children who have or are at risk to develop amblyopia, which can lead to permanent visual impairment unless treated in early childhood. Other problems that can be detected by vision screening include strabismus, cataracts, glaucoma, refractive errors such as myopia, hyperopia and astigmatism, ptosis and other more serious but rare conditions.
At what age should a child have his or her vision screened?
Vision screening is most effective when performed at as young an age as possible. The earlier a problem is detected, the better the chance to obtain maximal vision through appropriate treatment.
What if a child fails his or her vision screening?
If a child fails school entry vision screening, the child should be referred for a comprehensive eye examination at your local eye clinic.
Children who fail the school exit screening are encouraged to attend their local optician.
Best Health for Children is available to view online through the HSE website here.
A comprehensive training programme for public health nurses, area medical officers and school nurses was published in 2005, and is available to view and download as a PDF on the HSE website here.