3.1: Initial screening

School-based screenings aim primarily at detecting significant refractive errors in children and dispense glasses to those who need them. Clear criteria should be established for testing and prescription of glasses to optimise compliance and cost-efficiency of the programme. Even if WHO’s recommended distance vision indicator (eREC) is 6/12, school-based screenings should aim for a VA cut-off of 6/9 considering the excellent visual potential of children. However, a lower cut-off may lead to a higher false positive rate and therefore increase costs of the programme ⁵.

While myopia and astigmatism will affect distance VA, hyperopia is much more difficult to detect in a school-setting. In fact, there is no consensus yet on whether to screen children for hyperopia, but testing visual acuity with a +2.00 lens is recommended in these guidelines.

Screenings should also include identification of common eye conditions of childhood such as eye infections (conjunctivitis), lid infections (styes) and allergies (allergic conjunctivitis; vernal catarrh). Even if these conditions may not affect the visual acuity, they may keep children away from school or interfere with learning. Other more serious eye conditions which need to be detected and referred to an eye care provider for management include strabismus (in-turning or out-turning eyes), cataracts and amblyopia.

Distance visual acuity

Should be done with usual correction
Monocular (right then left eye)
Cut-off :
- 6/9 is recommended but may lead to more false positive
- 6/12 can be acceptable if resources are limited
Chart
- One isolated row of five age-appropriate optotypes of 6/9 (approximately 0.2 logMAR) with crowding bars (AAO screening guidelines)
- Appropriate test distance (minimum of 3 meters)
- High contrast black on white should be used, with crowding bars
- Mobile phone technologies can be used if validated in children
Failure of screening is defined as a child sees 3 or less of the 5 letters.

Visual acuity with +2.00 lens (hyperopia screening)

Distance visual acuity is measured with child wearing a pair of +2.00 D glasses for at least 1 minute to release the accommodation
A child fails if they are able to pass the 6/9 screening chart with the +2.00 D glasses on or if there is no decline of VA with their existing correction

External eye examination

Use of torch light for examination of external structures. Any child presenting an ocular health problem in one or both eyes should be seen for detailed examination:
- Cornea not transparent
- Pupil not round and black
- Eyes are red with discharge
- White patch on the conjunctiva (Bitot’s spot)

Who should do the screenings?

Screening can be undertaken by health care professionals or non-health care personnel who have been trained and who have demonstrated high levels of competency in all the steps involved (i.e., gives adequate explanation; asks the child if they already wear spectacles; ensures adequate lighting and test distance; tests each eye separately; correctly records the findings as pass or fail for each eye), and interprets the findings correctly and identifies children who require refraction.
Trained teachers are typically recommended as screeners, given their direct time in the class room and familiarity with the children, and builds ownership. There is significant evidence that shows that teachers are able to accurately measure and correctly identify children with vision impairment ^34-36.
However, recent studies have shown that work overload, insufficient training and lack of time can compromise the efficacy and increase the cost of screenings by teachers ^34-36. Community-level health workers such as school nurses, allied health trainees or vision technicians showed better overall outcomes and should be considered as primary screeners ^37-40.

Distance visual acuity

Visual acuity with +2.00 lens (hyperopia screening)

External eye examination

Who should do the screenings?

Useful tools

Example clinical vision screening protocol

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