Vision screening and refractive error in children

Childhood vision screening aims to find reduced sight early enough for treatment to support visual development. A child may have substantial unilateral blur without complaining because the other eye supplies an adequate image. Screening tests each eye and can reveal this hidden difference. It is a population programme with a defined test and referral pathway; a full clinical eye examination addresses a broader range of symptoms, ocular health and refractive questions.

The UK National Screening Committee recommends screening children aged four to five. In England, local authorities commission an orthoptist-led service for children in the academic year in which they turn five. The pathway includes children in mainstream state schools, independent schools and home education. Children attending special schools need an alternative assessment appropriate to their development and needs. Provision and access should be checked locally, because a child may not have received screening merely by having started school.

The national test is Keeler Crowded logMAR acuity, performed separately for each eye. The child can match the letters rather than naming them, so reading ability is not required. Crowding bars help identify difficulties that might be underestimated when isolated symbols are used. The standard testing distance is three metres. Prescribed glasses or contact lenses are worn for screening, occlusion must prevent peeping and the score for each eye is recorded independently. A binocular result cannot stand in for two monocular measurements.

Interpret the scale carefully: lower logMAR numbers represent better acuity. The national pathway asks whether both eyes achieve 0.20 or better. An eye scoring 0.30 has poorer acuity and triggers referral, even if the other eye scores 0.00. Reaching exactly 0.20 in each eye meets the pathway threshold when the test is valid. These are screening decisions, not diagnostic labels; a referral does not mean that amblyopia has already been proved or that a particular spectacle prescription is required.

A child who cannot complete the task must not be recorded as passing. The pathway permits one repeat attempt, with referral if testing is again unsuccessful; direct referral can be appropriate under the service specification. Language, attention, anxiety, learning disability, fatigue and unfamiliarity may all affect performance. Explain and practise the task, adapt communication and record the reason for incompletion. Repeating indefinitely can delay diagnosis in the children who most need an accessible assessment.

Refractive error affects how light is focused on the retina. Myopia blurs distance vision; hyperopia imposes an accommodation demand that young children may partly overcome; astigmatism produces orientation-dependent blur. Anisometropia means different refractive errors between the eyes. A child can accommodate enough to appear to see a target while still having a clinically important refractive or binocular problem. Cycloplegic refraction temporarily relaxes accommodation and helps the examiner measure the underlying error without relying entirely on the child's responses.

Management depends on acuity, age, refractive findings, alignment and ocular health together. Glasses may provide the first stage of treatment and can improve acuity over time. Persistent amblyopia may need additional orthoptic treatment after the image has been optimised. An accommodative esotropia may improve with appropriate hyperopic correction, while other squints need a different plan. Prescription thresholds from adult practice should not be applied mechanically to every young child. Follow-up confirms whether the correction is worn, fits properly and produces the intended visual benefit.

Newborn and infant eye checks have a different purpose and timetable. NIPE is offered within 72 hours after birth and again at six to eight weeks, with eye screening directed primarily at congenital cataract. A normal early red reflex does not exclude refractive error, later-developing disease or amblyopia. Family concerns at any age deserve assessment on their own merits. NHS sight tests are available without charge for children under 16 and young people under 19 in full-time education; inability to read is not a reason to refuse an examination.