Strabismus

Although there is no known primary intervention for the prevention of strabismus, for some forms, removal of risk factors (e.g., partial correction of hyperopia >4 dioptres in children without manifest strabismus and prevention of preterm birth) can prevent its development. Vision screening is therefore an important part of paediatric care, as children often do not complain of visual or eye problems when they are present. Screening for strabismus is generally recommended between the ages of 3 and 5 years, depending on local or national guidelines, and typically focuses on amblyopia, refractive errors, and strabismus. Specifically, the appropriate treatment of strabismus in childhood has been shown not only to improve vision and motor skills in childhood but also to prevent visual morbidity later in life.

UK screening programme

The UK National Screening Committee (NSC) recommends vision screening for children aged 4-5 years in an orthoptic-led screening service.[23]Gov.UK (National Screening Committee). Child screening programme: vision defects. Aug 2019 [internet publication]. https://view-health-screening-recommendations.service.gov.uk/vision-defects ​ Many disorders causing significant visual impairment, such as cataract, cerebral visual impairment, and retinopathy of prematurity, can be detected in infancy by a trained professional through the UK newborn and infant physical examination (NIPE) screening programme or by surveillance of high-risk populations.[24]Public Health England. Child vision screening. Apr 2019 [internet publication]. https://www.gov.uk/government/publications/child-vision-screening

US screening programme

The US Preventive Services Task Force (USPSTF) and American Academy of Ophthalmology (AAO) recommend vision screening at least once between the ages of 3 and 5 years, and they also endorse the use of photoscreening when needed.[1]US Preventive Services Task Force. Vision in children ages 6 months to 5 years: screening. Sep 2017 [internet publication]. https://www.uspreventiveservicestaskforce.org/Page/Document/UpdateSummaryFinal/vision-in-children-ages-6-months-to-5-years-screening [25]Hutchinson AK, Morse CL, Hercinovic A, et al. Pediatric eye evaluations preferred practice pattern. Ophthalmology. 2023 Mar;130(3):P222-70. https://www.doi.org/10.1016/j.ophtha.2022.10.030 http://www.ncbi.nlm.nih.gov/pubmed/36543602?tool=bestpractice.com [26]American Academy of Ophthalmology. Vision Screening for Infants and Children - 2022. Oct 2022 [internet publication]. https://www.aao.org/education/clinical-statement/vision-screening-infants-children-2022 ​ To detect strabismus, children should undergo eye examination in the paediatrician's office, including an evaluation of ocular alignment. The recommended tests are:

• Cross-cover test (alternate cover test) while child fixates a target at a distance of 3 m

• Random dot E stereo test at 40-cm distance

• Simultaneous red reflex test from 2 to 3 feet away (Brückner and Hirschberg tests).

Children should then be referred for an eye evaluation by an ophthalmologist experienced in the care of children if they meet one or more of the following criteria:

• Any eye movement on the cross-cover test (alternate cover test)

• Fewer than 4 correct responses out of 6 on the Random dot E stereo test

• Any asymmetry of pupil colour, size, or brightness on Brückner testing.

Childhood screening tests and recommendations by age

In addition, the following screening tests can be performed by paediatricians or primary care providers during routine health maintenance visits from birth.[25]Hutchinson AK, Morse CL, Hercinovic A, et al. Pediatric eye evaluations preferred practice pattern. Ophthalmology. 2023 Mar;130(3):P222-70. https://www.doi.org/10.1016/j.ophtha.2022.10.030 http://www.ncbi.nlm.nih.gov/pubmed/36543602?tool=bestpractice.com

Newborn to 3 months of age:

• Red reflex test with a direct ophthalmoscope. Refer if absent, white, dull, opacified, or asymmetric.

• External inspection of the eyes to assess for any structural abnormalities (penlight examination is sufficient). Refer structural abnormalities (e.g., ptosis).

• Pupillary examination. Refer if irregular shape, unequal size, and poor or unequal reaction to light.

• In a co-operative infant ≥3 months:

  • Fix and follow. Refer if failure to fix and follow.

  • Corneal light reflex to check for a symmetrical response in both eyes. Refer if asymmetric or displaced.

6 months to 3 years of age:

• Repeat the tests for the previous age group.

• Consider instrument-based screening for co-operative infants ≥6 months old (e.g., photoscreening and autorefraction), especially for the young and those with developmental delays. This can detect media opacities, strabismus, or concerning refractive errors. However, subjective visual acuity testing is preferred when possible. Refer children with strong myopia, hyperopia, astigmatism, anisometropia, media opacities (>1 mm), and manifest strabismus.

3-4 years of age:

• Repeat the tests for the previous age group.

• Cover/uncover test to assess for re-fixation movements in the fellow eye. Refer if re-fixation is present.

• Distance visual acuity testing, independently for each eye. Visual acuity of 20/50 or worse in either eye, or a ≥2-line difference between the two eyes, should be referred.

4-5 years of age, then every 1-2 years:

• Repeat the tests for the previous age group.

• Distance visual acuity testing, independently for each eye. Visual acuity of 20/40 or worse in either eye, or a ≥2-line difference between the two eyes, should be referred.

• Practice can become more sporadic in older childhood and relies on symptom reporting.

If screening is inconclusive or unsatisfactory at any point, retest the child within 6 months; if this is not possible or testing remains inconclusive, refer for a comprehensive eye evaluation.[25]Hutchinson AK, Morse CL, Hercinovic A, et al. Pediatric eye evaluations preferred practice pattern. Ophthalmology. 2023 Mar;130(3):P222-70. https://www.doi.org/10.1016/j.ophtha.2022.10.030 http://www.ncbi.nlm.nih.gov/pubmed/36543602?tool=bestpractice.com [27]American Academy of Ophthalmology. Referral of persons with possible eye diseases or injury - 2014. Apr 2014 [internet publication].​ https://www.aao.org/education/clinical-statement/guidelines-appropriate-referral-of-persons-with-po ​​​​ Children with developmental delay may be unable to co-operate with visual acuity testing in a paediatrician’s office or during school or community-based vision screenings. If they cannot be screened, they should be referred to a paediatric ophthalmologist, orthoptist, or optometrist for a complete evaluation.