UKNSC consultation on childhood vision screening

The evidence review is incomplete. The NSC defines visual defects as including “amblyopia, refractive error and strabismus”¹ but the review only focuses on amblyopia.

Text/issue to which comments relate: “The purpose of this document is to review the evidence on childhood screening for reduced vision”.

It is not clear what the evidence review set out to evaluate. The opening line of the executive summary implies it will evaluate the evidence for “screening for reduced vision”. The NSC policy mentions screening for “vision defects” which is defined as “including amblyopia, refractive error and strabismus”

If the NSC’s objective with the review was to evaluate “the evidence on childhood screening for reduced vision” where “vision defects include amblyopia, refractive error and strabismus” then it is incomplete.

Text/issue to which comments relate: “Currently, the UK NSC recommends vision screening for children aged 4 to 5 years in an orthoptic led screening service”

A policy based upon competencies rather than professional boundaries would be supported by the evidence, reflect developments in the general NHS and public health workforce and potentially improve programme delivery without presenting any clear risk to the quality or efficiency of screening. Profession-based service descriptors are inflexible and out of step with developments across the healthcare where competence-based service definitions are now the norm. We believe a competency-based policy would be easier to implement across the UK without any negative impact on outcomes.

We recommend changing the policy to “all children should be screened for reduced vision between 4 and 5 years of age, with testing undertaken and led by competent professionals”.

Text/issue to which comments relate: “Although amblyopia is the main target disorder for the screening programme, any other disorder, such as functionally significant refractive error (error which is sufficiently severe to negatively impact visual development) would be detected through the current UK NSC programme which detects all-cause reduced acuity because of the detection of the resultant amblyopia.”

The decision to exclude causes of reduced vision other than amblyopia results from the assumption that refractive error alone cannot be considered a visual impairment or sufficiently severe a cause of reduced vision to merit intervention unless it is associated with amblyopia.

Assuming that refractive error cannot be considered a source of reduced vision unless it is associated with amblyopia is at odds with internationally accepted definitions of visual impairment. The World Health Organisation amended its definition of visual impairment from a classification based upon “best corrected visual acuity” (meaning how clearly one can see wearing corrective lenses)  to one using “presenting visual acuity” (how well someone can see given how they currently live, be that with or without corrective lenses). 

The WHO case for changing the definition noted that “Many recent studies have shown that the use of “best corrected” vision overlooks a large proportion of persons with visual impairment, including blindness, due to uncorrected refractive error, a common occurrence in many parts of the world. Uncorrected refractive error is now considered to be a major cause of visual impairment and estimations are under way to calculate the loss in terms of DALYs (disability-adjusted life years) resulting from this cause. The correction of refractive error is a cost effective intervention and is one of the priorities under the disease control component of the Global Initiative for the
Elimination of Avoidable Blindness (VISION 2020, the Right to Sight)”².

Under this definition, refractive error can be a cause of visual impairment if it is not diagnosed or corrected. Further more, the 2005 study by Robaei et al found that uncorrected refractive error was the biggest cause of reduced vision within a large population-based sample of children with amblyopia the next most common cause3. That a significant proportion of children who fail screening are likely to need corrective lenses due to refractive error is demonstrated by other studies^4,5,6.

Text/Issue to which comments relate: “Balance between the benefit gained by individuals from the screening programme and any harms, for example from over diagnosis, overtreatment, false positives, false reassurance, uncertain findings and complications.” 

A recent publication⁶ profiling those who passed or failed the UK School Vision Screening Protocol found that the majority of those who had a visual acuity measurement of 0.2logMAR or poorer in either eye (ie a level that constitutes a fail in the vision screening protocol) (51.9%) were false positives and did not demonstrate any need for clinical intervention on further examination. Conversely, a proportion of children (7.8%) with acuity of a level good enough to pass the screening protocol had strabismus and/or significant uncorrected refractive error and were given false reassurance. Previous reports have shown visual acuity measures in children to be a poor method of reliably detecting significant refractive error particularly hyperopia and astigmatism the most common causes of reduced vision in children.^7,8

1. https://legacyscreening.phe.org.uk/vision-child

2. https://www.who.int/news-room/fact-sheets/detail/blindness-and-visual-impairment

3. Robaei,D et al (2005) Visual Acuity and the Causes of Visual Loss in a Population-Based Sample of 6-Year-Old Australian Children, Ophthalmology, Volume 112, Issue 7, July 2005, Pages 1275-1282,  

4. Donaldson LA, Karas MP, Charles AE, Adams GG, Paediatric community vision screening with combined optometric and orthoptic care: a 64‐month review. Ophthalmic and Physiological Optics, 22: 26-31.

5. Newman DK, Hitchcock A, McCarthy H, et al Preschool vision screening: outcome of children referred to the hospital eye service. British Journal of Ophthalmology 1996;80:1077-1082. 

6. McCullough & Saunders (2019). Visual Profile of Children who Passed or Failed the UK School Vision Screening Protocol. British and Irish Orthoptic Journal, 15(1):36-46. 

7. Leone JD, Mitchell P, Morgan IG, Kifley A, Rose KA. (2010). Use of visual acuity to screen for significant refractive errors in adolescents: is it reliable? Arch Ophthalm, 128(7):894-9.

8. O'Donoghue, L, Rudnicka , AR, McClelland, JF, Logan, NS and Saunders, KJ (2012) Visual acuity measures do not reliably detect childhood refractive error - an epidemiological study. Plos One, 7(3):e34441 

Submitted: June 2019