Reply to letter to the Editor: Expert Opinion on Best Practice Guidelines and Competency Framework for Visual Screening in Children

Dear Editor,

I thank the interest that T. Garrety et al. have shown in the article “Expert opinion on best practice guidelines and competency framework for visual screening in children” and for their valuable and interesting comments.

The aim of this study was to describe experts’ perception of best-practice guidelines and competency framework for visual screening in children. This study uses qualitative data and shows individual/group conceptualization. The use of evidence from qualitative studies has traditionally been a fundamental source of knowledge in the clinical and social sciences.1

The panel of experts had more than 10 years of working experience in visual screening. Some of them have been working in the national vision plan, defining guidelines, strategies, referral criteria, and tests for visual screening. Others have been participating in visual screenings all over the country and also participated in international groups of discussion about visual screening.

The conclusions of the study highlight the need for reliable screening methods and it is also stated that screening tests need further clarifications to allow determination of diagnostic test accuracy. To my knowledge there is no single test that succeeds in fulfilling that role.

The results of the study also compel the discussion about a framework on core competencies, which can contribute to better screening programs development. Certainly one must realize that for a simple cover test, usually several years of experience are required.

Preventable visual loss caused by amblyopia (0.3%–4%) and its risk factors such as strabismus (2.1%–4.6%) and uncorrected refractive errors (5%–7.7%) represent an important public health problem.2–10 Thus the primary justification for preschool vision screening is the detection of amblyopia, or amblyogenic refractive, strabismic, or ocular disease conditions.4,11 Some authors support and advocate that visual screening is effective in detecting visual and ocular disorders and that functional complications of vision anomalies can be reduced or eliminated if these diseases were treated preventively.4,12 Strabismic amblyopia usually presents with a visible squint, but refractive amblyopia or a small angle strabismus may not be detected until it is too late for treatment to be effective.13

However, visual screening programs are a specific challenge especially because we do not have access to data about their effectiveness. It is well known that visual screening programmes vary in terms of their application in many countries all throughout Europe. Therefore, it is necessary to open the discussion about and reflect on this matter: Are the screening programmes appropriate for providing a correct and timely treatment? Are the screening programmes adequate for reducing health inequities and cost for health care systems?

A Cochrane review on screening specifically for amblyopia (1947 to 2008) concludes that “the lack of data from randomized controlled trials makes it difficult to analyze the impact of screening programs on the prevalence of amblyopia. The absence of such evidence cannot be taken to mean that vision screening is not beneficial; simply that this intervention has not yet been tested in robust studies.”14 The conclusions of this review are of special importance because the authors state that it is necessary to have consensual definitions, normative data, and appropriate tests. Quantification of the consequences of living with untreated amblyopia is still in need of a more exact assessment.

Nonetheless, on average, screening before 3 years of age has been associated with a lower prevalence of amblyopia after treatment.13,15 Children treated for amblyopia are 4 times more likely to remain amblyopic if they were screened at 3 years of age, only than if they were screened repeatedly between 8 months and 3 years of age.15 There is no contradiction in proposing more than one screening age–they are platforms for successive filtering. In this example patients had already been screened at an earlier age.

Children with a moderate acuity loss of 6/18 or worse showed a clear-cut response to treatment, which itself arguably justifies screening to identify and treat these children.13 On the other hand, more research is needed, therefore, to explore which tests could be sufficiently accurate to be part of a visual screening programme for children.

We also developed a recent study in Portugal on a sample including 672 children of school age (7.69 ± 1.19) and found out that low visual acuity (11.3%) and uncorrected refractive error (10.3%) affected a significant proportion of school age children. These anomalies influenced reading performance at school with a higher number of errors and a lower precision in reading when comparing children between 4 school grades. Children with hyperopia and astigmatism presented more errors and a lower precision in reading than children without a significant refractive error.

Overall, the analysis contained in T. Garrety et al. letter to the editor reflects on the nature of screening itself and can be accepted only as doubting the use of any screening policy, since adopting too simple an approach means losing efficiency, both in terms of specificity and sensitivity. It is important to make informed decisions about screening:

• Why do children below the age of 4 years have to wait to get an early detection and treatment?

• If the proportion of false positives from a screening programme is high, shouldn’t we try to develop more accurate tests, referral criteria, and screener competencies?

• When the parents find out that the child already had the problem and that they could not identify it earlier than 4 years of age, won’t that also raise parental anxiety and feelings of guilt?

We feel that the results previously presented and the present results of reading performance might help in the design of future studies and were important especially for raising discussion about this subject. Further evidence-based studies are necessary to make a more informed decision about the appropriate age for implementing visual screening.

We thank once more the comments, which were very important in prompting this debate.

Declaration of Interest

The author reports no conflict of interest. The author alone is responsible for the content and writing of this article.