In response to Sean Rai-Roche’s article ‘Weak data leaves public in the dark over screen time’ (June 21) I would like to pick up a couple of points that are worth noting.
The article draws on a number of sources. Those sources are likely to have considered the available evidence from different perspectives. The College’s comments were on the evidence about the impact of screen use on vision and eye health. As noted in the article, the College is supportive of guidance that encourages children and young people to spend more time outdoors every day – for both eye health and general health. The note of caution on the guidelines offered by the WHO, NHS and RCPCH was in relation to the weight given to the impact of screen time specifically on eye health and vision, and was not intended to diminish the value of these recommendations from a general health perspective.
The article also provides an opportunity to acknowledge the important reality that there are many aspects of clinical practice across health areas for which evidence is lacking or weak / low quality. The challenge for clinicians is to determine how to advise patients in respect of these areas. Clinical consensus is a valid source of information, but attention must be paid to the way the consensus has been developed, and also to the reality that even the most rigorous clinical consensus exercises will only produce ‘evidence’ that is low on the overall hierarchy of evidence.
The competing issue is that captured in the old adage ‘the absence of evidence is not evidence of absence’ – the fact that we do not have evidence that something causes something else, or that a treatment or intervention is effective, does not necessarily mean that the evidence to support a causal link or treatment’s efficacy will not emerge. This is why systematic reviews are such a vital tool in determining when we know enough to be confident about a given association or intervention. One or two studies, even good quality ones, are unlikely to produce the evidence to give us confidence that an unanswered question is now answered, or that we can now be certain about an area of clinical uncertainty.
Perhaps few will be surprised that a director of research is advocating for more research – turkeys advocating for vegan Christmas – but the reality is that if a careful review of the evidence available suggests there are gaps, or that the evidence available is limited or of low quality, then more research is the solution. While we wait for that research to be completed (and it may be several studies over a number of years that are needed) then high quality clinical consensus exercises can provide important guidance on how to act while the uncertainty remains.
Mike Bowen
Director of research
The College of Optometrists