In this blog, Salma Ahmad and Catherine Suttle address some questions about whether long-sighted children need to wear glasses, with the help of recent Cochrane evidence.
Harry Potter and Spongebob Squarepants do not seem to have much in common, but they are both young and wear glasses. Harry’s seem to be worn full time, but for Spongebob only when jellyfishing. Do they really need them? What would happen if they discarded them? Would their vision suffer, would their quality of life be affected? Are more jellyfish caught with than without glasses?
Despite their imaginary nature, these are real questions, serious ones. Do children benefit from wearing glasses? Are vision and wellbeing better in children who wear their glasses than in those who do not? Perhaps there is little benefit or even harms (for example, glasses cost money, and once they are bought the child needs to be encouraged to wear them; this cost and effort may be difficult for many parents or carers). These questions have been addressed in several ways by researchers looking at the effect of wearing glasses on outcomes such as visual acuity (clearness of vision) and squint (or eye turn, also termed strabismus).
Long-sight in children
The long-sighted (hyperopic) eye focuses light towards a point too far, behind the eye. A long-sighted child can focus the light, without help from glasses, back onto the retina to allow clear vision. Due to a link between focusing and eye position (when we look at close objects our eyes turn in), young children who are long-sighted are at risk of an eye turning in toward their nose (a squint).
If the child is unable to focus the light entirely, the child may develop ‘lazy eye’, otherwise known as amblyopia. In this case, the visual system undergoes abnormal development such that vision is reduced in one or (rarely) both eyes and cannot be easily improved with glasses. This condition occurs in about 2% of people globally (Fu et al., 2019), and we are susceptible to it only in childhood, so it is very important to understand the effectiveness of glasses in the correction of vision and squint in children.
New Cochrane evidence on long-sighted children wearing glasses to prevent a squint
This issue was addressed recently by an updated Cochrane Review comparing wearing glasses with not wearing them for preventing a squint in long-sighted children (published April 2020). They looked for randomized controlled trials to find out whether glasses prevented a squint in these children, but they also included results on other outcomes.
The review authors searched for studies published from January 1946 to 4th December 2018 and found four eligible studies. Three of these were conducted in the UK, and one was conducted in the US.
So, what did they find?
The combined results of the four studies showed that the risk of developing a squint may be reduced by about one third in long-sighted children up to three years of age wearing glasses, compared to those without glasses. However, one of the studies found there may be little or no difference between those with and without glasses at the follow-up after three years, suggesting that if there is a benefit, it may not be sustained. The same study looked at other outcomes, including amblyopia and found there may be little or no difference between the two groups, but the evidence is very uncertain.
Overall, the studies did not find that children wearing glasses could see better than those without glasses, probably because of their high ability to focus (mentioned above).
Another important outcome reported in the review was ‘emmetropization’, a normal developmental process in which refractive error, such as long-sightedness, reduces over the first few years of life. We expect babies to be long-sighted and for this to reduce as they go through their early years. Again, this is normal and expected. If we ‘correct’ this (creating an abnormal situation), it is possible that the developmental process will be affected, and the long-sightedness may not reduce as it should. This important possibility was also investigated as part of the review; three studies reported on this outcome, but their results were not in agreement.
A risky business…
Overall, critical appraisal of the four included studies showed that none of them provided highly reliable research results. The studies were at ‘high risk of bias’, meaning that their methods did not include several measures that are designed to reduce biased results. For example, none of the four studies included ‘masking’ of the research team; if the researchers are aware which child is in which group in the trial, they may anticipate specific findings leading to biased results.
The bottom line: do long-sighted children need glasses?
The review authors suggest that further research is required, with better study methods before the effects of wearing glasses in long-sighted children and their risk of developing a squint can be estimated with any certainty.
In the absence of clear evidence, discussions between parents or carers of long-sighted children and their eye care provider may include several issues related to the need for, and the likely benefits of, wearing glasses. For example, is the child’s vision with and without glasses normal for their age? Is there a squint with or without glasses? If vision is normal and there is no squint without glasses, what is the likely benefit of wearing them? Patient-centred, informed decisions can then be made based on the best available evidence.
Join in the conversation on Twitter with @CochraneUK, @CochraneEyes #eehealthchoices or leave a comment on the blog. Please note, we cannot give medical advice and we will not publish comments that link to commercial sites or appear to endorse commercial products.
Salma Ahmad and Catherine Suttle have nothing to disclose.