“It’s important to identify a child before they even become myopic”
Professor Kathryn Saunders and Dr Sara McCullough of Ulster University discuss a longitudinal study into the prevalence and risk factors of myopia in children in the UK
21 August 2021
OT spoke to Professor Kathryn Saunders, subject lead for Optometry & Vision Science at Ulster University, and Dr Sara McCullough, research associate in Optometry and Vision Science, about the study and the risk factors identified, and how the researchers are building on this with a new study into key environmental factors. OT also heard how optometrists can be bringing lifestyle advice into the conversation.
What is the NICER study? What did you set out to investigate?Professor Kathryn Saunders (KS), subject lead for Optometry & Vision Science at Ulster University: We started the NICER Study in 2006 with funding from the College of Optometrists. We wanted to look at what the prevalence of myopia was in childhood in the UK because we were receiving reports from East Asia and other parts of the world that there was a rising prevalence, and we didn’t have any up-to-date contemporary data for modern children in the UK.
We went into schools and looked at around 400 children aged six and seven, and about 600 children aged 12 and 13. We looked at those two age groups because we wanted to be able to compare our prevalence with other studies from around the world, and so used the same robust methodologies. We received further funding from the College and support from Ulster University to follow those children up at three years, six years, then nine years later. Some of the participants were around 20–22 years old when we finished.
Key findings: the NICER study
The NICER study is the largest longitudinal research to be undertaken in the UK examining changes in children’s vision and cyclopegic refractive error over time. Key findings from the research included:
- The number of children with myopia in the UK has doubled over the last 50 years
- The development of myopia is most likely to occur in primary school, between six and 13 years of age
- Children with one myopic parent are almost three times more likely to be myopic by age 13 than a child without. A child with two parents who are myopic is over seven times more likely.
This allowed us to see how eye growth happens in a typical group of children in the UK; following a representative sample of children who were hyperopic, emmetropic, myopic, to look at their eye growth. It meant we could see how useful some of the measurements that we had made the first time we saw them were in predicting what their future eye growth and vision status would be like.
Dr Sara McCullough (SM), research associate in Optometry and Vision Science at Ulster University: We took measurements of their refractive error and assessed their ocular biometry – taking measurements of the size and shape of their eyes. We looked at their body measurements; height and weight and we knew about their family history in terms of refractive error. We also looked at their lifestyle – how much time they spent reading or doing physical activities.
How are you expanding on this in NICER 2.0?KM: One of the reasons for NICER 2.0 was that there has been a lot of talk and concern amongst parents about the influence of digital devices and the time children were spending on them, and whether this was the reason we had found that myopia was on the increase.
Exploring the impact of sleep
Because there is evidence that spending more time doing near activities could promote progression of myopia, we wondered if we looked at 2018 in comparison to 2006, whether there would be an increase as perhaps those children who were more susceptible to the impact of using devices might show a difference in prevalence of myopia between the two cohorts. We haven’t got the outcomes from that data yet.
We now have access to quantitative measurements of time spent outdoors, light exposure, physical activity and near vision activity by using devices like Fitbits. There are devices called Actiwatches – a wrist worn device that measures light exposure and physical activity, so gives us an idea of sleep as well, and devices which can be attached to the spectacles and record what distance children are looking at and what light exposure they are getting.
We used apps on the children’s phones or tablets so we can record screen time in a subgroup of children involved in the study, and it is also important to continue with self-reporting methods of identifying environmental risk factors as well, because this is what has been used in the past, so you are comparing like-for-like.
It is much more challenging to get these quantitative measures, because getting a child to wear the glasses with a little device and making sure they are charged, is a bigger deal than asking them how many hours they spent watching TV or playing outside. But if we can get even small numbers of very carefully measured metrics, that will just add another piece to the puzzle, and I think that’s a really important aspect that hasn’t been looked at in the past.
How does the NICER research help to inform our understanding of myopia and approaches to myopia management?
We’ve developed a risk indicator using the data from the NICER study that pulls together all the information in terms of the metrics that optometrists can use to determine how at-risk a child is, and then stratifies them into the level of risk to be able to give the parents an indication as to how important it is to get their child outdoors and adhere to the lifestyle advice that they’ve been given. Dr Leslie Doyle has done a lot of the work in developing the risk assessment tool: PreMO Risk Indicator.
KS: It’s important to identify a child before they even become myopic. Because if you can push back myopia onset until you’re older, you have slower-growing eyes and you’ll progress less quickly. I think that’s something that probably hasn't quite got to practitioners yet.
What are some of the key risk factors the NICER study identified?SM: The strongest risk factors seem to be refractive error at an early age. From the NICER data we found that refractive error of less than +0.75D of spherical equivalent under cycloplegia at six to seven years of age is a significant risk factor for developing myopia by at least 16 years. But we also know that if you’ve got that number, you’re quite likely to become myopic by the age of nine or 10. So it’s a significant risk factor.
Another factor we looked at has been the axial length, again at six to seven, of over 23 millimetres. So the NICER study found that eyes of 23.19 mm or more in length were at significantly increased risk for developing myopia by 16 years of age.
The other factor is family history. A child with one myopic parent is six times more likely to become myopic by the age of 16 than someone who has no myopic parents. In the NICER study, children with two myopic parents were seven times more likely to be myopic at 12-13 years, compared to peers with no myopic parents.
KS: Using a combination of these metrics, children at greatest risk for becoming myopic before the age of 10 can be identified. They are children aged six to seven years with lower ser (< 0.19d), at least one myopic parent and longer axial lengths (≥ 23.19 mm).
How can optometrists discuss myopia with families, and how can lifestyle changes be brought into the conversation?KS: Once these measurements have been taken, you put them into the risk calculator, and it tells you what your risk score is. But whilst you can’t change the biometry of it, you can change your lifestyle.
Something that I think parents find a bit challenging is that they want to just say that the tablets and phones are bad, but we of course don’t want to put children off studying, which is still a near vision activity. From the Sydney Myopia Study, we can say to parents: “It’s not that we don’t want the child to do lots of studying – they can do all that near vision activity. But you need to have a balance.”
I try to talk about having a healthy visual diet and the importance of balancing what your eyes are doing as you would with any part of your body. The includes the idea of healthy sleep and activity patterns.
We can also share a growth chart for the eyes with parents. What’s really important is to plot how their eye growth changes over time – we want to see steady growth along the centile. Our research has shown that, if you started on the 50th centile for example, and are average at six or seven years old, but at your next visit you crossed into the next centile, that’s a really worrying sign for future myopia.
Is there any key thing optometrists can be doing to be proactive in monitoring for myopia?SM: One of the things that we feel needs to come into more normal clinical practice is measurement of axial length. If you’re trying to monitor children who have eyes that are growing too large, and the reason that we’re wanting to slow the progression is because having too big an eye is more likely to have pathology, then you need to have something that measures axial length. There’s probably going to be a shift in the way optometrists practice in that respect in the next 10 years.
KS: There are some instruments out there and new instruments that are coming online which are specifically designed for practitioners who want to do myopia management. There are going to be more of those kits available over the coming years and I imagine that the prices will come down.
Is it becoming more of a necessity to have devices to measure axial length?
KS: If I was doing myopia management, I would want one because I’d want to know that I had the right measurement tool to see if the myopia management treatment was working. Having said that, it is not customary practice at the moment for everyone to have an axial biometer and there are other methods – we have some calculations available in the PreMo tool that allow you to take the measurements that you do have and estimate your axial length. I think a cycloplegic autorefraction is a valuable measurement to have which is available to almost all optometrists, so that you have a baseline measurement which is more repeatable than a general retinoscopy or subjective refraction.
SM: At this time where practices don’t have axial biometers, I would still encourage people to start looking at myopia management and encouraging that practice. I think in the long term, to do that appropriately and to be able to know whether your treatments are working or not, then it needs to be something that's goes from just a nice-to-have to a must-have.