Just before Christmas 2020 I posted a blog about the increasing prevalence of myopia and the long-term implications of this worrying situation. I thought that it was about time I shared a few more thoughts on this with you as most of us, in particular children and young people, are currently spending large amounts of time indoors staring at a device of some sort.
Myopia is really a big issue in eyecare! Here are a few interesting facts:
93% of Taiwanese medical students are myopic.
The prevalence of myopia in UK has more than doubled in last 50 years.
50-53% of UK university students are myopic.
Why does myopia matter?
The simple fact is that there a significant health impact of high myopia (over -6.00 D) with an increased risk of retinal detachment, myopic macular degeneration, glaucoma, & other eye conditions. Interestingly there is no evidence of a safe threshold level of myopia for any of the known ocular diseases linked to myopia. In other words, we cannot say that you are safe from any of the ocular diseases associated with myopia if your prescription is -3.00 D but not at -4.00 D. One study has shown that slowing myopia by 1.00 D should reduce the likelihood of a patient developing myopic macular degeneration by 40% regardless of the level of myopia.
We have known for some time that myopia is multifactorial and that there are lifestyle approaches to myopia control. A study found that holding near tasks at a distance greater than 30 cm (some children have a habit of holding books and screens at very close distances), stopping near work after 30 minutes and spending school breaks outdoors reduces myopia prevalence & progression in compliant children. My friend and Optometric colleague Professor Bruce Evans simplified this as the “30:30 OUT rule”. Parents should think of this “balanced vision” in the same way as we think of a balanced diet. The effect of this lifestyle approach on myopia control is measurable but small and the contribution of screen time in myopic progression equivocal.
Myopia is a result of the eye being too long and Myopia control is all about slowing the growth of the eye (front to back) a measurement that we refer to as axial length. There are essentially three ways of doing this. These are the use of a drug called Atropine or the fitting of contact lenses or spectacles lenses specifically designed for the purpose of myopia control. Atropine is not licensed in the UK for myopia control and the side effects are pretty nasty. Myopia control with contact lenses works well but there are some limitations. Both the child and the parent must actually want to be fitted with contact lenses. Some children struggle with contact lens handling an d microbial keratitis (infection due to poor hygiene and lens cleaning) is a risk. My preferred option for myopia control is the use of spectacle lenses which are designed to both correct and treat myopia. As I mentioned in my earlier blog on myopia, we have been lucky enough to trial the Hoya MiyoSmart spectacle lens. This lens incorporates DIMS technology which is short for defocus incorporated multiple segments. Trials in Chinese children have shown that myopia progressed 52% more slowly in children wearing the MiyoSmart spectacle lens as opposed to a standard single vision spectacle lens. In addition, there was 62% less axial elongation (growth of the eye). There are some concerns and questions about the long-term effects of myopia control for example, is the treatment effect sustained or is there a rebound effect when treatment stops?
So, when should myopia control be considered?
Some authorities advocate that treatment should start when the myopia starts and others prefer to commence treatment when hypermetropia reduces. Remember that all babies are born hypermetropic which reduces with age as the eye grows. This growth should stop when the hypermetropia has disappeared but if the eye continues to grow, hey presto, myopia! Historically children became myopic in their early teens. However, children are now presenting with myopia at a much earlier age and early onset does indicate early treatment, especially if both parents have high myopia. As 90% of myopic patients are stable by age of 21 years this is the point at which treatment would be stopped and a standard single vision lens be dispensed.
So, what about myopia control in the time of COVID-19? An annual routine sight test of 123,500 children in China showed a significant myopic shift in 2020 for children aged 6 to 8 years. This has been attributed to home confinement during January to May 2020 owing to COVID-19.
The children from the practice that are wearing the MiyoSmart spectacle lens for myopia control are doing well and the lens has now become available to order outside of any trial. I will provide regular updates via the website but please get in touch if you have any questions.