Updated: May 3
Myopia (short or near sightedness) is a very common eye condition that occurs when light is focused in front of the retina inside the eye, meaning that distant objects appear blurred. There are two main types of myopia; axial and refractive. Axial myopia is very common and occurs when the eyeball grows too long / stretches, which can cause sight threatening damage to many of the internal structures of the eye later in life. This type of myopia primarily develops in childhood and the prevalence is getting much worse globally, including in the UK.
If you have seen a spectacle or contact lens prescription, Myopia is corrected using a minus (-) lens power. Anyone with >-0.50 D (Dioptres – the measure of focussing power) in their prescription is considered as having Myopia, anyone with a prescription above -6.00D is considered as having high Myopia. Any level of Myopia increases the risk of eye conditions, but those with high Myopia are at much greater risk. However, there are myopia management strategies available to slow down the progression of the condition.
Let's take a look at the causes, risk factors and increasing prevalence of the condition worldwide. There are genes that increase the risk of developing Myopia, but they don’t account for the huge increase in the numbers affected by the condition. It is clear that modern lifestyles are affecting childhood Myopia. Since the Covid-19 crisis began, for example, the increased use of screen time by younger people and the reduced amount of time spent outdoors has led to a clinically significant increase in the levels of myopia in children.
The American Academy of Ophthalmology produced a comprehensive list of all possible risk factors for Myopia. Theses include;
Near work or visual activity with a high focussing demand
Low levels of outdoor activity
Genetic factors – parental myopia
Younger age at diagnosis
In 2015 the WHO (World Health Organisation) reported that Myopia had reached epidemic proportions in many countries. The global prevalence of myopia is expected to increase from 27% of the world’s population in 2010 to 52% by 2050. Already, the cost of myopia to economies is huge - it is estimated that sight impairment and severe sight impairment in adults costs the UK economy around £37 billion per year! The human cost is, of course, the real issue and there is no doubt that the incidence of both myopia and, more worryingly, high myopia is on the rise.
You may ask, ‘Why does this increase in Myopia matter?’. The problem is the long term effects of having Myopia, in particular high Myopia. Myopia increases the risk of multiple eye conditions, including cataracts, glaucoma, retinal detachment, MMD (Myopic Macular Degeneration) and many more.
The chart below shows just how much more likely you are to develop some of these conditions if you have a higher degree of myopia.
One of the largest causes of new sight impairment and serious sight impairment registrations in Southeast Asia and Japan is Myopia related eye conditions. Currently, the prevalence of Myopia in the UK is around 33%, but it will increase to between 50 and 60% by 2050.
The World Council of Optometry (WCO) recently ratified a document suggesting Myopia should no longer simply be considered a refractive error, but should be classed as an eye disease and all children should be routinely screened for the condition.
Let's talk about the diagnosis of myopia. There are several tests that an eye care professional will need to carry out to diagnose childhood myopia and asses the risk of progression. These tests include:
Measure the refraction (the spectacle prescription) – usually using eye drops to relax the eye muscles from over working in younger children
Measure the curvature of the cornea (keratometry)
Ask questions about lifestyle, family history of myopia, ethnicity and more besides
Measure the length of the eyeball (axial length using optical biometry)
From here, it is possible to then build up a better understanding of when myopia did first develop or may first develop and perhaps get an understanding from scientific data what level of myopia the child may eventually have without treatment. The problem with only using the spectacle prescription to understand the myopia risk in a child is that the prescription does not always predict what the length of the eyeball will be. Therefore, the modern consensus is that measuring the axial length is the primary tool in myopia diagnosis and management.
Genetic Factors – it is well established that children with parents who are both myopic have a much higher likelihood of developing myopia themselves. However, this likelihood also increases depending on ethnicity too. East Asian children have the highest prevalence of myopia, followed by Hispanics, whilst Caucasians have the lowest childhood prevalence.
Although genetics increase the pre-disposition to myopia and myopia progression, they simply do not account for the current levels of myopia being witnessed globally, even in the Far East. This increasing prevalence of myopia has significantly been impacted by environmental and lifestyle factors. For example, a recent study from Hong Kong and Singapore showed that Covid had caused a significant increase in myopia (refraction and axial length) in children. The study concluded that outdoor time had decreased from an average of 1.27 hours per day to an average of 0.41 hours per day whilst at the same time, screen time had increased from an average of 2.45 hours per day to 6.89 hours per day. From this, it was easy to infer that a combination of less time outdoors and increased near work/screen time affected the levels of myopia beyond those perhaps expected due to the genetic pre-disposition. It is likely, however, that the impact of reduced outdoor time and increased near work was high in these children due to their genetic pre-disposition to myopia.
You’ll be happy to know that there is a lot that can be done to help slow down the rate and amount of progression of Myopia in children, reducing the long term risks to their vision. The main therapies include:
Specialist spectacle lenses
Specialist soft contact lenses
Specialist hard contact lenses worn overnight (Ortho-K)
To learn more about these therapies click here
If you're a parent whose child has been diagnosed with myopia, or if they are struggling with their distance vision, we hope you found MyopiaFocus helpful. Please join our community or sign our petition to get the government and NHS to recognise myopia as an ocular disease/serious ocular condition and fund myopia management for children.