06 Aug Public Health approaches to Myopia prevention and control – Part 1
The management of myopia is typically practitioner-led. Currently, the standard of care is to provide single-vision spectacle or contact lenses to eliminate the blurred vision symptoms, which are characteristic of myopia. Symptom-based management does little to address the underlying cause of myopia development or progression, nor does it affect the risks of eye disease development as a consequence of the excessive axial elongation caused by progressive myopia. This approach to clinical care is problematic from a population health perspective for three key reasons.
As Covid-19 is now painfully demonstrating, public health approaches to disease management are motivated by the risk of;
(i) large scale human death, disability and/or quality of life impact
(ii) healthcare service incapacitation
(iii) global economic disruption
Myopia is an established risk factor (second only to age) for the development of glaucoma, cataract and retinal detachment. Also, it is the primary risk factor in myopic macular degeneration. Even in countries where the prevalence is low relative to Asia, myopia is a leading cause of vision impairment. It includes a substantial proportion of the 116 million cases of moderate to severe vision impairment and 7 million cases of blindness due to uncorrected refractive error.
Myopic macular degeneration already accounts for an additional 10 million people with vision impairment, including 3.3 million blind despite refractive correction (almost double the numbers affected by glaucoma), and it is expected to grow six-fold by 2050. As a leading cause of vision impairment and blindness worldwide, myopia is undoubtedly a source of disability and quality of life loss. The economic costs are already huge, estimated at more than $250 billion per annum and growing. With 2 billion myopes currently (which is projected to reach 5 billion by 2050 as per Figure 1), the threat to eye care service sustainability is also very real. Myopia, therefore, meets all the criteria necessary to justify a global public health response, but this has yet to be politically prioritized in any meaningful way.
Figure 1: The Myopia Map: A global epidemic
The public health priorities in dealing with myopia are two-fold: (i) to prevent myopia onset where possible; and (ii) to mitigate the risk of ocular diseases such as retinal detachment and myopic macular degeneration and associated vision loss in those who become myopic. Public health strategies can be practitioner-led, involving health promotion activities provided to those attending primary care settings, or population-based where the entire population is targeted.
The primary care and population health approaches should, however, be complementary. Complete prevention or delayed onset (later onset is associated with slower progression) would be ideal. Among children who have already become myopic, altering the rate of progression can still reduce the lifetime risk of progression to high myopia and disease development. Eye health practitioners can primarily contribute to the latter by implementing a personalized risk-based management approach for the treatment of individuals with progressive nearsightedness.
The risk-based approach involves prescribing individualized, evidence-based treatments and behavioural modifications that slow or prevent continued progression. This form of clinical care targets the intrinsic physiology of eye growth by modifying optical defocus, altering growth signalling or motivating behaviour change to reduce exposure to known risk factors. These practitioner-led strategies provide additional choices to those at risk, which may or may not be adopted as they can involve additional cost or inconvenience and because parental awareness of the risks of myopia is low.
Among children who have already become myopic, altering the rate of progression can still reduce the lifetime risk of progression to high myopia and disease development.
Odds ratios can be a little difficult to interpret and integrate into our discussions with patients when recommending myopia control. A patient might ask “What does ten times higher risk actually mean?”. Some clarity has been provided by researchers in the Netherlands who evaluated the prevalence of vision impairment in relation to axial length. The prevalence of vision impairment by age 75 was seen to increase substantially with increasing eye size.
Among people with the longest eyeballs (over 30mm), vision impairment was almost universal, with 90% of the population affected (see Figure 2). Among people with axial length between 26-30mm, around one in every four suffer vision impairment by age 75, with those in the 28-30mm range developing vision impairment at a younger age typically compared to those in the 26-28mm range. The message is simple and clear: slowing down the abnormal growth of the eye which is characteristic of progressive myopia is hugely important for reducing the risk of vision impairment.
Figure 2: Moving to a risk-based management approach to myopia, offering active care management options and promoting better lifestyle habits.
In relation to myopia prevention, a more conventional public health approach is necessary, comprising community initiatives such as health promotion, health policy and systems’ reform to alter societal behaviour and thereby prevent myopia onset. Enhanced public health screening for myopia would also be useful in identifying those at risk (pre-myopes) and initiating earlier intervention for those already affected.
In Ireland, for example, school vision screening occurs at age 5, which is too early for most myopes. Public health approaches, at least initially, target exposure to extrinsic environmental and lifestyle factors that influence the intrinsic mechanisms of eye growth. There is strong evidence that time spent outdoors impacts the risk of myopia development.
Other factors, such as educational achievement and prolonged and continuous near work, also appear to be involved. Proliferation in the use of electronic devices may also contribute to myopia risk in two ways, first as a new form of extended near work, and second, as a barrier to children spending their leisure time outdoors (Figure 3). These risk factors represent the target for behaviour change through public health intervention. Measures such as modifying classroom design to allow more light and an extended field of view, increasing school break time outdoors and building awareness through public health campaigns are examples of interventions that have been implemented in parts of Asia where the myopia epidemic is long-established.
Figure 3: Smartphone dependency may represent a new risk for myopia development
Hong Kong, Taiwan, Singapore and China have all implemented public health interventions, some of which have proved moderately successful in impacting short term indicators such as myopia prevalence, incidence and progression rate. None of these public health strategies have been adopted outside of Asia, however, despite growing awareness of the socio-economic and health impact associated with myopia.
In Part 2 of this blog, we examined what form of public health approach might have the greatest potential for success both in and outside of Asia. Subscribe below to be notified once the second part is published.
James Loughman is the Clinical Research Director for Ocuco Ltd. An Optometrist with more than 20 years of clinical, academic, research and management experience. James is also presently the Director of the Centre for Eye Research Ireland, a research facility based in Technological University Dublin, the same university where he received his PhD in 1997. James oversees a portfolio of research including technology development and big data analytics projects alongside various clinical trials for the control of myopia, glaucoma and other blinding conditions.