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RANZCO myopia position paper: Why outdoor time is essential

RANZCO has published a new position paper on myopia, advocating for a more nuanced public health policy that incorporates increased outdoor time to limit progression in children while protecting against UV light exposure.

The college board approved its RANZCO Position Statement: Progressive Myopia in Childhood on 25 May to coincide with Myopia Awareness Week (23-28 May). It works to provide guidance to RANZCO Fellows and other health professionals regarding best practices for diagnosis and treatment.

Noting that by 2050 10% of the global population is predicted to have high myopia – defined as myopia of ≥ -6.0 D and axial length of ≥ 26.0 mm or more in either eye – RANZCO acknowledged the impact of various interventions such as defocus spectacles and contact lenses, as well as orthokeratology and atropine.

Overall, it said only relatively short-term outcomes of treatment exist and there is little data concerning the value of additive treatments, such as combining environmental, optical, and pharmacological interventions. However, it did highlight various studies such as ATOM2 (out to five years) and LAMP (out to three years) in atropine, and five-year data on dual focus spectacles, and six-year data on novel design contact lenses.

In its position paper, RANZCO paid particular attention to the importance of outdoor light exposure.

It suggested the adoption of a more nuanced public policy for sunlight exposure that aims to optimise UV exposure to reduce skin malignancy, but not to the level that results in vitamin D deficiency. And, importantly, maintains exposure to sufficient high-intensity sunlight to minimise myopia progression.

“In recommending children increase outdoor time, a child’s subsequent risk of skin cancer and UV-related eye diseases, including periorbital skin cancers, ocular surface tumours including limbal squamous cell carcinomas, pterygium, cortical cataract and increased risk of age-related macular degeneration, must be balanced with their risk of myopia,” the college stated.

“By increasing the exposure of the paediatric eye to an increased lux of visible light and limiting a child’s exposure to UV radiation, it should be possible to limit both UV-related eye diseases and myopia.”

What the studies say 

The paper noted a meta-analysis by Ho CL et al assessing the dose-response relationship between outdoor exposure and myopia indicators that found more than 120 minutes of daily outdoor light exposure decreased myopia incidence by 50%, spherical equivalent refraction by 32.9% and axial elongation by 24.9% for Asian children aged 4–14 years.

Furthermore, spending less than 40 mins outdoors per day was associated with more rapid axial length progression.

“Hence, it is recommended that at least two to three hours of outdoor exposure per day should be encouraged during childhood,” RANZCO stated.

“Karouta and Ashby noted that UV exposure does not underlie the ability of bright light to retard the development of deprivation-myopia or the ability of bright light to maintain normal untreated eyes in a hyperopic state. Instead, their data suggest that the ability of light to retard the development of deprivation myopia is driven by intensity-dependent increases in retinal dopamine release.”

RANZCO also pointed to a Singaporean study that used child mannequin heads with sunglasses and a hat for UV protection to assess the effect of different outdoor environments on the lux of light reaching the eye.

Even with UV protection, the light levels were still 11 to 43 times higher than indoors.

“This light level was considered sufficient for myopia control if outdoor exposure was undertaken for at least two hours per day,” the paper added.

A collaborative approach to myopia management

RANZCO also stated that with improved accessibility of monitoring tools and the advent of intervention strategies for myopia progression in children, practitioners can now take a more active role.

“Co-management, collaborating with optometrists and orthoptists for ongoing care is considered the best-practice approach. However, expert consensus highlights the importance of involving an ophthalmologist,” the college stated.

RANZCO stressed that developing myopia is not confined to children, and it is possible for adults to develop it later in life.

“The minimisation strategies, signs and steps to management remain the same. It is more common in families with myopia, but with increasing prevalence we all can be affected and need to be aware,” the paper said.

“Glasses are the most common tool for managing myopia, allowing images in the distance to become focused. Drops can be prescribed to slow myopia progression and reduce the risk of developing severe myopia and its blinding complications later in life.

“In adulthood myopia can be managed using contact lenses, refractive laser surgery, implantable contact lenses and lens exchange surgery, especially for people who have distortions from their glasses or want to undertake activities not conducive to wearing glasses.”

Finally, RANZCO stated that any treatment initiated in childhood aims to reduce the burden and incidence of high myopia and the associated development of pathological myopia.

“Patients and their families must understand that any attempt to prevent or slow myopia is ‘playing a long game’, and the potential benefits are largely some decades in the future.”

More reading

Change agents: educating parents about myopia

Atropine for myopia control: science and practice

Axial length matters in myopia management

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