Myopic progression is complex in its origins and there have been numerous studies performed in this area. Myopia prevalence in school-aged children is as high as 90% in South East Asian countries. In Australia, it is predicted to approach 50% by 2050. There have been significant scientific advances in the past decade that have given better insight into what causes myopia to progress. Genetics and environment play significant roles. More specifically, it is understood that peripheral hyperopia (long-sightedness) in myopic eyes is a driving force for myopic progression. The eye elongates as a result of the peripheral hyperopic defocus which in turn causes an increase in the degree of myopia.
Myopia control does not reverse the amount of myopia that is present. It aims at minimising the total amount of growth after initiating treatment so that we limit the incidence of high myopia. High myopia is associated with significant sight-threatening risks later in life such as cataract development, retinal detachment and macular degeneration.
There are various avenues for myopia control:
1.Orthokeratology: these contact lenses aim to control the progression of myopia by correcting for peripheral hyperopic defocus (which is thought to be a major contributing factor to the progression of myopia).
2.Atropine eye drops: Atropine is an anti-muscarinic drug that typically causes pupil dilation and cycloplegia (loss of accommodation). This can useful in diagnosing eye disease, improving amblyopia (lazy eye) and treating inflammatory diseases. However, when prescribed at these diagnostic and therapeutic concentrations, they can cause side effects such as blurred vision and glare. However, at low doses, it has been shown to be effective in controlling myopia with fewer associated side effects.
3.Multifocal soft contact lenses: this avenue seeks to control myopic progression by correcting for peripheral hyperopic defocus. They are the same lenses that are worn by people over 45 to help read clearly and are typically a monthly-disposable lens worn only during waking hours.
4.Time spent outdoors: Recent studies suggest that time spent outdoors is beneficial in reducing the progression of myopia. There is insufficient evidence at this time to know what factor is accountable for this protective effect. But more time spent outdoors (a minimum of 2 hours per day is recommended) with good UV protection doesn’t sound like too bad of an idea!
There are currently no published long-term studies that satisfactorily answer the question of how long myopia control treatment must be sustained. Clinical experience, however, suggests that children undertaking treatment must continue at least until the end of their teenage years. Alternatively, if the myopia has been shown to be stable for an extended period of time, then consideration can be given to discontinuing the treatment.