What is Myopia?
Myopia (short sightedness) is a result of an excessive elongation of the eye, where light focuses in front of, instead of on the retina. This causes distance objects to be blurry while close objects appear normal. Recent studies have shown that the prevalence of myopia is on the increase. (By over 70% in Asia & by up to 50% in the US & Europe). The earlier the onset of myopia in an individual generally leads to higher level of myopia in later life. Which increases risk factors for several ocular pathologies including glaucoma, cataract, retinal detachment, & myopic maculopathy. Brought about by the accompanying elongation of the eye in high myopia (>-6.00DS).
Risk factors for myopia & myopic progression
- One or both parents being myopic.
- Already being myopic (short-sighted).
- Being myopic at a young age.
What can we do to try and prevent myopia and its progression?
Strong evidence exists that spending time outdoors (more than 2 hours per day) can protect against the onset of myopia. Plus possibly reducing the final level of adult myopia. The total time spent outdoors appears to be the important factor, rather than the nature of the activity undertaken.
The association between near work and myopic progression has been evaluated in numerous studies and the outcomes were beyond doubt. Excessive accommodative demand caused by near work has been linked to myopic progression. Along with the resulting hyperopic blur. It is recommended to limit the time children are spent undertaking near visual tasks ie viewing mobile phones and tablets.
Spectacles and contact lenses
Recent theories & studies are now offering new suggestions and findings. One being that one of the reasons for myopic progression is that conventional spectacles and contact lenses are such that whilst the central image formed on the retina is in focus, the peripheral image formed by these lens designs is behind the peripheral retina. It is thought this may promote elongation of the eye as it attempts to form an image on the peripheral retina. By prescribing optical corrections such as multifocal spectacles and special contact lenses (orthokeratology and multifocal) we now have options to help slow myopic progression and improve outcomes for younger patients.
Studies have looked at pharmacological intervention (such as the Atropine for treatment of Myopia Study) to reduce myopic progression. But this option is not currently available in the UK. Single vision undercorrection was a popular option for myopia management. However randomised clinical trials unequivocally have shown not only does this strategy not work but actually can cause progression of myopia. Therefore is not recommended as a myopia control strategy.
Recommended available interventions
Multifocal or bifocal spectacle lenses
This is a lens correction with a reading zone in the lower part of the lens that reduces accommodative effort which helps reduce myopic progression. Various studies show this type of correction can reduce the final level of adult myopia by approximately 11-46%. Especially for individuals with additional near vision focussing issues (1).
Multifocal contact lenses
This works by allowing a clear central image to be formed on the retina whilst reducing the peripheral hyperopic defocus that is typically found in myopic eyes. It reduces the elongation of the eye. Various studies show this type of correction can reduce the final level of adult myopia by approximately 30-50% (2).
This works by flattening corneal curvature and reducing peripheral hyperopic defocus that is typically found in myopic eyes. Thereby slowing the elongation of the eye. Various studies have shown this type of correction can reduce the final level of adult myopia by approximately 32-63% (3).
- Brien Holden Vision institute – Myopia Management
- Optometry Today Volume 58:02 February 2018 – Myopia
- Review of Optometry July 2012 – Consider Ortho-K for myopia control
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