What is myopia?
Myopia,or short sightedness occurs when light coming into the eye is focused in front of the retina. This causes blurred distance vision. Most myopia is caused by the eye growing too long.
Myopia is increasing around the world with researchers now calling it an epidemic. It is thought that 30% of New Zealanders are myopic and at its current rate it is estimated that by 2050 five billion people will be short sighted. High myopia which is defined as -5.00 is an eye health concern. High myopia carries an increased risk of sight threatening conditions such as;
- myopic macula degeneration
- cataract
- glaucoma
- retinal holes and detachments
What are the risk factors for children becoming myopic?
- genetics-with both parents myopic carries a 6x risk factor
- prolonged periods of reading and close work including digital devices
- ethnicity-children with an east asian genetic background
- lack of time spent outdoors in the early rapid growth years
- eye muscle co-ordination and focusing problems
Mykidsvision.org (http://www.mykidsvision.org ) is a great resource and can be used by parents to assess the risk of myopia in their children.
Why do we want to slow myopia progression?
People who are myopic are more at risk of developing eye health conditions which can be sight threatening particularly later in life. The higher the degree of myopia, the higher the risk. So if we can slow down and prevent the progression of myopia to high levels then a significant amount of low vision or even blindness can be prevented.
What is myopia control?
Myopia control encompasses a number of techniques to slow down the progression in myopia over time. Myopia control fits well within the concept of preventative medicine. The key to myopia control is to stabilise the lengthening of the eye as this cannot be reversed so early control is important. However the progression of myopia is multi-factorial and is not fully understood. This means that the benefits of myopia control are measured over a population group and individual variability will occur. There are no treatments that stop progression of myopia completely.
What options are available?
- adaption of environmental factors-there is some evidence that spending at least 2 hours a day outside in natural lighting may decrease the onset of myopia but may little role once myopia is established.
- spectacle lenses-traditional spectacle lenses correct myopia by focusing light directly on the central retina to give a clear image-however the peripheral retina remains unfocused and it is thought that this is a driver for the eye to continue growing leading to increased myopia. Specially designed spectacle lenses -Myovision-have been developed to reduce this peripheral blur and the major lens companies are developing more options in this area. This is a good option for children who are not suitable for contact lens wear although not as effective as other forms of control. Also children who have problems with eye coordination with reading tasks may benefit from the prescribing of progressive addition spectacle lenses or specialised bifocal lenses.
- contact lenses- MiSight is a soft daily disposable lens designed at the University of Auckland. the most recent study with these lenses suggests a 59% reduction in myopia progression compared to a normal soft lens. Multifocal type contact lenses have also been found to have a positive effect on slowing the progression of myopia
- see http://coopervision.com.my/contact-lenses/misight
- atropine-low concentration atropine drops (0.01-0.02%) have a positive effect. The exact mechanism of effect is under going extensive research around the world but atropine probably affects a receptor in the retinal tissue signalling the eye to stop going excessively. Drops need to be instilled nightly and can be used in conjunction with other treatment modalities. Atropine drops at this concentration are not commercially available so will need to formulated by a specialised compounding pharmacy.
- orthokeratology lenses – these are custom design rigid contact lenses which are worn overnight while you sleep. They reshape the surface of the eye giving clear vision during the day without contact lens wear. By reshaping the cornea light is able to be focused centrally on the retina as well as peripheral light to focus in front of the retina removing the stimulus for the retina to further elongate. Tauranga Eyecare are currently researching this option in myopia management to select the best technology to offer to our patients.
Your optometrist will discuss the most appropriate and recommended form of myopia control for you.
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