MYOPIA CONTROL
What is myopia?
Myopia is a condition where a distant object is focused in front of the retina resulting in blurred distance vision. Myopic eyes tend to see better up close than in the distance – hence the term short sightedness.
Why do people become short sighted?
We do not exactly know why, but we do know that the following have a role:
- Family History – children are more likely to be myopic if one or both of their parents are myopic, particularly if the degree of myopia is high. Our genetic background also greatly influences the prevalence and degree of myopia, in Singapore 70 per cent of children are myopic.
- Environment – People in urban environments have more myopia than people in rural areas.
- How we live – Children develop high rates of myopia when sent to school but it is not clear if it is the amount of close work we do or the amount of inside time which causes this. People who spend more time outdoors are less likely to become myopic even if their parents are myopic and even if they read a lot.
- Peripheral Vision – in a myopic person using conventional contact or spectacle lenses, light from peripheral objects tends to focus behind the retina. This can act as a stimulus for the eye to continue growing longer and thus increasing the degree of myopia.
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Why does Myopia progress and can we stop it?
We do not exactly know why, but we do know that the following have a role:
There is an enormous amount of research being conducted worldwide around the topic of myopia and myopic progression. We cannot stop myopic progression, but we now have a number of options to slow it down. These include myopia control spectacles, Mi Sight contact lenses, and orthokeratology.
It has been known for a long time that when an eye starts to become short sighted the eyeball grows in length. When an eyeball grows then the image of the objects that you are looking at is focused in front of the retina, instead of being focused clearly on the retina itself – we call this myopic defocus. At this point traditionally we would recommend glasses and/or contact lenses to restore clear distance vision.
When a myopic person wears traditional glasses or contact lenses, light from central objects are focused clearly on the retina. However, light from peripheral objects is focused behind the retina and is termed hyperopic defocus. This hyperopic defocus has been found to act as a stimulus for the eye to continue growing longer and thus more myopic. See Figure 1.
When peripheral objects are focused in front of the retina (i.e myopic defocus) researchers have found that this sends a signal to stop or slow eyeball elongation and thus reducing the rate of myopic progression. See Figure 2.
There are a number of treatment options available that have been found to have an impact on the growth of the eye, and thus the progression of myopia.
Zeiss Myovision myopia control spectacles – To be worn full time or interchangeably with the Mi Sight daily soft contact lenses. The Zeiss Myovision spectacle lens corrects central vision so that the distance vision is clear, but alters the peripheral image so that this is placed in front of the retina (myopic defocus). This sends a stop signal to the eye to manage eyeball elongation and thus slowing the rate of myopic progression. Research on children up to 12 years of age has shown that myopic progression can be slowed by up to 30 per cent.
Orthokeratology – Orthokeratology is the fitting of rigid gas permeable contact lenses that are worn whilst sleeping every night. The lenses gently reshape the cornea so that when you wake and remove the contacts your vision is corrected, allowing you to see clearly at all distances without spectacles or contact lenses. The effect can be easily reversed by simply stopping the contact lens wear. Myopic progression can be slowed by up to 50 per cent using orthokeratology, and is achieved by peripheral myopic defocus. At present Matamata Visioncare is unable to provide Ortho-K but we are happy to refer you to Hamilton for this.