- Diet & lack of exercise contributing to myopia
- Myopic macular degeneration
- high myopia and glaucoma
- Some syndromes related to high myopia
- Myopic retinoschisis
Myopia occurs when light is focused in front of the retina. A minus lens will focus the light further back on the retina. enlarge
Another term for myopia is short sighted...that is everything close is clear, everything far away is out of focus and blurred.
Theoretically myopia can occur for 3 reasons...
Spectacles or contact lenses help most people see really well. But if you have significant myopia, and cannot wear contact lenses, laser refractive surgery may help. This another strongly recommends glasses and contact lenses. Children.
Axial length myopia...that is a large eye, may develop
'Ballistic' is the term used by Gregson to describe early onset rapid growth of the eyeball (it is not a generally used term). Rapid eye growth may occur in conditions such as the generic conditions below. In glaucoma, the eye reaches a high pressure, and the eye ball is 'stretched'. If the pressure is reduced to normal, then a normal growth pattern is restored. Staphyloma Eye 2013.
There are many known genetic causes of myopia.
Light hits the retina...amacrine cells in the retina release chemicals that slow down scleral growth. The growth factor acts on the chondrocytes in the sclera. enlarge
In healthy eye development, the retina can 'switch off' eye growth. In one experiment chicks are reared in the dark, and resulting in extra eye growth see. Effectively the light is controlling growth.
There is 2% reduction in myopia for every additional hour per week spent outdoors BJO 16. Also, ethnicity is important.
One current theory suggests that when stimualted by light the amacrine cells in the retina produce a chemical that influences the serotonin transmitter, and this produces a chemical that influences scleral chondrocyte growth. Amacrine cells somehow control eye growth by means of the ZENK transcription factor.
This 'visually guided' feedback pathway sees to be at fault in such conditions as
World wide the number of people with myopia is increasing, and dietary factors probably contribute, although school work and near work probably contribute more as above. Certainly, environmental factors are involved. Less exercise leads to less myopia and Rose 2008 and outdoor activity reduces it.
Environmental influences contribute to lower degrees of myopia affecting 5-45% of populations. Vvery high myopia (very high myopia is often associated with major ocular genetic problems as above. See increase in US myopia. Epidemiology Archives2011
One postulated dietary mechanism is that the
myopia increases in highly developed countries enlarge
Myopia is increasing. his seems to be due to a combination of