Tuesday, 22 January 2013

Literature Review on Myopia by Lim Ing

                          Literature Review on Myopia - Reducing Myopia Progression

                                                         Lim Ing       (03)      S203 21/2/13

For many decades, efforts have been made to reduce the progression of myopia. Up to now, there has not been very convincing evidence that anything works because myopia progression studies are very difficult to carry out and they take a long time to complete. Because a genetic factor is involved, the answer may lie in genetic therapy. So far, the following methods have been tried. Some of them have been proven to work in one or two clinical trials, but more trials are needed to verify these results.
Eye-Drops, such as atropine, pirenzipine and cyclogyl. They relax the focussing muscle of the eye. It is also said that some of these eye-drops prevent the eye from growing longer. A few studies have shown that such eye-drops do work, but then they have side-effects such as blurred vision, glare, allergy, and the risk of developing glaucoma. Myopia returns rapidly once the drops have stopped.
Contact Lenses
Ordinary hard (Rigid Gas-Permeable) contact lenses have been used, and there is anecdotal evidence that they work. However, clinical trials have been unable to corroborate this finding. The lenses tend to cause eye irritation, especially in dusty environments.
Orthokeratology lenses 
(A special type of contact lenses) alter the shape of the cornea (corneal flattening, as in Lasik). These lenses are worn by the child when they sleep, and are removed the next day. The child will be able to see without glasses or lenses but the cornea very quickly regains its shape. There have been several cases of corneal ulcers because of these lenses. Whether these lenses can reduce the rate of progression of myopia has not been proven.
Optical Undercorrection
Some practitioners believe that wearing glasses that are undercorrected for the myopia will slow down the progress of the myopia. Again no convincing evidence is available to support this but a recent study of children wearing monovision glasses (i.e. with one lens undercorrected) showed that the eye wearing the undercorrected lens did not progess as rapidly as the eye wearing full correction.
This method is training the brain to see better even though the degree of myopia has not been reduced. One study showed that neurovision reduced the progression of myopia as well. However, more studies are needed, to verify this. 
Outdoor Activity:
A couple of recent studies have shown that children who participate in more outdoor activity have less myopia.
Nutritional support in the form of Vitamin A, C , E, Omega-3 and Lutein should be good for the eyes.
Lowering Intraocular Pressure:
There are some who think that the increase in axial length of the myopic eye is due to increased intraocular pressure. The raised pressure is said to be due to pressure from the eye muscles to converge the eyes and the stooping posture of the head when reading. It is also said that lying down to read increases the eye pressure. There is no convincing evidence to prove all these. Studies done to reduce the IOP in myopic children have not shown any effect on myopia progression.
Many of the myopic progression reduction methods are not clinically proven or tested yet. Some of them can even harm and make the situation of the eye worse. This shows that the technology now can help reduce myopic progression but still need further testing and improvement. 
Data Collection: 
According to the website, they had clinical tests done on each myopic progression reduction method to see if they were or were not reliable. 

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