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Myopia

Generality/Definition
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    Myopia, or nearsightedness, is a very common condition affecting one's distance vision. The light that enters the eye through the cornea and the crystalline lens is bent in such a way that the resulting image focuses not on the retina (the light sensitive inner wall located at the back of the eye), but in front of it. A concave lens can be used to correct the image.
    Source: Provisu look Myopia (uniteforsight.org)
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Symptoms

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Treatment

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    The excimer laser ( excited and dimer ) is using a fluorine and rare gas ( argon ) mixing. Its use allows not to have contacts between the instrument and the cornea ( avoids an infection ). Sending a ray in the UV spectrum has the consequence to pulling off the molecules. It sprays a cornea film at each impact ( around 0.25 m ). The fineness of the cornea films vaporized is the reason of the correction's accuracy of the excimer laser. The operation The intervention takes place on local anaesthesia, with using just a collyrium a few minutes before the operation. It will allow to anaesthetize the cornea. The patient is installed on a surgical armchair to ensure a perfect position under the laser. Using a retractor allows to maintain the eye in the opened position without pain or any risk. The surgeon must take off the epithelium to do this intervention. It's possible then to ablate directly in the corneal stroma. There are many existing techniques: the first one consists in using a surgical spatule and to scratch the eye's surface. Anyway, the most used technique is the use of a brush, which takes off a cylindrical surface of epithelium, superior than the zone to treat. The practicians prefer yet to use again a surgical spatule on the surface. To obtain correct results, it is necessary to remove epithelium of the zone to treat. There is an other technique mainly used, which consists to expose the epithelium with an alcoholized solution, in order to peel it and to remove it with a surgical spatule. The practician draws now the central aim with a corneal marker and he asks the patient to watch a light situated in the center of the ray. It's possible to begin the treatment. The operation is very short and allows then to avoid a decentralized treatment. When the eye is moving a lot, the treatment must be immediately stopped. When the eye becomes stable again, you can continue to operate. At the end of the intervention, some healing drops can be added on the eye and some analgesics are also prescribed.
    Source: Provisu look SHORTSIGHTED/NEARSIGHTED EYE (myopes.com)

Illustrations

Source: Provisu look SHORTSIGHTED/NEARSIGHTED EYE (myopes.com)


A normal eye and a shortsighted/nearsighted uncorrected eye

Source: Provisu look SHORTSIGHTED/NEARSIGHTED EYE (myopes.com)


A correct shortsighted/nearsighted eye

Source: Provisu look SHORTSIGHTED/NEARSIGHTED EYE (myopes.com)


The laser has ablated one part of the cornea ( orange part ), which offers a flatter refraction surface.

Source: Provisu look Myopia (uniteforsight.org)


The light that enters the eye through the cornea and the crystalline lens is bent in such a way that the resulting image focuses not on the retina (the light sensitive inner wall located at the back of the eye), but in front of it. A concave lens can be used to correct the image.

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Last modified: Jan 2014
Creation: Feb 2006