What is myopia?
Myopia, nearsightedness or short-sightedness is an eye deviation which makes distant objects look blurred, while objects up close can be seen clearly.
Myopia is not a disease, but a refraction abnormality (refractive error) in the optical system. To see clearly, both the cornea and the lens must break up light rays and project them onto the retina; a layer of light-sensitive cells that line the interior surface at the back of the eye (fundus). Here, light is converted into electrical impulses that are then transmitted to the brain via the optic nerve.
A myopic eye is longer than the ‘normal’ eye. If the eye is too long or if the lens is overly curved (bulbous), the focal length of the lens will be too short and the image is then projected too far in front of the retina, creating an out of focus image.
About 30% of the western population is nearsighted. Myopia usually starts to develop from 8 to 12 years of age and can continue to evolve throughout adolescence. This refractive error usually stabilises in adulthood.
People who are nearsighted can see close up objects more clearly than those far away. Those in the early stages of myopia like to sit closer to the television or the blackboard because they have trouble reading. An untreated ‘myopic’ is often recognised by their tendency to squint. Adults might have difficulty driving in the dark.
It is not yet entirely clear why short-sightedness develops. Myopia is partly hereditary, but because it has increased considerably in recent decades, environmental factors may also play a role. Possible causes are:
- Work which involves a lot of close-up activity (e.g. reading, studying, computer use). Children today are often busy doing ‘close-up activities’. Eyeball development can be affected when these activities take place for hours at a time. Myopia is also more common among highly educated populations
- Children who don’t engage in many outdoor activities (sports, playing outside) seem to have more chance of developing myopia. Natural light exposure levels have a great influence on whether someone is/is not myopic
- The parent’s refractive error. If both parents are myopic, there is a greater chance that their children will go on to develop a refractive error, too
- Other pathologies such as cataract and hyperglycaemia, for example
Myopia can easily be corrected by wearing glasses or contact lenses which place a negative or concave lens in front of the eye so that the focal point is moved back to the retina.
Another option is to undergo a laser procedure in which the cornea is made less bulbous. This is suitable for moderate myopia.
If the refractive error is excessive (high degree myopia), glasses lenses become very thick at the outer edge and contact lenses can not be tolerated. Laser treatment is no longer possible because too much corneal tissue will need to be removed. In this case, lens implants (refractive surgery) can offer a solution. An extra artificial lens is surgically placed within the eye, or the natural lens can be replaced by an artificial one.
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