As we have seen, the role of different transparent media of the eye is to make the image that we see is formed on the retina, the same way as in a camera, the mission's goal is to photograph the image is formed in the film. If so before or after the picture will be blurred.
A myopic eye is one which forms images from the infinity (from about 5 meters - as in the cameras -) before the retina. So the image that reaches the retina is blurred, thereby transmitted to the brain.
SYMPTOMS Thus, we can conclude that the first symptom of a myopic eye is poor distance vision.
But let's go deeper into some details: Light rays coming from infinity (again, from about 5 meters) enter the eye parallel and converge (form the image) before the retina. It seems logical that if entrasen rays diverge, converge closer to the retina, or even in the same retina. Or it would be less blurry, or even entirely clear. And when it does this? Quite simply when the rays (ie the image we want to see) is in a position close (within 5 meters).
So, we have another characteristic of myopic eye: A myopic looks bad from afar but looks good up close. However, it is clear that if a person is many diopters myopic to see well up close would have to get much anything you would like to see well, which is quite tired and uncomfortable.
CORRECTIONAnd how will correct a myopic eye? We have already given the answer: will that lead to retinal image that usually forms before it. And we have seen that if you go divergent rays, this fact occurs. So, will be placed before the eye a lens that produces this effect. And this makes a negative lens, whose main physical characteristic is that it is thicker at the edges than the center. And it is for this reason that the smaller the chosen frame and rounder (not peak), the crystals are thinner.
CAUSES And, why can image form before the retina, and not in place?
There are many causes. The most common include: An excess length of the eye, or an excess power of the transparent media of the same (due for example to a change in curvature of the cornea, or a change in the refractive index of any of they - because of a metabolic disorder, for example)
IS MYOPIA HEREDITARY? We can say that myopia has a hereditary component. Ie it is more probable that children go myopic parents myopic parents that no myopic. I would add that it is the "willingness" to what really inherited myopia. And linking to this:
THEORIES. There are many theories on the formation of myopia, but the most widespread is the MYOPIA SCHOOL. That is, if one eye has "willingness to be myopic" will shortsighted at the time be required visual effort near vision than usual. And this usually happens for the first time in my life at the time of enrollment. And hence I so often see myopia in these ages. And the explanation is quite logical: The eye is myopic effort just for the near vision is less (The human brain is a very wise). That is, distance vision is sacrificed for convenience in the nearby. But what if the child is correct myopia in full? Well, simply restoring the previous situation, and if the eye "gives of", will become even more myopic. And hence I so often something less than the total correct myopia, to give comfort for near vision. Even, in some cases usually corrected with bifocals, with a graduation for far and one for near, but this is the subject of another topic and other forums.
Así, se puede concluir que "la miopía es la adaptación típica del sistema visual a la visión de cerca" , pues como ya vimos, el ojo humano está preparado para una actividad esencialmente a distancia, con la posibilidad de adaptarse, por la acomodación, a la visión próxima.
If the eye does not "whether" (no predisposition myopic), there may be other problems, such as discomfort, fatigue, reading rejection, etc.., Which require other corrections.
COULD MYOPIA BE CURED? You can not "cure" myopia because it is not a disease. It can be corrected with glasses or contact lenses.
But always we have studied the method to eliminate nearsightedness and avoid the use of corrective lenses. We will mention some of those run:
Formerly there were many curious ways: The most traumatic was simply remove the lens in cases of high myopia, 10-15 diopters, which comes to the same dioptric power. Another curious way the cornea was removed, freeze it and mold it to vary its curvature and thus eliminate the problem. Hence the radial keratotomy was only one step. This method involves radial incisions in the cornea, thereby to vary its curvature and give less power, so that images are formed on the retina. And we come to the most commonly used today, which is broadly similar to the above but performed laser and appropriate calculations made with modern and complex computer systems.
But is surgery convenient? Well, well, this is tricky. The first thing to say that each case is different and it is essential to examine and advise the done by an ophthalmologist of confidence for oneself. My personal opinion is easy: DEPENDS. The truth is that the only disadvantages that arise are those of any surgery (which no longer an "aggression" to a healthy eye) You have to add another "risk": It remains to verify the behavior of a cornea operated after a long period of time (many years). Although in this regard the prospects look good. So you have to add everything in each case and assess whether it is worthwhile or not. I personally (I'm about 6 diopters myopic), I have no objection to wear glasses or contact lenses, and also my vision (yet) is excellent (with glasses or lenses, of course), but I understand why people do not support it as well, and this will involve a significant reduction in their quality of life. There would have to seriously consider this option. Also, consider that it is not always possible to reduce a hundred percent, leaving a remainder of myopia or astigmatism, although, of course not the same stay with a diopter for those who had five or six before.
And I would not end without reference to other less "violent" to eliminate myopia, such as VISUAL TRAINING and even ORTHOKERATOLOGY. Visual training involves a series of exercises, both visual and other kinds. Unfortunately it is a very common practice, since in some cases can provide excellent results.
Orthokeratology is to vary the curvature of the cornea contact rigid contact lenses adapted flatter than really necessary, to thereby "squish" the cornea and change its curvature. Its drawback is the "memory" of the cornea, which tends to restore the original curve, making it necessary to return periodically to treatment with the lenses.
WHEN DOES MYOPIA STOPS? In this, as in most related to the behavior of the human body, there is no exact rule and one hundred percent predictable. It seems logical that at the end of myopia development will not progress. And so in fact almost all of the cases. But it is not strange that they give significant increases of myopia when it has been left far behind the completion of the development. Every eye and every person is different, and influenced by many factors, from the purely physical to the environment themselves, or even the occupation itself. In any case, we return to something very repetitive, it is essential the Vision newspaper examination by an appropriate pofesional.
Of course, everything discussed above is applicable to the most common case of myopia, which is not disease and is a "refractive error" visual system. Unfortunately there is another kind of myopia, may be considered if disease is much less common though, which is not the proper place to discuss it.