The vision problems can be varied, the most common are refractive, but other chronic or functional do not give a proper
To view it, you need the images reach the brain clear and correctly so that you can identify and prosecute, when this happens, we say that the eyes are normal or emmetropic.
But when the images do not reach a clearly defined because the light rays coming to a focus or inappropriate location of the eye, there is distortion-dependent eye problem and this is called abnormal or ametropic eye.
The main problems of visual refraction are:
– Myopia. It occurs when light rays focus in front of the retina instead of directly on it, causing nearby objects easily visible, but far are difficult to distinguish. This problem is due to deformation of the eyeball, which appears stretched or because the lens has a focal length less than normal and corrected with concave lenses which extend the focal length or refractive surgery.
– Hyperopia, when light rays projected image at a point behind the retina, making nearby objects appear blurry. This problem is caused by a cornea or lens curvature with little or because the anteroposterior axis of the eye is shorter. It consists convex lenses are thicker in the center than at the edges and shorten the focal length or refractive surgery.
Astigmatism occurs when there is deformation in parts of the cornea, the transparent membrane covering the eye, causing it not to form a focus on the retina, but a mixed picture often incomplete or distorted. Lenses that correct this problem is cylindrical, which direct light rays to a single focal point. Also corrected with refractive surgery. This problem causes pain in the eyes and head and a lot of eyestrain.
Other problems that affect vision are:
Farsightedness or presbyopia. Also known as “sight” and develops with age. It is caused by hardening of the lens, you lose some elasticity. Usually starts to appear after age 40 and have the person who has to ward off small to see objects clearly. Is corrected with glasses for near and / or with different strength in each eye, which should be changed regularly until about 65 years of age, when the problem is usually no longer increases.
Color blindness or color blindness is a condition that prevents the cones of the retina to distinguish all colors or certain color tones. Most do not distinguish between red and green and others can not do it between blue and yellow tones. There is no cure for this deficiency, if the problem worsens, stained glasses can be suggested to distinguish between colors that are confused.
Amblyopia, also known as “lazy eye syndrome or lazy eye” is the partial loss of vision in one eye. In rare cases this problem can occur in both eyes, with clear signs of tremor or involuntary eye movements.
It is caused mainly by the presence of strabismus and eye fixation “normal”. Another cause may be anisometropia or difference of graduation from one eye to another, causing a delay of the visual capacity of the defective eye. It is also caused by congenital cataracts.
Strabismus: Better known as “crossed eyes”. This condition is characterized by loss of parallelism of the eyes, meaning that while one eye looks at an object, the other is deflected in another direction resulting in many cases a striking aesthetic defect. This is mainly due to the alteration of the eye muscles attached to poor vision, ie, one eye turns it looks bad and looks bad because it is twisted. The problem is corrected by using lenses with special glasses, occlusion of the deviated eye patches, muscle exercises and in some ways by surgery.
But there are also functional as the chronic or glaucoma, keratoconus, diabetic retinopathy, the cataracts among others, to be detected in time to serve them properly.