ASTIGMATISM 
Astigmatism is a common visual distortion caused by an irregularly shaped cornea. The light rays pass through an irregularly shaped cornea and produce two different focal points, with the result of blurred vision at different distances.
May contribute to astigmatism factors such as the low level of light or fatigue, although it is usually a hereditary disease. The symptoms of a person with astigmatism are strabismus, occasional episodes of headache and eye strain
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HYPERMETROPIA
When an eyeball is too short for the power of focus of the lens and cornea occurs hyperopia, and then the light is focused behind the retina. Close objects appear blurry while distant ones you see more clearly, thus creating a situation of reduced visual acuity when the subject looks up close. The correction of hyperopia is important at a young age through a lens "positive" that allows a clear view of nearby objects.


MYOPIA 
Those who suffer from myopia sees objects clearly within a certain distance while the distance vision is still blurry. In most cases, this condition occurs when the eyeball is too long for the power of focus of the lens and cornea, and makes the eye too powerful focusing the images in front of the retina. The problem is solved with the use of a lens "negative" to "weaken" the eye so as to allow the most correct myopic vision. Important to prevent this disease is proper nutrition, improve posture and proper use of assets to be nearby such as reading and computer use.

PRESBYOPIA 
Presbyopia is caused by the natural aging and hardening of the crystalline lens of the eye that after 40 years it thickens and begins to lose elasticity by decreasing the eye muscle control. The so-sighted meets increasing difficulties having a blurred vision of near objects. Among the symptoms of this disease are having eye strain and tend to keep away from eyes from the object.