It is a defect of vision which is manifested by the inability to distinguish objects clearly at a greater distance.
In myopia, focusing is performed in front of the retina. Myopia is measured in diopters, which are negative.
This is because the image objects / shapes are focused before the retina and because the myopic persons eyeball is elongated before or after.
In the figure below you can see how the image is focused before the retina, where myopic person. When you go to your ophthalmologist and dissenting recommended glasses that will correct the defect of refraction.
Causes of Myopia
As you already know, myopia occurs when the eyeball loses its shape perfectly spherical and lengthens front or rear.
A cause of the occurrence of myopia, is the fact that the eyes are not resting when tired. No offers eye rest they need after long hours of continuous use.
Another thing that leads to myopia, the eye using only short distances - working at the computer or reading - so your eyes adjust to see well only in the environment they are used the most.
Although myopia can not be cured, treatment can restore to normal or near normal. Treatment options include corrective lenses (glasses or contact lenses) and surgery. Using glasses is the most common method of treatment.
The lenses are light entering the eyeball to be focused on the retina.
Glasses and contact lenses are the preferred treatment for most patients with myopia.
It is a condition that is manifested by blurred vision. People who suffer from hyperopia see well at distance and see distant objects closer than they are normally, although the disorders are also close vision and distance vision. These people often have trouble focusing close ups and can not perform activities such as reading or sewing.
Farsightedness occurs when the anterior-posterior diameter of the eyeball is smaller than normal. This causes light rays entering the eye is not focused on the retina, but behind it. Hyperopic patient sees objects both nearby and far vision, blurred. As with myopia, hyperopia can be corrected by wearing glasses or contact lenses, or surgery (to no longer need glasses or contact lenses).
Symptoms occurring in Hyperopia
Do you have times when your eyes are tired and it is difficult to keep your place when reading? Did you tend to read the same row multiple times, strong headaches and dizzy? These are some symptoms of hyperopia as follows:
- Redness of the eye
- Tendency to remove what you read
- Frequent watery
- Nervousness arises due weight focus
It is a quite eye diseases are common, especially among children. Can be corrected easily by contact lenses, glasses or even surgical interventions Astigmatism occurs when the cornea is abnormal and shows curubri rather oval shape than round. Astigmatism is relatively common in the population: experts ophthalmologists believe that 3 out of 10 children aged between 5 and 17 years have astigmatism.
Causes of astigmatism
Frequently abnormal bulging of the cornea is shaped ellipsoid, this deformation can cause myopia (short sight) or keratoconus or keratoglobus has commonly occurs in both eyes manifested less frequently as presbyopia myopia (female / male ratio is 1:2).
Virtually all people have astigmatism. It is physiological astigmatism (0.50 to 0.75 dpt) for not requiring optical correction, accompanied by normal eyesight. Existing from birth, it may be accompanied by a slight evolution and is called congenital. Astigmatism can also be acquired, one of the determinants surgery, and various eye diseases such as keratoconus and pterygium.
Somewhere after the age of 40 years, everyone finds an unpleasant visual phenomenon, blurred vision almost exactly to read, to work on your computer, sewing, etc.. This is normal, no exception, sooner or later, even those who have never had eye problems that have not worn glasses will find this is called presbyopia. Problems and writing, may be present headaches or tiredness without apparent cause. At the moment there are no known ways to prevent this fenomen. As a treatment of this "inconvenience" we have glasses, contact lenses.