Myopia Causes

There are many causes for Myopia. It can be hereditary. There was a greater risk for a child to get myopia, if both the parents have myopia. 

Myopia also depends on the structure of the eye. Myopics are known to have longer eyeballs. 

The amount of strain the eye goes through also plays an important part in people having Myopia. Children who play sports have lower chances of myopia. It can be because they use more distance viewing and low close up works.

There might be external, environmental reasons as well.

Axial myopia is attributed to an increase in the eye's axial length.Refractive myopia is attributed to the condition of the refractive elements of the eye. Curvature myopia is attributed to excessive, or increased, curvature of one or more of the refractive surfaces of the eye, especially the cornea. 

In those with Cohen syndrome, myopia appears to result from high corneal and lenticular power. Index myopia is attributed to variation in the index of refraction of one or more of the ocular media. (as per Wiki)

Elevation of blood-glucose levels can also cause edema (swelling) of the crystalline lens as a result of sorbitol (sugar alcohol) 

accumulating in the lens. This edema often causes temporary myopia.

Myopia is known to be present in greater percentage in urban areas than in rural areas. Studies do prove it.

Eating too much of refined white flour also is known to increase the chances of getting nearsightedness.

Symptoms of nearsightedness may also be a sign of variations in blood sugar levels in persons with diabetes or an early indication of a developing cataract.

An optometrist determines what the cause of myopia can be and treatments are done according to the medical condition of the patient and the cause for myopia in that particular person.