What causes myopia?

All types of myopia, regardless of the age it starts, cause blurry vision for things far away. The size and shape of your eye changes how light is refracted or reflected on the back of your eye. In myopia, your eyeball may be too big, or your cornea (the transparent surface of the eye) may be too curved for the light to reflect correctly. Changes in the size or shape of your eye generally occur during development prior to birth or in growth periods. Myopia tends to run in families.