There are different types of eye defect ranging from short sightedness, longsighted, astigmatism, presbyopia etc.
If someone is only able to see close ranged object clearly but not far distant object, then such person is suffering from short sightedness or myopia. This occurs when the light rays entering the eye does not converge on the retina. Instead of converging on the retina, the light ray is formed on a point in front of the retina. <em>This causes the distance from the eye's lens to the retina shorter compared to that of a normal eye. </em>This eye defect is usually corrected using concave lens in order to diverge the rays thereby allowing it to focus on the retina.
Hence, if the distance from your eye's lens to the retina is shorter than for a normal eye, you will struggle to see objects that are far away (at a far distant).
