Nearsightedness and farsightedness are caused by what?

Answer 1

Nearsightedness and farsightedness are caused by light falling somewhere other than directly on the retina. Normally, light enters the eye through the lens and shines directly on the back of the eye called the retina. This is important because the retina is where all the receptors are, and they convert the light into nerve signals that are sent to the brain.

In nearsightedness, light comes through the eye and lands in front of the retina, causing images far away to appear blurred. This can be caused by a curvature in the cornea or lens that is misdirecting the light, or by the shape of the eye itself. If the eye is longer than normal, light may fall in front of the retina.

In farsightedness, light falls behind the retina, so that images close up appear blurred.This can also be caused either by the curvature of the lens or cornea, or by the shape of the eye. In the case of farsightedness, the eye may be shorter than normal.

Answer 2

Near-sight, also called short-sight or myopia, is caused by the main lens in the eye being too thick and powerful, and it is corrected by a negative (concave) lens. Far-sight or long-sight, hypermetropia, happens when the lens is too thin and not powerful enough, and is corrected by a positive convex lens.