What affects the focal point, leading to near- or far-sightedness?

Near sightedness is a condition whereby the eyeball is too long or cornea has excess curvature such that light entering the eye is focused in front of the retina rather on the retina itself.

The exact cause of nearsightedness is unknown but there are two factors that may be responsible  for its development.

1. Visual stress

2. Heredity

Individuals who spend considerable time reading or working at a computer or engage in other types of intense close visual work may develop nearsightedness.

There is credible evidence that many people inherit nearsightedness or are at least  predisposed to the condition, especially if both parents suffer from the condition.

Far sightedness (hyperopia) is a condition where the eye is shorter than normal, the cornea is not curved quite enough or the lens sits further back in the eye than is normal.

This condition can be inherited especially if both parents suffer from it.

The other cause is through diseases like diabetes or glaucoma.

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