Short-sightedness, also called Myopia, is a problem with the focusing ability of the eye. It is when the eye is not able to focus properly on objects in the distance. This condition is very common and it often occurs with many members of the same family. It happens when the cornea becomes a different shape (too curved) from usual or when the eye is longer than normal and so causes light entering the eye to focus on a point within the eye before the retina. This causes the eye and brain to see the image of the distant object as a blurred image. People with myopia often squint while watching television or trying to see distant objects. Myopia can often be the first symptom of Type II Diabetes.
Short-sightedness Facts for Kids. Kiddle Encyclopedia.