A better answer to you question would be to describe what we call refractory errors in the eye. Refraction is bending of light as it passes through one object to another. Vision occurs when light rays are bent (refracted) as they pass through the cornea and the lens. The light is then focused on the retina. The retina converts the light-rays into messages that are sent through the optic nerve to the brain. The brain interprets these messages into the images we see. Therefore any problems with the above system results in a refractory error.
In answer to your question, short sightedness also called near sightedness, is a refractory error where objects that are close appear clear, while objects far away appear blurry. It is because light comes to focus in front of the retina instead of on the retina. Another name for short sightedness is Myopia. So if someone is doing something that might have consequences in future but they don’t seem to realize that now you can warn them by saying don’t be myopic!