There isn't any predetermined schedule for changing glasses or contacts. It is important to vary your prescription only when it no longer provide enough correction. However, it's still a good idea to haveregular eye examinations.

The light is concentrated by the cornea and the lens onto a thin layer of tissue known as the retina, which covers the back inside wall of the attention. When the targeted gentle hits the retina, a picture is taken. Messages about this image are despatched to…