Elliott+Eyesight+Correction

The human eye can be either to short or too elongated, resulting in vision of farsighted (can't see close to you) and nearsightedness (can't see far away). Depending on this, will determine the shape of corrective lens one will recieve, either convex or concave. A person with farsightedness has a shorter eye which causes the retina to be closer than wanted. This uses a convex lense to correct because the focus is behind the eye, where the retina should be.