Myopia and hyperopia

Myopia and hyperopia are the leading causes of bad eyesight. Both have to do with the shape of the eye. In myopia, the eye is deeper than normal. In hyperopia, it is narrower.

Look at the pencil on your desk. The light reflected off that pencil enters your eye and hits the retina, like a movie being projected on a screen. The retina is like the movie screen. When the eye is the perfect shape and the retina is the perfect distance from the lens, the image is in focus. When it’s blurry, you might be able to make out colors and the general shape, but you can’t see details, like whether the pencil is sharpened or the eraser has been used.

Imagine the screen at the movie theater being moved away from the projector by a few feet. If those beams of light come into focus before hitting the retina, like they do with myopia, the light will only scatter again before finally hitting the retina. The image will be blurry.

Now imagine that movie screen moving closer by a few feet. If the beams of light don’t meet up until a point past the retina, or screen, the image will also be blurry.