Vision Problems

Near Sightedness or Myopia

Commonly known as near-sightedness, myopia is a condition where the eye cannot focus on images at far distances. Most often, this problem is caused by the back of eye being too long, and hence the images that people see are out of focus. As mentioned previously, the eye see objects from infinity at "rest", and sees objects closer by adjusting the lens so that image focuses at the back of eye. For near-sighted people, the elongation of their eye results in light coming in from infinity (or far distances) to become out of focus, no matter how the lens adjusts. This results in distance objects looking blurry.

Despite the extension of the eye, the lens is still able to focus so that objects closer can be seen. The lens stretches out, and reduces the focal length of light, which allows it to hit the back of the eye.

Far-Sightedness or Hyperopia

Hyperopia occurs when the back of the eye is closer than is should be. In this case, the individual can see objects from far distances, but cannot see objects from short distances. When light from infinity hits the far-sighted eye, is doesn't focus. However, the eye can compensate by adjusting its lens and shortening the focal length. This allows a focused image to be cast on the back of the eye.

However, because the lens only has limited strength, it can only adjust the lens so far, and cannot focus on objects that are up close. This causes images that are closer to remain out of focus, and the diagram shows.

Spherical lens can be used to correct our vision by "enhancing" our own natural vision. You can read more about that in the next section.

Colour Vision
Colour Math
Focal Lengths and Distances
GRIN Systems
Human Vision
Vision Problems