The Eye

The eye works like a camera, taking pictures that the brain processes. For vision to be clearly processed by the brain, an accurate and clear picture must be focused on the retina, the inner lining at the back of the eye. It is important that the image is formed on the retina. If the image is formed in front of the retina, then only close images are clear (short sighted or myopia) and if the image is formed behind the retina then only images at a distance will be clear (long-sighted or hyperopia).

Anything degrading the image reaching the retina will reduce vision, such as a cataract or corneal opacity. Further, even if a well focused image is formed on the retina, anything distorting the retina will degrade vision such as swelling or bleeding. The latter is seen in diabetes and macular degeneration.

The image is converted from the retina to electricity and sent via the optic nerve to the brain. The optic nerve can be affected by various conditions such as glaucoma.

Finally the brain has various areas devoted to the processing of vision. Conditions affecting the brain's visual centers will affect an individual's visual perception.