Biology of the eye

This page covers all the content about the biology of the eye.

You need to know:
 * How eyesight works
 * Structure of the eye

How do we see?
Vision - the biological process of seeing

Perception - the psychological process of making sense of the visual image

The structure of the eye
Retina: The light-sensitive cells in the eye are in the retina, a layer at the back of the eye.

Rods and Cones: They are two types of retina cells. Rods are able to work in dim light, and only detects black and white. Cones are able to work in bright light, and can detect different colours

Optic Nerve To help us see, nerve impulses are sent from the retina to the brain. They travel down the optic nerve and to our brain. 

 Blind spot: At the point on the retina where the optic nerve leaves the eye, there is no space for any rods or cones. This little area is therefore ‘blind’. The blind spots don’t overlap, if one eye can’t see something, the other one can.

The optic chiasma: Information from the left and right eye crosses over at a point called the optic chiasma. This is the shape of the nerves as they cross over on the way to the opposite side of the brain. Information in the right eye goes to the left side of the brain, information in the left eye goes to the right side of the brain.  Visual cortex: From the optic chiasma, visual information is carried to the back of the brain. Many perceptual processes happen in an area of the brain called the visual cortex. The job of the visual cortex is to interpret the information from the rods and cones.The visual cortex uses this information in perception to understand shapes and distances, and filling in the gap left by the blind spot in each eye. This is why a pattern looks complete even though part of it may fall on the blind spot.