Microlight » Human Factors » Vision

The Eye

Our eyes allow us see the visual image of the environment. 

They act like a digital camera. 

They collect light rays reflected from an object.

The lens then focuses these rays into an image on a screen (the retina).

This image is converted into electrical signals that are then sent via the optic nerve to the brain. 

There are two kinds of light-sensitive nerve endings at the back of the eye.

The Cones - which see in colour and require considerable light to work, and

The Rods - which can see objects only in shades of grey but can operate in very dim light.

Cones 

Our vision in bright or moderate light is completely mediated by cones, which provide colour vision, black and white vision, and high acuity, the ability to discern fine detail.

Cones are spread throughout the retina but are especially concentrated in a central area called the fovea. 

When we want to read or inspect fine detail, we move our heads and eyes until the image of interest falls onto the fovea. 

Because the fovea lacks rods, it is easier to see in dim light by looking to the side of an object instead of directly at it. You can test this by looking to the side of a faint star so that its image falls on rods, rather than on the fovea where it probably will not register. When you look directly at the faint star, it disappears.