human vision vs. animal vision

How is the human eye different to the animal eye?

the human eye

The human eye has three types of cone receptor cells present in the retina which is known as tri-chromatic vision. These cone receptor cells are situated in a small area of the retina known as the fovea and allow us to have highly focussed and exquisite colour vision. Cone receptors function primarily during daylight conditions and therefore we are able to receive and interpret millions of colour signals during the day.

A second type of photoreceptor is present in the human eye which is known as rods. Rods are responsible for detecting the luminosity (brightness) of light and are used primarily during low light conditions. Due to the absence of rods in the fovea, humans generally have no colour vision during night time.

the animal eye

In contrast, the animal eye has only two sets of cone receptor cells which are also referred to as dichromatic vision. Due to vast differences in the animal eye structure when compared to the human eye, these cone receptor cells are scattered across the entire retina which spread their daylight vision in all directions with no focus on any particular zone. Also present in the animal eye are rod receptors. These receptors function mainly during low light or night time conditions while the cone receptors function during daylight hours.

The animal eye also has a light reflecting layer situated at the back of the eye which allows its receptors a second chance to absorb light. However, this reflecting layer also causes blurred vision during daytime conditions. The bigger eye with a rectangular aperture forfeits sharpness while trying to compensate for the large amount of incident light.

The cones and rods are connected to neurons which feed visual images to the brain. In the case of animals, large quantities of receptors are connected to the same neurons which increase sensitivity with a loss in high definition colour vision.

Due to these differences in eye structure as well as the different distribution ratios between cones and rods in the human and animal eyes, deer, antelope and buck do not have the same colour acuity as humans do and therefore have very limited colour vision.