Differences in Human & Animal Eyes

Though humans are a part of the animal kingdom, there are many developmental differences between the human body and the animal body. The eye is one of those differences. The eye, or the body's camera, is similar in both animal and humans in that it uses a pupil, retina and focusing lens. Through adaptation, and because of different needs and requirements, the eyes of humans and animals have many differences.

Tapetum

• A tapetum is a structure beneath the retina that reflects light back through the retina. Horses, cows, dogs and cats have a tapetum. This allows the animal eye to capture more light, which gives nocturnal and night-active animals more opportunity to see at night. The tapetum is also the reason that some animals' eyes glow green or yellow at night when light shines on them. Human eyes do not have a tapetum.

Fovea

• The fovea is a part of the human eye in the retina that is high in cones. The retina contains two different types of cells: rods and cones. Rods sense motion and work in low-light conditions; cones are best used for bright light and detecting differences in colors. All mammals have more rods than cones, but human eyes have a fovea, which allows for more distinction in color and bright lights.

Nictitating Membrane

• A nictitating membrane is a piece of tissue that moves across the eyeball and acts as a third eyelid. Present in most animals, this third eyelid is rarely visible and can indicate poor eye health if it is visible. Human eyes do not have a nictitating membrane, just the upper and lower eyelids.

Cornea

• The cornea is a group of clear cells and proteins that constitute the outer layer of the eye. Its purpose is to act as a guard for the front of the eye and acts as a refracting lens. The cornea helps to shield the eye from harmful debris and functions as a window that controls the entry of light. The corneas in dogs and cats are distinctively larger in diameter than human corneas.