The average person blinks 10,080 times every 14 hours. An eagle can see a rabbit about 1760 yards away but the average human can only see the same rabbit from 550 yards away. The most complex organ in the human body, aside from the brain, is the eye. The eye has over 2 million working parts and processes 36,000 bits of info every hour. The human eye can see a candle 14 miles away, conditions allowing. Eighty five percent of the total knowledge we receive comes from the eyes in a sighted person. The eyeball in a human adult measures 1 inch in diameter but only 1/6 of it is exposed.The external eye muscles are 100 times stronger than necessary. Your eyes use 65 percent of the total pathways to your brain.

Picture Source:NASA

Nocturnal animals such as the owl have more rods in their retina, because of this they see better in the dark, and their eyes are tubular which increase the light to the lens which goes to the retina.

Dogs only see in shades of gray.

Fish require no lubricant in their eyes like tears since they are always in water. Fish have no eyelids.

Insects have compound eyes. They have many lenses that can not focus. Their brain takes all these images and makes one image from it. They have a much greater field of view than we do.

When an embryo developes, the Pituitary gland developes near the eyes and later in development moves up to the brain. Is this the mythical third eye ? Some animals (reptiles such as some lizzards and snakes) have a third eye in the middle of their forehead that detects light, but can not see. It is used to control body temperature.

Picture Source: US Bureau of Land Management

The sharpest vision belong to the hawk since it has two foveae and the maximum amount of cones. Every year about 40,000 people get a corneal transplant. The oldest person to get one so far was 103 years old.

Picture Source: US Bureau of Land Management, Photo by Larry Ridenhour

A Raccoon's eyes glow at night because light bounces off a reflector at the back of the raccoon's eye. The reflector doubles the amount of light the eye can use, and helps the raccoon see more at night. Horses and some breeds of dogs can not see directly in front of them. This is why it is so important to give a horse a loose reins after it takes off for a jump so it can move its head to determine its landing. The mole has the smallest eyes of any animal, they only measure 1 mm in diameter. Jellyfish have a primitive eye, but it doesn't seem their brain can process the sight information. Bulls are color blind so if you wave a cape in front of one it could really be any color.

Picture Source: National Park Service

The eye of a dolphin has 7000 times as many rod cells as a human eye, enabling it to see in deep water. Some animals such as the Flounder have markings on their body that look like eyes as do some moths.

Picture Source: National Marine Mammal Laboratory, Scott Hill, NOAA Corps

The vulture as a milky membrane over its eyes that serves to keep out bright light and dust. Flies have lots of little holes, where there eyes would be, which are actually hundreds of separate little eyes. Scallops and clams are seen to have 1-2 rows of eyes around their shells that enable them to look in every direction and allows them to sense movement but the shells must be open for them to see. The starfish, conch and snail have eyes at the end of their tentacles, this provides them with the ability to poke out a tentacle from behind a shell or other type of protective shelter, without putting its whole self in danger.

Picture Source: EPA

Nocturnal animals tend to have big eyes, in proportion to the size of their body and pupils that open far wider in low light conditions than those of diurnal daytime animals. Nocturnal eyes gather more light than other eye types do. While we may think some appears completely dark, the nocturnal animal may see it as dimly lit.

Picture: Nutria

Picture Source: US Fish & Wildlife Service

The flatworm has 2 crude eyes with very limited vision. The octopus has a fairly advanced camera type eye, with an active rectangular iris which contracts to a narrow slit. It can focus its eye lens for near and far vision, but does not have well-defined vision, like humans. Scorpion eye design is really different in that they may have zero to twelve eyes. The average is about eight for most of the common types.

Picture Source: USGS