Many Kind of Animals Eyes

Animals eyes are classified vary on this world. Eyes are an organ that base on the light come different each others, there are about 32 kind on animals world, that principally different work. The most complete of eyes like a camera that can absorb of wide spectrum like on primate such as monkey and human.

Eyes model of many animals is vary, and for human all eyes is located in the fronts that sometime have a blind spot area that cannot be seen. If we lay 2 same drawing of cat or other drawing with a distance of about 15 cm, then locate in front about one arm, close one of your eyes then move that drawing close to eyes slowly, on certain distance then one of the drawing will lost.

Octopus eye is an example of better eyes structure than primate in, the blood vessel located before the light recipient. So the octopus eye design is better than the human eye!

Our eyes are an advance design because can use as camera SLR and autofocus, auto exposure (fast adapt from dark to light by opening the diaphragm). If on the insect eyes they cannot adapt vastly and fish eyes just fixed focus like plastic camera and dog eyes are color blind.

Human eyes are stereoscopic (can suspect the distance from sight), using comparison software can compare the parallax distance and this technology still don’t imitate by human equipment.

Eye in Invertebrates

The light receptors of many invertebrates do not form definite images; the simply register light or dark or the direction of a source of light. The simplest such animal eyes are the light sensitive patches found on the flagella, or limblike projections, of the protozoan Euglena and the eyes pots of certain flatworms called planaria. Some organisms that have evolved true eyes have also retained simple photoreceptors of this type. Examples are the so called ocelli found in the lobsters and in the brain area under the skull; these organism can perceive light even when their true eyes have been removed.

Detection of Light
Despite the variety of types of eyes, the chemical process that transforms light into nerve impulses in the eyes is basically similar in all land vertebrates and marine fish, and in some insects. In 1967 George Wald of Harvard shared a Nobel Prize for physiology or medicine for discovering the details of the first step, which occurs in the retina or ommatidium.

The substances in the retina that detect light are called photosensitive, or visual, pigments. The major pigment in the eye is rhodopsin, or visual purple, which is composed of two distinct parts; a protein molecule called opsin, and a molecule made from vitamin A called retinene. When light strikes rhodopsin, the opsin portion, this leads, through a cascade of chemical reactions, to nerve impulse that relay visual information to the animal’s brain.

In the dark, and with the aid of chemical energy obtained from metabolism, retinene and opsin are recombined and rhodopsin is reconstituted. In very intense light, visual purple may be split faster than it can be reconstituted. Vision may then become impaired, for example, as in so called snow blindness. Vision many be similarly impaired if vitamin A is deficient I supply, and a shortage of retinene results in so-called night blindness.

Animals Eye

Almost all animals can perceive and respond to light, but eyes are as varied as the animals that posses them.

Eyes that form definite images are found only in some mollusks, mainly squids, octopuses and cuttlefish; in a few worm; in most arthropods, including insects, spiders, lobster, and most crabs; and in vertebrates. Except for most insects, these animals have eyes that are similar in structure and function to a camera. The eye uses a single Lens to focus a picture on a surface of densely packed cells called photoreceptors. The receptor surface, called the retina, functions like a piece of film. An external object is pictured on the retina like the points of newspaper photograph. The picture later received in the Brain, however is not the same simple point by point image. Exactly what this picture is remains unknown, but perception is a process that takes place in the brain not in the eye. Information from the eye, like the piece of a puzzle, is analyzed in the brain and fitted into meaningful forms.

Most insect eyes are built on an entirely different principle from the described above and are called compound eyes. Thousands of densely packed lenses are spread like a honeycomb over a spherical surface so that a mosaic image is formed. Each lens is associated with relatively few receptor cells, and the entire unit is called an ommatidium. No structure, therefore, is strictly analogous to the retina of other animals. What kind of image this arrangement conveys to the insect depends on the complexity of the structure.