The eye is an organ that has been formed to detect light. The simplest eyes only serves to detect whether light or dark environment. Eyes of a more complicated function to give sense of sight.The types of eye
Eyes are among the arthropod groups (insects and the like), and consists of many angles to give pixels (instead of multiple images as is often said).
Some animals also have oselus (simple eye or eyes that there is a point on the lower level animals). For example, snail points only to distinguish the light or not (day and night), but can not see whether the object is in front of him.
In most vertebrates and some mollusks the eye acts to transmit images on the retina that is sensitive to light, where light is detected and transmitted to the brain via the optic nerve. Points are usually nearly spherical shape, containing materials such as optically clear gel called gelemaca, with the lens focus and muscle called the iris that controls the rate of the incoming light. This iris controls the pupil opening (pupil), the black circle in the middle of the color in the eye.
The structure of the human eye depends on its ability to focus light on the retina. Each component of the path traveled by light is transparent to reduce the dim light. Cornea and lens to concentrate the incoming light on the retina, which activates a chemical reaction and generate signals for transmission to the brain.Light coming from outside will pass through the cornea and lens before reaching gelemair. Gelemair helps maintain the convex shape and moisten the cornea. Iris (color) is located in front of the lens pupil aperture control. Further light will go through before reaching the groove gelemaca fovea in the retina. This is where many of the cells is sensitive to light. Light from a distant object and light from objects near the focus.
So that light can be focused, the light must be refracted. Rates of refraction depends on the distance of the object being viewed. Remote object requires less refraction of light from nearby objects. Most of the refraction occurs at the cornea which has a permanent bend. Other necessary refractive lenses occur. Flat lens can be pulled by the muscles, the correct lens power. When a person ages, he will lose the ability to correct the focus. This is known as presbyopia.
