Characteristics Of The Eye

Summary ch.25.1

Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement. In higher organisms the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. The eye has many parts that support its health but the important components that help with visual acuity is Cornea which is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. The cornea, with the anterior chamber and lens, refracts light. Then comes the Pupil is the hole located in the center of the iris of the eye that allows light to enter the retina. Iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupils and thus the amount of light reaching the retina. The crystalline lens is a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. The lens, by changing shape, functions to change the focal distance of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina. This adjustment of the lens is known as accommodation. The retina is a light-sensitive tissue lining the inner surface of the eye. Finally the optic nerve, also known as cranial nerve 2,transmits visual information from the retina to the brain.Now the process which the eye translate light first Light travels into the cornea ,then into the pupil which can be adjusted by the ciliary muscles of the iris (the iris can adjust light from 2mm to 8mm in diameter), After the amount of light entering has been adjusted by the iris the Crystalline lens (which is a converging lens) will receives the light and again adjust the image again by growing in length to adjust the focal length (accommodation) ,Then after the retina will receive an inverted image that will be process through the use of photosensitive cones and rods on the retina * Cones-distinguish frequency ranges but required brighter lights (color vision) and are located central region of the retina * Rods-rods are not color sensitive they are responsible for our dark adapted or scotopic vision (night vision)
, and finally this information is sent via the optic nerve to the visual cortex and produces a right side up image. The eye has image distant that is constant and the focus length varies (though change of the ciliary muscles

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