The different parts of the eye permit the body to take in light and perceive objects around us in the proper color, information and depth. The eye is likewise greatly included with the nerve system, which permits the brain to take in information from the eyes and make the proper choices on how to act on this info. The light-sensitive biochemical in rods is called rhodopsin or visual purple. The spaces within the eye are filled with fluids that help maintain its shape. The convex surface of the lens and, to a lesser extent, the surfaces of the fluids in the chambers of the eye then refract the light again. Many strong but delicate fibers, called suspensory ligaments, extend inward from the ciliary processes and hold the transparent lens in position. The cornea also allows the eye to properly focus on light more effectively. It is filled with a transparent, jellylike fluid called vitreous humor, which along with collagen fibers forms the vitreous body. The inner layer of the wall of the eye consists of the retina, which contains the visual receptor cells (photoreceptors). The retina contains two cells which help its function called cones and rods. The suspensory ligaments attached to the margin of the capsule are also under tension. The lacrimal glands have about 10 excretory ducts that carry fluid out of the glandular substance onto the outer surface of the eyeball. External components include structures which can be seen on the exterior of the eye, and internal components include structures present within. The ciliary muscle controls the actions of the suspensory ligaments in accommodation. The three types of cones each contain one of these three photopigments. Most of the nerve supply to the eye, both motor and sensory, are via the cranial nerves. Table 1. Consequently, to view something in detail, a person moves the eyes so that the important part of an image falls on the fovea centralis. Basically, the role of the eye is to convert light into electrical signals called nerve impulses that the brain converts into images of our surroundings. These proteins, along with the absence of organelles that scatter light (mitochondria, endoplasmic reticula, and nuclei), account for the transparency of the lens. Optic nerve – a bundle of more than one million nerve fibres that carries visual messages from the retina to the brain. The ciliary muscle and suspensory ligaments, along with the structure of the lens itself, enable the lens to adjust shape to facilitate focusing, a phenomenon called accommodation. This gel takes in nutrients from the ciliary body, aqueous humor and the retinal vessels so the eye can remain healthy. This area surrounds the pupil, and uses the dilator pupillae muscles to broaden or close the student. This happens at the curved surface between the air and the cornea and at the curved surfaces of the lens itself. Lens – the clear part of the eye behind the iris that helps to focus light, or an image, onto the retina.

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