Anatomy of the Eye
Although small in size, the eyes are one of the most complex organs in the human body. They act similar to a video camera, transferring the images you see to the brain for processing and storage. Light enters the eye and goes through the cornea, a transparent, thick layer that protects the surface of the eye. The light rays then travel through the pupil – the black circle found in the middle of the eye – and through the lens. As the light passes through the pupil, a muscle known as the iris (colored ring) causes the diameter of the pupil to change in size as the light changes. Too much light will cause the pupil to shrink in order to limit light rays from entering. With too little light, the pupil will enlarge, or dilate, to allow more light rays in. The lens is behind the pupil and is used to focus the images seen by the eye. This is done through a jell-type material known as the vitreous humor and continues to the back of the eye, or retina.
Optometry is the specialized health care profession that deals with eyes and related structures, as well as vision systems and vision information processing in humans. Doctors of optometry aid in the examination, diagnosis and treatment of various disorders and diseases associated with the eye. An optometrist is licensed to conduct eye exams, manage eye conditions and diseases and prescribe corrective glasses and contact lenses. They may also help patients through vision therapy to treat abnormalities of the eyes, prescribe drugs for the eyes or send patients to an ophthalmologist for surgery if required. Many individuals do not have perfect vision. Individuals who are able to see up close but not far away are nearsighted. This occurs when light rays entering the eye focus on a certain point towards the front of the retina. Individuals who can see far away but not close up are farsighted. This happens when light rays entering the eye focus on a certain point towards the back of the retina. With both conditions, glasses and contact lenses can make seeing more crisp and clear.
The human eye is made up of several parts that work together to perform a wide range of functions. Some of these parts include the cornea, sclera, iris, lens, pupil, vitreous, retina, humor and optic nerve. The cornea is the outer covering that lies over the center of the eye. As light enters the eye through the cornea, the shape of the cornea works like a lens to refract light towards a focal point at the back of the eye. Sclera is the white part of the eye that gives the eye protection and strength. The iris is the colored part of the eye, expanding or contracting around the pupil. The pupil manages light entering the eye with the help of the muscles of the iris. The lens of the eye is flexible, allowing the eye to change the focal length and thus, the focal point of the light that passes through it. The vitreous humor gives the eye its firmness and shape. Within the vitreous are small lumps known as "floaters" that appear to float before or in front of the eye in some individuals. The retina is made up of nerve tissue that lines the rear wall of the eye. It receives impulses that translate images to the brain. The optic nerve serves as the conductor, transmitting electrical impulses from the retina back to the brain. This is the final stage of the vision process.
Individuals interested in learning more about the human eye, how it functions and its parts in detail can review the resources below. The following resources are eye anatomy sites that include virtual dissections, animations, simulations, lessons, videos and more.