These cells are termed photoreceptors and the two distinct types of cells are the rods and cones. The retina has two types of cells that initiate these chemical reactions. Visual association areas of the brain further process the signals to make them understandable within the correct context. These chemical reactions cause electrical signals, which are transmitted through nerve cells into the optic nerve, which carries these signals to the brain, where the electrical signals are converted into recognizable images. When focused light strikes the retina, chemical reactions occur within specialized layers of cells. The retina acts like the film in a camera to create an image. This occurs under reduced illumination or in darkness. When these muscles contract, the pupil dilates (becomes larger). The second set of muscle fibers radiate outward from the pupil. The iris has a ring of muscle fibers around the pupil, which, when they contract, causes the pupil to constrict (become smaller). The iris is a ring-shaped tissue with a central opening, which is called the pupil. The iris, which is the colored part of the eye, controls the amount of light that enters the eye. If one wears contact lenses, the contact lens rests on the cornea. The main purpose of the cornea is to help focus light as it enters the eye. The cornea is located just in front of the iris, which is the colored part of the eye. In fact, the cornea is so clear that one may not even realize it is there. CorneaThe cornea is the transparent, clear layer at the front and center of the eye. The eye is composed of various parts, all of which work together to allow the sight to occur. SLIDESHOW Pink Eye (Conjunctivitis) Symptoms, Causes, Treatments See Slideshow If the aqueous humor cannot properly drain out of the eye, the pressure can build up inside the eye, causing optic nerve damage and eventually vision loss, a condition known as glaucoma. The trabecular meshwork is important because it is the area where the aqueous humor drains out of the eye. The anterior chamber angle and the trabecular meshwork are located where the cornea meets the iris. Anterior Chamber Angle and Trabecular Meshwork
The aqueous humor helps to nourish the cornea and the lens.Īnterior Chamber Angle and the Trabecular Meshwork
The fluid that fills this chamber is called the aqueous humor. The anterior chamber is the fluid-filled space immediately behind the cornea and in front of the iris. The tears drain away from the eye through the nasolacrimal duct, which is located at the inner corner of the eye. The lacrimal gland produces tears that help lubricate and moisten the eye, as well as flush away any foreign matter that may enter the eye. The orbit also contains the lacrimal gland that is located underneath the outer portion of the upper eyelid. In addition to the eyeball itself, the orbit contains the muscles that move the eye, blood vessels, and nerves. The eye is cushioned within the orbit by pads of fat. The orbit is formed by the cheekbone, the forehead, the temple, and the side of the nose. The orbit is the bony eye socket of the skull. Just as a camera focuses light onto the film to create a picture, the eye focuses light onto a specialized layer of cells, called the retina, to produce an image. Each gathers light and then transforms that light into a "picture." Both also have lenses to focus the incoming light. More than 75% of the information we receive about the world around us consists of visual information.
Vision is by far the most used of the five senses and is one of the primary means that we use to gather information from our surroundings. Although the eye is small, only about 1 inch in diameter, each part plays an important role in allowing people to see the world.