In order to begin our detailed description of eye care careers, it would be helpful to understand the language of the visual sciences. In eye care, as in other health care fields, there are professionals who specialize in the study and treatment of one disease, like glaucoma or strabismus, and there are those who limit their practice to one part of the eye, such as the retina. To the non expert, these words may be as difficult to say, spell, and pronounce as a foreign language. For the practicing eye care specialist, medical terminology is a communication tool that is universally understood by others in the field.
Medical terminology should not be a foreign language to anyone. It is the language that well-informed health care consumers should master so that they can converse with their care providers. Everyone can benefit from taking the time to learn more about the technical aspects of visual health.
Students who are preparing for careers in the ophthalmic sciences learn about the parts of the eye and visual system in courses called "Anatomy and Physiology." In order to adequately care for patients, eye care professionals—regardless of their scope of practice—must have a clear understanding of how the eye functions.
The Eye
The eye is surrounded by a cone-shaped socket called the orbit. Fatty tissue lines the orbit, forming a cushion for the eyeball, and six muscles move the eye. These muscles operate much like puppet strings.
The brow, upper and lower eyelids, and eyelashes protect the eyeball from dust and foreign objects. The conjunctiva—a mucous membrane—lines the inside of the eyelids and continues over the forepart of the eyeball. As we blink, mucus and tears from the lacrimal glands are distributed over the eye to keep it moist.
There are three layers of tissue that form the wall of the eyeball. The sclera and cornea form the outside layer. The sclera is the ''white of the eye" that covers almost the entire visible eye. The cornea is the transparent shield that enables light rays to enter the eye.
The main part of the middle layer of the wall—or uveal tract—is the colored iris. Whether your eyes are blue, green, hazel, or brown depends on the amount of melanin—a light-absorbing pigment—they have. Blue-eyed people have less of this brownish-black substance than brown-eyed people do. The black disk inside the iris is the pupil, which can be dilated by two muscles when looking at far objects. The ciliary body encircles the iris and serves two functions. It adjusts the lens behind the cornea to create crisp images, and it produces the clear, watery fluid that lubricates the cornea and lens. The back layer of the uveal tract is the choroid, a blood-vessel-laden tissue that nourishes the retina.
The retina is the very fragile interior wall of the eyeball. Light-sensitive retinal cells—called rods and cones—change light into electrical signals. It is the macula at the center of the retina that produces the sharp images that we see while looking directly at an object. The rest of the retina assists with peripheral vision and seeing shades of gray and colors. Nerve fibers join the rods and cones to the optic nerve at the base of the retina. Electrical impulses from the retina are cabled to the brain, which interprets the visual images. Approximately one-third of the brain is involved in the processing of visual signals and information. This activity is conducted constantly during waking hours and continues to some extent during sleep, particularly during the active dreaming periods of sleep.
Most of the interior of the eyeball is filled with the vitreous humor, a clear jellylike mass. Like the air in a basketball, the vitreous humor maintains the shape and pressure within the eyeball.
