Macular Degeneration Glossary of Terms

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20/20: See; Twenty-twenty.

Abnormal: Not normal. Deviating from the usual structure, position, condition, or behavior. In referring to a growth, abnormal may mean that it is cancerous or premalignant (likely to become cancer).

Acetate: A molecular ion derived from acetic acid. The formula of acetate is CH3COO-.

Age-related macular degeneration: An eye disease with its onset usually after age 60 that progressively destroys the macula, the central portion of the retina, impairing central vision. Age-related macular degeneration (AMD) rarely causes blindness because only the center of vision is affected. However, injury to the macula in the center of the retina can impair the ability to see straight ahead clearly and sometimes make it difficult to read, drive, or perform other daily activities that require fine central vision.
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Aging: The process of becoming older, a process that is genetically determined and environmentally modulated.
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Amsler grid: While conducting an eye examination, the eye care professional may ask the patient to look at an Amsler grid. This grid is a pattern that resembles a checkerboard. The patient covers one eye and stares at a black dot in the center of the grid. While staring at the dot, the patient may notice that the straight lines in the pattern appear wavy.

Analogous: In anatomy, similar in appearance or function but otherwise different. Two structures may be analogous if they serve the same purpose but differ evolutionary in origin as, for example, human and insect legs. As compared to homologous.

Angiogram: An x-ray of blood vessels which can be seen because the patient receives an injection of dye to outline the vessels on the x-ray.

Angiography: A procedure performed to view blood vessels after injecting them with a radioopaque dye that outlines them on x-ray. This technique can be usefully used to look at arteries in many areas of the body, including the brain, neck (carotids), heart, aorta, chest, pulmonary circuit, kidneys, gastrointestinal tract, and limbs.

Antibody: An immunoglobulin, a specialized immune protein, produced because of the introduction of an antigen into the body, and which possesses the remarkable ability to combine with the very antigen that triggered its production.
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Antioxidant: Any substance that reduces oxidative damage (damage due to oxygen) such as that caused by free radicals. Free radicals are highly reactive chemicals that attack molecules by capturing electrons and thus modifying chemical structures.
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Apnea: An apnea is a period of time during which breathing stops or is markedly reduced. There are two types of apneas, the more common obstructive sleep apnea and the less common central sleep apnea.
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Argon laser: A laser with ionized argon as the active medium. Argon lasers are used for photocoagulation in ophthalmology.

ARMD: Age-related macular degeneration (which may also be abbreviated as AMD).

Aspirin: A good example of a tradename that entered into the language, Aspirin was once the Bayer trademark for acetylsalicylic acid.
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Atorvastatin: A medication that lowers the level of cholesterol in the blood. Atorvastatin is a statin drug. All statins prevent the production of cholesterol in the liver by blocking the enzyme that makes cholesterol, HMGCoA reductase. They lower total blood cholesterol as well as low-density lipoprotein (LDL) cholesterol levels. Lowering LDL cholesterol levels retards progression and may even reverse coronary artery disease. Unlike the other statins, atorvastatin can also reduce the concentration of triglycerides in the blood. (High blood concentrations of triglycerides have been associated with coronary artery disease.) The brand name of atorvastin is Lipitor.

Atrophy: Wasting away or diminution. Muscle atrophy is wasting of muscle, decrease in muscle mass.
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Avastin: The first drug in a class designed to treat cancer by compromising its blood supply. Avastin (bevacizumab) is believed to prevent angiogenesis, the formation of new blood vessels that supply the tumor with blood, oxygen and other nutrients and allow the tumor to grow and metastasize to other sites in the body. Additionally, Avastin may interfere with tumor growth by causing blood vessels to shrink away from a tumor.
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Beta carotene: A vitamin that acts as an antioxidant, protecting cells against oxidation damage. Beta carotene is converted by the body to vitamin A. Food sources of beta carotene include vegetables such as carrots, sweet potatoes, spinach and other leafy green vegetables; and fruit such as cantaloupes and apricots. Excessive carotene in the diet can color the skin yellow, a condition called carotenemia. Carotenemia is sometimes seen in infants fed too many mashed carrots and is a reversible condition. Beta carotene supplements have been found not to reduce the risks for cancer or heart disease.

Bevacizumab: Generic name for a monoclonal antibody anticancer drug. See: Avastin.

Bilateral: Having, or relating to, two sides. Bilateral is as opposed, for example, to unilateral (which means having, or relating to, one side).

Blind: 1. Unable to see. Without part or all of the sense of sight.
2. In a clinical trial, not to know the treatment given or received. The participant is not told whether they are in the experimental or control arm of the study. Also called masked.

Blindness: Loss of useful sight. Blindness can be temporary or permanent. Damage to any portion of the eye, the optic nerve, or the area of the brain responsible for vision can lead to blindness. There are numerous (actually, innumerable) causes of blindness. The current politically correct terms for blindness include visually handicapped and visually challenged.

Brain: That part of the central nervous system that is located within the cranium (skull). The brain functions as the primary receiver, organizer and distributor of information for the body. It has two (right and left) halves called "hemispheres."

Cancer: An abnormal growth of cells which tend to proliferate in an uncontrolled way and, in some cases, to metastasize (spread).
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Cataract: A clouding or loss of transparency of the lens in the eye as a result of tissue breakdown and protein clumping. There are many causes of cataracts, including aging, cortisone medication, trauma, diabetes, and other diseases. Cataracts affect most people who live into an old age. Symptoms include double or blurred vision and sensitivity to light and glare. A physician can diagnose cataracts by examining the eyes with a viewing instrument. Sunglasses can help to prevent cataracts.
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Cataract surgery: Removal of the clouded lens (the cataract) in its entirety by surgery, usually followed by replacement of the lens with an intraocular lens (IOL) made of plastic, silicone, acrylic or other material. The operation typically takes about an hour, is done under local anesthetic only, and does not require hospitalization.

Central vision: Straight-ahead vision. Central vision is the work of the macula, a small area in the center of the retina that contains a rich collection of cones. (The retina is made up of two types of cells, the cones and the rods. Millions of cones are packed into the macula. The cones are nerve cells sensitive to light, fine detail, and color.) Central vision permits a person to read, drive, and perform other activities that require fine, sharp, straight-ahead vision. As opposed to peripheral vision.

Choroid: In the eye, a thin vascular layer between the sclera and the retina. The choroid supplies blood to the retina and conducts arteries and nerves to other structures in the eye.

Clinical trials: Trials to evaluate the effectiveness and safety of medications or medical devices by monitoring their effects on large groups of people.
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Colon: The part of the large intestine that runs from the cecum to the rectum as a long hollow tube that serves to remove water from digested food and let the remaining material, solid waste called stool, move through it to the rectum and leave the body through the anus. .
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Contrast: Short for "contrast media." Contrast media are X-ray dyes used to provide contrast, for example, between blood vessels and other tissue.

Cornea: The clear front window of the eye that transmits and focuses light into the eye.
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Cure: 1. To heal, to make well, to restore to good health. Cures are easy to claim and, all too often, difficult to confirm.
2. A time without recurrence of a disease so that the risk of recurrence is small, as in the 5-year cure rate for malignant melanoma.
3. Particularly in the past, a course of treatment. For example, take a cure at a spa.
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Diabetic retinopathy: A common complication of diabetes affecting the blood vessels in the retina (the thin light-sensitive membrane that covers the back of the eye). If untreated, it may lead to blindness. If diagnosed and treated promptly, blindness is usually preventable.
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Diagnosis: 1 The nature of a disease; the identification of an illness. 2 A conclusion or decision reached by diagnosis. The diagnosis is rabies. 3 The identification of any problem. The diagnosis was a plugged IV.
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Drusen: Tiny yellow or white deposits in the retina of the eye or on the optic nerve head.
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Dry eye: A deficiency of tears. The main symptom is usually a scratchy or sandy feeling as if something is in the eye. Other symptoms may include stinging or burning of the eye; episodes of excess tearing that follow periods of very dry sensation; a stringy discharge from the eye; and pain and redness of the eye. Sometimes people with dry eye experience heaviness of the eyelids or blurred, changing, or decreased vision, although loss of vision is uncommon.
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Ear: The hearing organ. There are three sections of the ear, according to the anatomy textbooks. They are the outer ear (the part we see along the sides of our head behind the temples), the middle ear, and the inner ear. But in terms of function, the ear has four parts: those three and the brain. Hearing thus involves all parts of the ear as well as the auditory cortex of the brain. The external ear helps concentrate the vibrations of air on the ear drum and make it vibrate. These vibrations are transmitted by a chain of little bones in the middle ear to the inner ear. There they stimulate the fibers of the auditory nerve to transmit impulses to the brain.
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Edema: The swelling of soft tissues as a result of excess water accumulation.
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Emergency department: The department of a hospital responsible for the provision of medical and surgical care to patients arriving at the hospital in need of immediate care. Emergency department personnel may also respond to certain situations within the hospital such cardiac arrests.
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Endothelial: Relating to the endothelium, the layer of flat cells lining the closed spaces of the body such as the inside of blood vessels, lymphatic vessels, the heart, and body cavities.
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Epithelium: The outside layer of cells that covers all the free, open surfaces of the body including the skin, and mucous membranes that communicate with the outside of the body. By contrast the endothelium is the layer of cells lining the closed internal spaces of the body such as the blood vessels and lymphatic vessels (that convey the lymph, a milky fluid).

Essential: 1. Something that cannot be done without.
2. Required in the diet, because the body cannot make it. As in an essential amino acid or an essential fatty acid.
3. Idiopathic. As in essential hypertension. "Essential" is a hallowed term meaning "We don't know the cause."

Etiology: The study of the causes. For example, of a disorder.
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Family history: The family structure and relationships within the family, including information about diseases in family members.
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FDA: The Food and Drug Administration, an agency within the U.S. Public Health Service, which is a part of the Department of Health and Human Services.
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Fluorescein angiography: A test to examine blood vessels in the retina, choroid, and iris of the eye. A special dye is injected into a vein in the arm and pictures are taken as the dye passes through the blood vessels in the eye.
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Food and Drug Administration: The FDA, an agency within the U.S. Public Health Service, which is a part of the Department of Health and Human Services.
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Genes: The basic biological units of heredity. Segments of deoxyribonucleic acid (DNA) needed to contribute to a function.
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Genetic: Having to do with genes and genetic information.

Glaucoma: A common eye condition in which the fluid pressure inside the eyes rises because of slowed fluid drainage from the eye. If untreated, it may damage the optic nerve and other parts of the eye, causing the loss of vision or even blindness.
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Heart: The muscle that pumps blood received from veins into arteries throughout the body. It is positioned in the chest behind the sternum (breastbone; in front of the trachea, esophagus, and aorta; and above the diaphragm muscle that separates the chest and abdominal cavities. The normal heart is about the size of a closed fist, and weighs about 10.5 ounces. It is cone-shaped, with the point of the cone pointing down to the left. Two-thirds of the heart lies in the left side of the chest with the balance in the right chest.
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Heart attack: The death of heart muscle due to the loss of blood supply. The loss of blood supply is usually caused by a complete blockage of a coronary artery, one of the arteries that supplies blood to the heart muscle. Death of the heart muscle, in turn, causes chest pain and electrical instability of the heart muscle tissue.
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Hemorrhagic: Pertaining to bleeding or the abnormal flow of blood.
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In vivo: In the living organism, as opposed to in vitro (in the laboratory).

Indicate: In medicine, to make a treatment or procedure advisable because of a particular condition or circumstance. For example, certain medications are indicated for the treatment of hypertension during pregnancy while others are contraindicated.

Inflammation: A basic way in which the body reacts to infection, irritation or other injury, the key feature being redness, warmth, swelling and pain. Inflammation is now recognized as a type of nonspecific immune response.
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Intervention: The act of intervening, interfering or interceding with the intent of modifying the outcome. In medicine, an intervention is usually undertaken to help treat or cure a condition. For example, early intervention may help children with autism to speak. "Acupuncture as a therapeutic intervention is widely practiced in the United States," according to the National Institutes of Health. From the Latin intervenire, to come between.

Intraocular: In the eye. The intraocular pressure is the pressure within the eye.

Iris: The iris is the circular, colored curtain of the eye. Its opening forms the pupil. The iris helps regulate the amount of light that enters the eye.
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Laser: A powerful beam of light that can produce intense heat when focused at close range. Lasers are used in medicine in microsurgery, cauterization, for diagnostic purposes, etc. For example, lasers are employed in microsurgery to cut tissue and remove tissue.
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Legal blindness: The criteria used to determine eligibility for government disability benefits and which do not necessarily indicate a person's ability to function.
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Lipitor: See: Atorvastatin.

Macula: A macula is a small spot. A macula on the skin is a small flat spot while the macula in the eye is a small spot where vision is keenest in the retina.

Macular: Pertaining to the macula. A macula is a small spot. A macula on the skin is a small flat spot while the macula in the eye is a small spot where vision is keenest in the retina.

Macular degeneration: A disease that progressively destroys the macula, the central portion of the retina, impairing central vision. Macular degeneration rarely causes blindness because only the center of vision is affected. However, injury to the macula in the center of the retina can impair the ability to see straight ahead clearly and sometimes make it difficult to read, drive, or perform other daily activities that require fine central vision.
See the entire definition of Macular degeneration

Maculopathy: Any pathologic condition or disease of the macula, the small spot in the retina where vision is keenest. Also called macular retinopathy.

Medical school: A school with a curriculum leading to a medical degree. The mission of every medical school includes medical teaching, research, and patient care. All medical schools share the goal of preparing students in the art and science of medicine, and providing them with the background necessary to enter the period of graduate medical education. The years of medical school preceding graduate medical education are typically divided into a preclinical phase and a clinical phase.
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Membrane: A very thin layer of tissue that covers a surface.

Metabolic: Relating to metabolism, the whole range of biochemical processes that occur within us (or any living organism). Metabolism consists of anabolism (the buildup of substances) and catabolism (the breakdown of substances).
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Metabolic syndrome: A constellation of conditions that place people at high risk for coronary artery disease. These conditions include type 2 diabetes, obesity, high blood pressure, and a poor lipid profile with elevated LDL ("bad") cholesterol, low HDL ("good") cholesterol, elevated triglycerides. All of these conditions are associated with high blood insulin levels. The fundamental defect in the metabolic syndrome is insulin resistance in both adipose tissue and muscle. Drugs that decrease insulin resistance also usually lower blood pressure and improve the lipid profile.
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Molecule: The smallest unit of a substance that can exist alone and retain the character of that substance.

Myopia: Nearsightedness, the ability to see close objects more clearly than distant objects.
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Nerve: A bundle of fibers that uses chemical and electrical signals to transmit sensory and motor information from one body part to another. See: Nervous system.

NIH: The National Institutes of Health. The NIH is an important U.S. health agency. It is devoted to medical research. Administratively under the Department of Health and Human Services (HHS), the NIH consists of 20-some separate Institutes and Centers. NIH's program activities are represented by these Institutes and Centers.
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Obesity: The state of being well above one's normal weight.
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Occult: Hidden.
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Ocular: Having to do with the eye.
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Ophthalmic: Pertaining to the eye. An ophthalmic ointment is designed for the eye.

Ophthalmologist: An eye doctor. A physician practicing ophthalmology. An ophthalmologist is an M.D.

Ophthalmology: The art and science of eye medicine.

Ophthalmoscope: A lighted instrument, one of the most important tools of the physician, used to examine the interior of the eye, including the lens, retina and optic nerve.
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Optic: Having to do with vision.

Optic nerve: The optic nerve connects the eye to the brain. The optic nerve carries the impulses formed by the retina, the nerve layer that lines the back of the eye and senses light and creates impulses. These impulses are dispatched through the optic nerve to the brain, which interprets them as images. Using an ophthalmoscope, the head of the optic nerve can be easily seen. It can be viewed as the only visible part of the brain (or extension of it).
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Optometrist: A health care professional who is licensed to provide primary eye care services:

• to examine and diagnose eye diseases such as glaucoma, cataracts, and retinal diseases and, in certain states in the U.S., to treat them;
• to diagnose related systemic (bodywide) conditions such as hypertension and diabetes that may affect the eyes;
• to examine, diagnose and treat visual conditions such as nearsightedness, farsightedness, astigmatism and presbyopia; and
• to prescribe glasses, contact lenses, low vision rehabilitation and medications as well as perform minor surgical procedures such as the removal of foreign bodies.

Osteoporosis: Thinning of the bones with reduction in bone mass due to depletion of calcium and bone protein. Osteoporosis predisposes a person to fractures, which are often slow to heal and heal poorly. It is more common in older adults, particularly post-menopausal women; in patients on steroids; and in those who take steroidal drugs. Unchecked osteoporosis can lead to changes in posture, physical abnormality (particularly the form of hunched back known colloquially as "dowager's hump"), and decreased mobility.
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Oxygen: A colorless, odorless and tasteless gas that makes up about 20% of the air we breathe (and at least half the weight of the entire solid crust of the earth) and which combines with most of the other elements to form oxides. Oxygen is essential to human, animal and plant life.
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Pain: An unpleasant sensation that can range from mild, localized discomfort to agony. Pain has both physical and emotional components. The physical part of pain results from nerve stimulation. Pain may be contained to a discrete area, as in an injury, or it can be more diffuse, as in disorders like fibromyalgia. Pain is mediated by specific nerve fibers that carry the pain impulses to the brain where their conscious appreciation may be modified by many factors.
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Pathologic: 1. Indicative of or caused by disease, as in a pathologic fracture, pathologic tissue, or pathologic process. 2. Pertaining to pathology, the branch of medicine that studies disease and especially the essential nature of disease.

Peripheral: Situated away from the center, as opposed to centrally located.
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Peripheral vision: Side vision. The ability to see objects and movement outside of the direct line of vision. Peripheral vision is the work of the rods, nerve cells located largely outside the macula (the center) of the retina. The rods are also responsible for night vision and low-light vision but are insensitive to color. As opposed to central vision.

Periphery: 1. The outside or surface of a structure; the portion outside the central region.
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Pharmacy: A location where prescription drugs are sold. A pharmacy is, by law, constantly supervised by a licensed pharmacist.

Photodynamic therapy: A form of cancer treatment using an photosensitizing agent administered intravenously which concentrates selectively in tumor cells, followed by exposure of the tumor tissue to a special red laser light, in order to destroy as much of the tumor as possible.
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Pigment: A substance that gives color to tissue. Pigments are responsible for the color of skin, eyes, and hair.

Pigmentation: The coloring of the skin, hair, mucous membranes, and retina of the eye.
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Pons: A specific section of the brain formed by the rounded prominence on the front surface of the brainstem. (The brainstem is the lowest part of the brain that merges with the spinal cord; it consists of a structure called the medulla oblongata, the midbrain and the pons.) Cranial nerves V, VI, VII and VIII take origin at the border of the pons.
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Posterior: The back or behind, as opposed to the anterior.
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Predispose: To make more likely or render susceptible. Smoking predisposes to a number of diseases, including esophageal cancer.

Prognosis: 1. The expected course of a disease.
2. The patient's chance of recovery.
The prognosis predicts the outcome of a disease and therefore the future for the patient. His prognosis is grim, for example, while hers is good.
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Progressive: Increasing in scope or severity. Advancing. Going forward. In medicine, a disease that is progressive is going from bad to worse.

Prospective: Looking forward. A prospective study or a prospective clinical trial is one in which the participants are identified and then followed forward in time.

Proteins: Large molecules composed of one or more chains of amino acids in a specific order determined by the base sequence of nucleotides in the DNA coding for the protein.
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Quality of life: An important consideration in medical care, quality of life refers to the patient's ability to enjoy normal life activities. Some medical treatments can seriously impair quality of life without providing appreciable benefit, while others greatly enhance quality of life.

Randomized: The use of chance alone to assign the participants in an experiment or trial to different groups in order to fairly compare the outcomes with different treatments. Randomization is an important feature of experimental design.

Rectum: The last 6 to 8 inches of the large intestine. The rectum stores solid waste until it leaves the body through the anus. The word rectum comes from the Latin rectus meaning straight (which the human rectum is not).

Retina: The retina is the nerve layer that lines the back of the eye, senses light, and creates impulses that travel through the optic nerve to the brain. There is a small area, called the macula, in the retina that contains special light-sensitive cells. The macula allows us to see fine details clearly.
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Retinal: Pertaining to the retina, the extraordinary layer of neurons (nerve cells) that line the back of the eye, which can sense light and create impulses capable of voyaging through the optic nerve to the brain where the impulses are recognized as an image.
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Retinal disease: In medicine, called retinopathy. See: Retinopathy.

Retinal pigment epithelium: The pigment cell layer that nourishes the retinal cells.
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Retinopathy: Any disease of the retina, the light-sensitive membrane at the back of the eye. The type of retinopathy is often specified. Arteriosclerotic retinopathy is retinal disease due to arteriosclerosis ("hardening of the arteries"). Diabetic retinopathy is retinal disease associated with diabetes. Hypertensive retinopathy is retinal disease due to high blood pressure. Etc.

Risk factor: Something that increases a person's chances of developing a disease.

Selenium: An essential trace mineral that functions largely in the form of proteins, called selenoproteins, which act as enzymes and help prevent damage to cells in the body by oxidants in the environment or those produced by normal metabolism.
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Senile: 1. Pertaining to old age. 2. Pertaining to the physical decline associated with old age. 3. Pertaining to the mental decline once associated with old age but now known to be due to dementia, such as Alzheimer's disease or cerebral atherosclerosis. "The road to senility is paved with plaques." (Paul F. Wehrle, MD [1921-2004] pediatrician and vaccine researcher)
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Sensitivity: 1. In psychology, the quality of being sensitive. As, for example, sensitivity training, training in small groups to develop a sensitive awareness and understanding of oneself and of ones relationships with others. 2. In disease epidemiology, the ability of a system to detect epidemics and other changes in disease occurrence. 3. In screening for a disease, the proportion of persons with the disease who are correctly identified by a screening test. 4. In the definition of a disease, the proportion of persons with the disease who are correctly identified by defined criteria.

Sensory: Relating to sensation, to the perception of a stimulus and the voyage made by incoming (afferent) nerve impulses from the sense organs to the nerve centers.
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Sleep: The body's rest cycle.
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Sleep apnea: The temporary stoppage of breathing during sleep, often resulting in daytime sleepiness. Apnea is a Greek word that means "want of breath."
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Steroid: A general class of chemical substances that are structurally related to one another and share the same chemical skeleton (a tetracyclic cyclopenta[a]phenanthrene skeleton).
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Stroke: The sudden death of some brain cells due to a lack of oxygen when the blood flow to the brain is impaired by blockage or rupture of an artery to the brain. A stroke is also called a cerebrovascular accident or, for short, a CVA.
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Surgery: The word "surgery" has multiple meanings. It is the branch of medicine concerned with diseases and conditions which require or are amenable to operative procedures. Surgery is the work done by a surgeon. By analogy, the work of an editor wielding his pen as a scalpel is s form of surgery. A surgery in England (and some other countries) is a physician's or dentist's office.
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Syndrome: A set of signs and symptoms that tend to occur together and which reflect the presence of a particular disease or an increased chance of developing a particular disease.
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Syndrome X: See: Metabolic syndrome.

Systemic: Affecting the entire body. A systemic disease such as diabetes can affect the whole body. Systemic chemotherapy employs drugs that travel through the bloodstream and reach and affect cells all over the body.

Therapy: The treatment of disease.
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Tomography: The process for generating a tomogram, a two-dimensional image of a slice or section through a three-dimensional object. Tomography achieves this remarkable result by simply moving an x-ray source in one direction as the x-ray film is moved in the opposite direction during the exposure to sharpen structures in the focal plane, while structures in other planes appear blurred. The tomogram is the picture; the tomograph is the apparatus; and tomography is the process.
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Topical: Pertaining to a particular surface area. A topical agent is applied to a certain area of the skin and is intended to affect only the area to which it is applied. Whether its effects are indeed limited to that area depends upon whether the agent stays where it is put or is absorbed into the blood stream.

Uveitis: Inflammation of the uvea, the part of the eye that collectively refers to the iris, the choroid of the eye, and the ciliary body. The uvea provides most of the blood supply to the retina. Uveitis as a rule signifies inflammation involving the iris, choroid, and ciliary body -- all three components of the uveal tract.
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Vascular: Relating to the blood vessels of the body. The blood vessels of the body, as a group, are referred to as the vascular system.
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VEGF: Vascular endothelial growth factor, a substance made by cells that stimulates the formation of new blood vessels, a process called angiogenesis. VEGF also acts as a mitogen for vascular endothelial (vessel lining) cells, stimulating these cells to divide and multiply.
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Vein: A blood vessel that carries blood low in oxygen content from the body back to the heart. The deoxygenated form of hemoglobin (deoxyhemoglobin) in venous blood makes it appear dark. Veins are part of the afferent wing of the circulatory system which returns blood to the heart.
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Vessel: A tube in the body that carries fluids: blood vessels or lymph vessels.

Visual acuity: The clarity or clearness of the vision, a measure of how well a person sees. The ability to distinguish details and shapes of objects; also called central vision.
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Visual field: The entire area that can be seen when the eye is directed forward, including that which is seen with peripheral vision.
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Vitamin A: Vitamin A is retinol. Carotene compounds (found, for example, in egg yolk, butter and cream) are gradually converted by the body to vitamin A (retinol). A form of vitamin A called retinal is responsible for transmitting light sensation in the retina of the eye.
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Vitamin C: An essential nutrient found mainly in fruits and vegetables. The body requires vitamin C to form and maintain bones, blood vessels, and skin.
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Vitamin E: Alpha-tocopherol, an antioxidant vitamin which binds oxygen free radicals that can cause tissue damage. Deficiency of vitamin E can lead to anemia. Vitamin E may play a possible role in preventing heart disease and cancer of the lung and prostate.
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Vitamins: The word "vitamin" was coined in 1911 by the Warsaw-born biochemist Casimir Funk (1884-1967). At the Lister Institute in London, Funk isolated a substance that prevented nerve inflammation (neuritis) in chickens raised on a diet deficient in that substance. He named the substance "vitamine" because he believed it was necessary to life and it was a chemical amine. The "e" at the end was later removed when it was recognized that vitamins need not be amines.
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Vitrectomy: Removal of the gel (called the vitreous) from within the eyeball. This may be done because it has blood and scar tissue in it that blocks sight. An eye surgeon then replaces the clouded gel with a clear fluid.

Wasting: 1. Gradual loss (for example, of weight), deterioration, emaciation. As in a wasting disease. 2. Excessive depletion. As in salt wasting, the excessive loss of salt.

Zinc: A mineral essential to the body, zinc is a constituent of many enzymes that permit chemical reactions to proceed at normal rates. It is involved in the manufacture of protein (protein synthesis) and in cell division. Zinc is also a constituent of insulin, and is concerned with the sense of smell.
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