GLOSSARY

Achromatopsia

Achromatopsia is a type of cone dystrophy where there are normally problems only with vision from cone photoreceptors, the ones responsible for color and day vision and visual acuity.

Adult Stem Cell

A self-renewing, unspecialized cell that is capable of becoming any one of a number of more specialized cells. A stem cell is a primitive, unspecialized cell that has the capacity to self-regenerate, but develops a highly specialized function when grown in the appropriate environment and treated with specific proteins or survival factors. In other words, it's a cell that "hasn't decided what it wants to be when it grows up." Stem cells in the human retina have been found in the ciliary body, a specialized structure that sits on either side of the iris, near the retina. These ciliary stem cells usually lie dormant in the adult. Stem cells have now been isolated by many scientific groups and are being evaluated as a potential source for replacement of RPE and photoreceptor cells. There are many different types of stem cells, including adult and embryonic stem cells. Adult stem cells are from mature tissue that can renew itself but has a limited ability to transform into specialized cell types (i.e., fewer cell options). Embryonic stem cells, being from early stages of development, have the theoretical potential to produce any kind of cell in the body.

Age-Related Eye Disease Study

AREDS was a clinical study sponsored by the Federal government's National Eye Institute that determined a specific nutritional supplementation regimen for slowing progress of vision loss in individuals with AMD. The AREDS supplementation is: Antioxidants (500 mg Vitamin C, 400 IU Vitamin E, 15 mg Beta-carotene) and Minerals (80 mg Zinc Oxide, 2mg Copper). Another study-AREDS II, started in October 2006-is designed to test modified minor adjustments to the original supplement combinations (e.g., removing beta-carotene from the formulation, lowering zinc), along with different dosages of lutein, zeaxanthin and/or omega-3 fatty acids. If you use nutritional supplementation, please consult with your personal physician and ophthalmologist as your personal health situation may require monitoring or a non-typical approach and nutritional supplements may interfere with prescribed medicines.

Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a retinal degenerative disease that causes a progressive loss of central vision. AMD is the most common cause of vision loss in individuals over 55. An estimated 10 million people in the U.S. either have AMD or are at substantial risk of developing it.

Angiogenesis

The growth of new blood vessels. When growing in places they shouldn't, they can cause disease, such as wet age-related macular degeneration (AMD). Angiogenesis refers to the growth of new blood vessels. When uncontrolled, angiogenesis can cause destruction of the retina due to leakage of blood.

Antioxidant

A nutritional supplement (like vitamins C or E), drug, or naturally occurring product that protects cells from damage induced by light, stress or metabolic processes (called oxidation). Antioxidants are also prevalent in foods, such as vegetables and fruits.

Apoptosis or Programmed Cell Death

A controlled process for cell death, triggered by a signal or biochemical reaction, in response to an accumulation of cellular damage..

AREDS (Age-Related Eye Disease Study)

AREDS was a clinical study sponsored by the Federal government's National Eye Institute that determined a specific nutritional supplementation regimen for slowing progress of vision loss in individuals with AMD. The AREDS supplementation is: Antioxidants (500 mg Vitamin C, 400 IU Vitamin E, 15 mg Beta-carotene) and Minerals (80 mg Zinc Oxide, 2mg Copper).

Autosomal Dominant Disease

Disease caused when an individual inherits a disease-causing mutation in one copy of a gene pair.

Autosomal Recessive Disease

Disease caused when an individual inherits a mutation(s) that may not cause disease unless both copies of a gene pair are mutated.

Autosome

Any chromosome within the 22 pairs of non-sex (not X or Y) chromosomes inherited by every individual from their biological parents. An autosome is a chromosome (or DNA package) that does not play a primary role in determining a person's sex (i.e., not an X or Y chromosome). Autosomal recessive and autosomal dominant diseases are caused by mutations in genes that reside on one of the 22 paired autosomes.

Bardet-Biedl Syndrome (BBS)

Bardet-Biedl syndrome is a complex disorder that affects many parts of the body including the retina. Individuals with BBS have a retinal degeneration similar to retinitis pigmentosa (RP).

Best Disease

Best disease is an inherited form of juvenile macular degeneration characterized by a loss of central vision..

Beta-carotene

A nutritional pigment (and antioxidant) that can be used in the visual cycle of the eye. It is responsible for the orange color of carrots and other fruits and vegetables.

Bruch's membrane

The blood-retina barrier that separates the retina from the rest of the body, that is often broken in individuals with wet AMD. The Bruch's membrane is the blood-retina barrier that separates the RPE cells of the retina from the choroid. This membrane is structurally similar to the blood-brain barrier, because the retina is an extension of the brain. A rupture of this barrier can cause diseases, like AMD, where the choroid blood vessels grow abnormally into the retina and cause damage, ultimately affecting vision.

Carotenoids

Tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building blocks by all these organisms.

Cell Based Therapy

Using cell transplants or stem cells to treat a retinal degenerative disease. Cell-Based Therapy (CBT) is one of the Foundation's seven research priority areas. Scientists and clinicians are testing treatments for retinal degenerative diseases with stem cell and retinal transplants. This therapy has the potential to treat all retinal degenerative diseases, even in those people who have completely lost all photoreceptor and/or RPE cells.

Cell

The smallest building-block of a living being that is capable of functioning on its own. A cell is the smallest biological unit of specialized function capable of self-replication. A cell consists of an outer membrane (like a porous plastic bag), which encases the fluid of the cell, and the nucleus (a specialized compartment that contains the DNA and directs the production of proteins). Conversion of many cells (of either the same or different functions) at the same spot in the body can form an organ with specialized purposes, like the retina, liver or brain.

Cellular and Molecular Mechanisms of Disease (CMM)

Cellular and Molecular Mechanisms of Disease (CMM) is one of the Foundation's seven research priority areas. Scientists and clinicians are determining how mutations in each identified gene cause retinal degenerative disease and specifically what goes wrong in the cells of the eye as a result of this mutation. The resulting knowledge is being used to create effective, directed treatments.

Central Nervous System

The "central command system" of the body, it includes the brain, spine and retina. The central nervous system (CNS) is the "central command system" of the body, and includes the brain, spine and retina. Every nerve outside of the blood-brain and blood-retina barriers is considered part of the peripheral nervous system. Since the retina is part of the CNS, it is possible that treatments for other neurodegenerative diseases of the CNS (like Lou Gehrig's disease or Alzheimer's disease) could work for retinal degenerative diseases.

Choroideremia

Choroideremia is a rare inherited disorder that causes progressive loss of vision due to degeneration of the choroid and retina.

Chromosome

A "package" of DNA that holds the genetic code to life. In humans, each non-sex cell has 23 pairs of chromosomes.

Cilia (singular, Cilium)

Cilia are very small, hair-like structures that are found in or on many specialized cell types (for example, photoreceptors and ear, kidney, and lung cells). A mutation in a gene whose protein helps maintain the structure of these "hairs" can cause diseases with symptoms in one or more affected body systems, creating a syndrome. For example, some Usher syndromes involve vision and hearing problems, caused by altered cilia proteins found in both photoreceptors and ear cochlear cells.

Ciliary Body

A ring of tissue that contains muscles and "fibers" that adjust lens thickness to focus light on the retina, so that we can see. In addition, it produces fluid to provide nutrients and take away waste from the lens and cornea, thus helping to control eye pressure.

Cone Cell

A type of photoreceptor, it detects light and is responsible for providing fine detail, daylight and color vision.

Cone Dystrophy

see Achromatopsia

Cone-Rod Dystrophy

Cone-rod dystrophy results from a primary loss of cone photoreceptors, followed by loss of rods.

Congenital Stationary Night Blindness (CSNB)

An inherited eye disorder that is not progressive ("stationary") and principally affects the rod photoreceptors in the retina, impairing night vision. There may also be moderate to high myopia (short sightedness). The disorder is usually diagnosed by electroretinogram.

Copper

A nutritional mineral that is required for proper functioning and maintenance of the body.

Cornea

The clear dome or "window" that covers the front of the eye, it provides a large part of the focusing ability of the eye. The cornea is the clear dome that covers the front of the eye. It starts to focus light onto the lens. If the eye is like a camera, consider the cornea to be like a UV (ultraviolet) filter screwed onto the end of the camera lens. This is the part of the eye that undergoes vision-correcting LASIK surgery.

Cortical implant

An implant into the part of the brain that interprets vision signals that come from the retina. Connecting this implant with a vision aide, like camera-glasses, may be a way to return vision to those who are blind.

CSNB

see Congenital Stationary Night Blindness

DHA (docosahexaenoic acid)

A healthy, highly unsaturated fatty acid (a type of omega-3 fatty acid) that is found in foods (e.g., tuna, salmon) and dietary supplements, implicated in photoreceptor function.

DNA (deoxyribonucleic acid)

The chemical "blueprint" for life. Genes are made of DNA and gene mutations can cause diseases.

Dominant

see Autosomal Dominant Disease .

Drusen

Yellow-white retinal deposits thought to include proteins, pigments and fats. Dry AMD or juvenile macular degeneration may occur when drusen become too large or numerous and collect around the macula. .

Embryonic Stem Cell

see Stem Cell .

FDA

Acronym for the Food and Drug Administration, a branch of the United States (US) Department of Health and Human Services.

FFB

Acronym for Foundation Fighting Blindness.

Free Radical

A highly reactive chemical or nutritional breakdown product that can cause damage to a cell or tissue.

GA

see Gyrate Atrophy or Geographic Atrophy and Age-related Macular Degeneration

GE

see Genetics

Gene

A unit of inheritance, encoded by DNA. If there's a mutation in a gene, this may cause a disease.

Gene Mapping

Identifying a region of a chromosome that is responsible for causing a disease (or causing some known function), but not yet identifying the exact gene.

Gene Therapy (GT)

A therapeutic process that replaces or turns off the "bad" or mutated disease-causing gene and restores some level of normal protein function.

Genetic Testing (also called Genotyping)

Generally, is defined as determining the genetic make-up of an individual; specifically, is looking for the gene(s) that cause an individual's retinal degenerative disease.

Genetics (GE)

Generally, it is defined as the study of inheritance; specifically, it is the determination of genes linked with causing retinal degenerative diseases. Genetics (GE) is one of the Foundation's seven research priority areas. Scientists and clinicians are looking for new genes linked to retinal degenerative diseases. It is thought that over half of retinal degenerative disease-causing genes have already been identified.

Geographic Atrophy (GA)

Geographic atrophy may be considered the end stage of dry age-related macular degeneration (AMD), causing severe vision loss. Over time, sometimes over many years, the atrophy of the RPE cells (due to drusen deposits in the retina) gets more prevalent with all of the macula being affected. Geographic atrophy looks like a circle or spot of degeneration, right in the center. Also see Age-related Macular Degeneration.

Gyrate Atrophy (GA)

Gyrate atrophy is an autosomal recessively inherited disorder, which is due to a lack of the protein enzyme ornithine keto-acid aminotransferase (OAT), resulting in an increased blood serum level of ornithine (hyperornithinemia). The symptoms are progressive "night blindness" and peripheral vision loss.

Inner Segment

The part of a photoreceptor cell that is closest to the front of the eye and is thought to channel light to the outer segment, where the visual cycle takes place.

Iris

The colored "ring" that regulates the amount of light that's admitted into the eye. An iris is the colored "ring" surrounding the pupil that regulates the amount of light that is admitted into the eye. If the eye is like a camera, consider the iris to be like an aperture.

Juvenile Macular Degeneration

see Best Disease; Stargardt Disease

Lancelot

A Briard dog born blind with a mutation in the RPE65 gene that caused a dog-form of the human retinal degenerative disease called Leber congenital amaurosis (LCA). Lancelot has been treated with gene therapy and can now see. As reported in the scientific journal, Nature Genetics, in 2001, researchers injected into one of Lancelot's eyes a "good" copy of the RPE65 gene that corrected his vision in that one eye. Since Lancelot's treatment, over 50 dogs have been treated in a similar manner and can now see. Three human clinical trials based upon this research began in 2007.

Leber Congenital Amaurosis (LCA)

Leber congenital amaurosis (LCA) is an inherited retinal degenerative disease characterized by severe loss of vision at birth. A variety of other eye-related abnormalities including roving eye movements, deep-set eyes, and sensitivity to bright light also occur with this disease. Some patients with LCA also experience central nervous system abnormalities.

Lens

The transparent part of the eye that focuses light onto the retina, so that we can see. The lens is an oval-shaped, clear (transparent) part of the eye behind the cornea and iris that focuses incoming light onto the retina. If the eye is like a camera, consider the eye lens to be like a camera lens.

Locus (plural, Loci)

A locus is the chromosomal "neighborhood" where a gene (a "house") resides; specifically, a potential disease-causing gene. A locus is a location in one part of a chromosome where a particular gene(s) might reside, like a "house" (gene) might reside in a "neighborhood" (locus). Scientists who are looking for genes associated with retinal degenerative diseases call it a locus until they definitively prove that one (or more) gene(s) in this region cause(s) that disease.

Lucentis®

A blood vessel growth-blocking drug approved by the FDA in June 2006 for treatment of wet AMD.

Lutein and Zeaxanthin

Nutrient pigments chemically related to beta-carotene that are abundant in green leafy vegetables and yellow and orange-colored fruits and vegetables. These are the only two known food pigments that collect in the macula, where they are thought to protect it from light damage (blue light).

Macugen®

An anti-VEGF drug approved by the FDA in 2004 for treatment of wet AMD. Macula The center of the retina that has a concentration of cone photoreceptor cells and is responsible for fine detail, day and color vision. The macula is the central portion of the retina. The macula contains a dense concentration of cone photoreceptor cells that help us to see fine visual detail (see Visual Acuity), daylight and color vision. Only primates (including humans and monkeys) have a macula in their retina.

Messenger RNA (mRNA)

The processed gene "messenger" (derived from DNA) that is the template for making proteins. Also, see RNA. Messenger RNA (mRNA) is the gene messenger that results from the transfer of genetic information from DNA into RNA. Often the orginal mRNA requires processing (i.e., cutting and "re-glueing") into a shorter mRNA template for production of the final, proper protein.

Metabolic process

A series of pathways the body uses, both to break down nutrients into simple energy packets and to create building blocks that then build-up cell components and help the body to function.

Mutation

A change or "spelling mistake" in the DNA of a gene that can cause a disease (but sometimes does not cause disease).

NEI

Acronym for the National Eye Institute, a part of the research-funding government organization, the United States (US) National Institutes of Health. Neuroprotective Therapy (NP) Delivering a protein or drug to the eye that prevents the photoreceptors and/or RPE cells from dying, thus saving vision.

Nucleus

The specialized compartment within a cell that houses the DNA. The nucleus is the specialized compartment within a cell that houses the DNA, packaged as chromosomes. The nucleus is also the location where RNA (messenger RNA) is made from genes and transported out of the nucleus to serve as a template for protein production.

Nutritional and Environmental Therapy (NE)

A clinically-tested nutritional supplement or lifestyle change that has been proven to slow or stop the loss of vision in a retinal degenerative disease.

Nystagmus

Nystagmus is a constant, rapid and involuntary oscillation of the eyes - one of the symptoms that can be experienced by individuals who have a retinal degenerative disease, like Leber congenital amaurosis.

Omega-3 fatty acid

A type of fat that is important for cell function. Also, see DHA.

Optic Nerve

The bundle of nerve cells, or "cable," that transmits signals from the retina to the visual processing center of the brain. The optic nerve is the "cable" that receives the light detection signals from other retinal cells (photoreceptors initially detect the photons of light) and transports them to the part of the brain called the visual cortex where they are processed. A person doesn't actually "see" until their visual cortex processes the signals. If the eye is a digital camera, consider this to be like the cable used to download the images from the camera onto a computer.

Outer Segment

The part of the photoreceptor cell that is directly adjacent to RPE cells, near the back of the retina, and is responsible for the conversion of light into electrical signals, via the visual cycle.

Oxidative Stress/Oxidation

Oxidation is the interaction between oxygen molecules and all the different substances they may contact. Oxidative Stress can occur when there's an imbalance and a biological system can't readily detoxify or easily repair the resulting damage, thereby promoting development of a retinal degenerative disease).

Peripheral Nervous System

Nerves that are not part of the brain, spinal cord or retina, normally found in the extremities (e.g., arms, legs).

Phagocytosis

The process by which cells engulf materials (e.g., bacteria, dead cells) that are eventually killed, destroyed or digested. The outer segment tips of photoreceptor cells are phagocytosed every day by RPE cells.

Phenotype

Physical symptoms of a retinal degenerative disease that can be clinically defined. Each phenotype is normally associated with a particular genotype (see Genetic Testing). A phenotype consists of the observable characteristics or clinical symptoms present in an individual with a particular retinal degenerative disease. Scientists are attempting to correlate the phenotype with the genotype for every retinal degenerative disease.

Photodynamic Therapy

A therapy for the wet form of AMD that involves using a drug and a "cold" laser to destroy new, unwanted blood vessels.

Phototransduction

The process of detecting light and converting it to an electrical signal that is then relayed to the brain via the optic nerve. Phototransduction is also called the visual cycle. It is the cascade of biochemical reactions involved in detecting light and converting it to an electrical signal that is relayed to the brain via the optic nerve. Both photoreceptors and RPE cells are essential for this process. Problems with proteins involved in phototransduction are responsible for causing certain retinal degenerative diseases.

Proof of Principle

The first measurable evidence that an experimental theory or therapy works. A proof of principle is a scientific confirmation that a previously unproven idea or experimental therapy actually works (for instance, a drug produces a therapeutic effect in an animal model(s)). Proof of principle provides the first measurable evidence that an experimental therapy might also work in humans.

Recessive

see Autosomal Recessive Disease

Retina

Thin layer of light-detecting cells at the back of the eye, similar to the film or digital sensor found in a camera.

Retinal Chip (also called Artificial Retina)

A light-detecting computer chip, designed to mimic basic photoreceptor cell light-detection function, that is implanted into the retina.

Retinal Pigment Epithelium (RPE)

A very thin cell layer found directly beneath the photoreceptor cells. RPE cells bring nutrients and oxygen to the photoreceptor cells, and supplies, recycles, and detoxifies products involved with the phototransduction process.

Retinal Prosthetic

An implantable device that electrically stimulates the retina with information that it receives from a secondary light detection device (i.e., camera glasses).

Retinal Transplantation

Injecting a layer of cells (already composed of photoreceptor and/or RPE cells) into the retina to replace dying cells.

Retinal Vessels

The vessels found on top of the retina at the back of the eye that look like "tree branches" when viewed by an ophthalmologist during an eye exam. Retinal vessels are the vessels found on top of the retina at the back of the eye that look like "tree branches" when viewed by an ophthalmologist during an eye exam. These vessels become damaged and leaky during eye diseases like diabetic retinopathy, retinopathy of prematurity and other diseases.

Retinitis Pigmentosa (RP)

Retinitis pigmentosa (RP) refers to a group of inherited diseases causing retinal degeneration. The most common feature of all forms of RP is a gradual breakdown of rods and cones. Most forms of RP first cause the breakdown of rod cells. These forms of RP, sometimes called rod-cone dystrophy, usually begin with night blindness. RP is typically diagnosed in adolescents and young adults. It is a progressive disorder. The rate of progression and degree of visual loss varies from person to person. RP can be inherited in a dominant, recessive or X-linked fashion.

Retinoschisis (also known as X-Linked Retinoschisis; XLRS)

Retinoschisis is vision loss due to the splitting of retinal layers and retinal deterioration due to a mutation in the retinoschisin (RS1) gene. The RS1 protein is thought to act like a "glue" to hold together the retina. RS1 is an X-linked gene, where it is normally males who show symptoms of this disease. In addition to visible degeneration of the retina, the electroretinogram (ERG) is a negative (b-wave more reduced than a-wave).

Rhodopsin

A light-detecting component (a visual pigment) of rod photoreceptor cells composed of a protein called opsin that is chemically linked to a processed fragment of vitamin A.

Ribozyme Therapy

A form of gene therapy that reduces the amount of "bad" gene product ("bad" RNA) to allow "good" protein to be made from good, non-mutated RNA.

RNA

A family of gene products whose most common member, messenger RNA (mRNA), isused as a template for making protein. "Messenger" RNA (mRNA) is derived directly from a gene and becomes the template for making a protein. Scientists and clinicians are currently testing approaches that target mRNA in many treatments for retinal degenerative diseases.

RNAi Therapy

A treatment method that destroys "bad" RNA to get rid of "bad" disease-causing protein.

Rod Cell

A photoreceptor cell responsible for black and white, night and peripheral (side) vision. A rod cell is a rod-shaped photoreceptor cell that is located throughout the retina but is more common outside of the central macular region of the retina (i.e., is found in the periphery of the retina). The rod cell is particularly important for black and white, night and peripheral (side) vision. In many forms of RP, rod cell loss lead p-glossarys to what is sometimes referred to as "tunnel vision."

Rod-Cone Dystrophy/Degeneration

Rod-cone dystrophy results from a primary loss of rod photoreceptors, followed by loss of cones.

Sclera

The tough, outer, protective shell of the eye. The sclera, also called the "white of the eye" is the tough outer protective shell of the eye. If the eye is like a camera, consider the sclera to be like the camera body.

Sex Chromosomes

The chromosomes inherited from both parents that contain the genetic material that determines the sex of an individual. X-linked diseases are caused by mutations of genes on the X chromosome.

Stargardt Disease

Stargardt disease is the most common form of inherited juvenile macular degeneration. The progressive vision loss associated with Stargardt disease is caused by the death of photoreceptor cells in the central portion of the retina called the macula.

Stem Cell

A self-renewing, unspecialized cell that is capabile of becoming any one of a number of more specialized cells.

Strabismus

A misalignment of the eyes (pointing in and/or out). This situation may be due to eye muscle problems. A misalignment of the eyes in which each eye, simultaneously can point in a different direction. Crossed eyes (esotropia) are one type of strabismus; "wall-eyes" (exotropia) are another. The exact cause is unknown, but it appears to be a problem with the eye muscles. Strabismus can affect depth perception.

Survival Factors/Proteins

Also see Neuroprotective Therapy. Proteins, or drugs, that promote the health and survival of nerve cells, including photoreceptors.

Trans Fats

Unhealthy types of fat that may increase the risk of developing AMD.

Ultraviolet (UV) light

A radiant component of sunlight, invisible to the eye, that is characterized by short wavelengths and high energy. It will damage the retina (as well as the skin) with lengthy, unprotected exposure. If you use nutritional supplementation, please consult with your personal physician and ophthalmologist as your personal health situation may require monitoring or a non-typical approach and nutritional supplements may interfere with prescribed medicines.

Unsaturated Fatty Acid:

There are many different types of this dietary fat - some have been linked to positive health effects (see DHA; docosahexaenoic acid) and others have been linked to a risk of developing cardiovascular disease and AMD (see Trans Fats).

Usher Syndrome

Usher syndrome is an inherited condition characterized by hearing impairment and progressive vision loss. Balance may also be affected. Symptoms vary from person to person and progress at different rates. There are at least three different forms of Usher syndrome. People with Usher syndrome type 1 (USH1) are born completely deaf and experience problems with balance. The first signs of RP - night blindness and loss of peripheral vision - usually appear in early adolescence.

Vector

The "vehicle" or carrier for delivering genes or genetic information into the cell, particularly useful for gene therapy.

VEGF (Vascular Endothelial Growth Factor)

A class of proteins that causes new blood vessel growth (angiogenesis) and maintains the natural "leakiness" inherent in vessels. These are normal body functions, which, if they happen where they shouldn't (such as in the retina), can cause disease, such as AMD.

Verteporforin®

see Photodynamic Therapy

Visual Acuity

A measure of the ability to distinguish fine visual details. Visual acuity is the clarity of vision held by an individual and is measured as a fraction of normal vision: 20/20 vision indicates an eye that sees at 20 feet what a normal, "standard" eye should see at 20 feet; 20/400 vision indicates an eye that sees at 20 feet what a normal eye sees at 400 feet. Usually measured with a letter chart (Snellen), it can also be measured using pictures, black and white lines or visual evoked potentials.

Visual Cycle

see Phototransduction

Visual Field

The entire area that the eye can see from side to side without physically moving the eyes or head (includes peripheral vision). The portion of the environment that the eye sees, on fixed forward gaze, includes the entire field of vision (central and peripheral) and is measured by a perimetry test. The normal field of vision is about 140 degrees for each eye (monocular vision) and about 180 degrees for both eyes (binocular vision).

Visudyne®

see Photodynamic Therapy

Vitamin A (Vitamin A Palmitate)

see also Beta-carotene, Rhodopsin: Vitamin A is found in certain animal and milk products, fruits and vegetables (and as a commercial supplement) that is used as part of a nutritional treatment of RP.

Vitamin C (Ascorbic Acid)

An anti-oxidant found in certain fruits and vegetables (and as a commercial supplement) that is used as part of a nutritional treatment of AMD.

Vitamin E

An anti-oxidant found in certain oils, nuts, and other foods (and as a commercial supplement) that is also used as part of a nutritional treatment of AMD.

Vitreous

The clear, jelly-like substance found in the middle of the eye that helps to regulate eye pressure and shape. The vitreous is the clear, jelly-like substance found in the middle of the eye that helps to regulate eye pressure and shape. Light must pass through the vitreous to fall upon the retina, so it must be as transparent as possible to avoid vision distortion or disruption.

Wavelength

A measure of the character of light, where certain wavelength ranges define and distinguish different "types" of light. The photoreceptor cell detects and chemically converts light of certain wavelengths within the visible range (between 400-700 nanometers or nm) into electrical signals that travel, via the optic nerve, to the visual cortex in the brain.

X Chromosome

The inherited package (or chromosome) of DNA that contains genes that help to determine the sex of an individual. Two X chromosomes are inherited by females and one X chromosome and one Y chromosome are inherited by males. Mutation of a gene found on the X chromosome can cause X-linked diseases.

X-Linked Retinoschisis (XLRS)

see Retinoschisis

Y Chromosome

The chromosome (DNA package) passed-down from biological father to son that contains genes that determine male gender. The Y chromosome is the sex chromosome passed-down from biological father to son that contains genetic instructions that give men their gender (and other body characteristics). Males inherit one Y chromosome from their father and one X chromosome from their mother, and are therefore normally symptomatic if they have an X-linked disease. So far, there are no known retinal degenerative diseases linked to the Y chromosome.

Zinc

A mineral that is required for nutrition and proper function and maintenance of the body. Zinc oxide (80 mg) is one component of the daily nutritional supplementation for treatment to prevent progression of vision loss in AMD (findings from AREDS clinical trial). Zinc oxide is also being tested in a new nutritional supplement formulation for the AREDS II clinical trial. If you use nutritional supplementation, please consult with your personal physician and ophthalmologist as your personal health situation may require monitoring.