Glossary

  • 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.

  • 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.

  • 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 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.

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