ScotomaPlaque-forming unit: In virology, a plaque-forming unit (PFU) is a measure of the number of particles capable of forming plaques per unit volume, such as virus particles. It is a functional measurement rather than a measurement of the absolute quantity of particles: viral particles that are defective or which fail to infect their target cell will not produce a plaque and thus will not be counted.Meridian (perimetry, visual field): Meridian (plural: "meridians") is used in perimetry and in specifying visual fields. According to IPS Perimetry Standards 1978 (2002): "Perimetry is the measurement of [an observer's] visual functions ...Scanning laser ophthalmoscopyPurtscher's retinopathy: Purtscher's retinopathy is a disease where part of the eye (retina) is damaged. Usually associated with severe head injuries, it may also occur with other types of trauma, such as long bone fractures, or with several non-traumatic systemic diseases.Spalding MethodLogMAR chart: A LogMAR chart comprises rows of letters and is used by ophthalmologists and vision scientists to estimate visual acuity. This chart was developed at the National Vision Research Institute of Australia in 1976, and is designed to enable a more accurate estimate of acuity as compared to other charts (e.Homonymous hemianopsiaAge-Related Eye Disease Study: The Age-Related Eye Disease Study (AREDS) was a clinical trial sponsored by the National Eye Institute, one of the National Institutes of Health in the United States.A Randomized, Placebo-Controlled, Clinical Trial of High-Dose Supplementation With Vitamins C and E, Beta Carotene, and Zinc for Age-Related Macular Degeneration and Vision Loss.Low vision assessment: Low vision is both a subspeciality and a condition. Optometrists and Ophthalmologists after their training may undergo further training in Low vision assessment and management.Mark III (radio telescope): The Mark III was a portable and fully steerable radio telescope located at Wardle, near Nantwich, Cheshire in the north-west of England (at ). Constructed in 1966, it was remotely controlled from Jodrell Bank Observatory, and was mainly used as part of the MERLIN radio telescope network.Macula of retina: The macula or macula lutea (from Latin macula, "spot" + lutea, "yellow") is an oval-shaped pigmented area near the center of the retina of the human eye. It has a diameter of around .Tactical light: A tactical light is a flashlight used in conjunction with a firearm to aid low light target identification, allowing the marksman to simultaneously aim and illuminate the target. Tactical lights can be handheld or mounted to the weapon with the light beam parallel to the bore.Optokinetic reflexLandolt CBraille technology: Braille technology is assistive technology which allows blind or visually impaired people to do common tasks such as writing, browsing the Internet, typing in Braille and printing in text, engaging in chat, downloading files, music, using electronic mail, burning music, and reading documents. It also allows blind or visually impaired students to complete all assignments in school as the rest of sighted classmates and allows them take courses online.