Glossary

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Guide Runner(also: Sighted Guide Runner, Running Guide)

A sighted person who accompanies a blind or visually impaired runner during training or competition, providing verbal navigation cues and physical guidance typically through a tether connecting the two runners. Guide runners must match the ability level of the BVI runner,…

Guide-by-Pointing(also: Point-and-Ask, Hand-Guided Visual Query)

A prompting technique for multimodal AI assistants where a user extends their hand into the camera's field of view and asks the AI to identify what they are pointing at, or to provide spatial directions for moving their hand toward a specific item. This technique enables blind…

Hand-Over-Hand Technique(also: Hand-Over-Hand Guidance, Hand-Over-Hand Training)

A training and communication method commonly used with individuals who are blind or have visual impairments, where a trainer places their hands over the learner's hands to physically guide them through the motions of a task. This technique allows the learner to feel the correct…

Hand-Under-Hand Technique(also: Hand-Under-Hand Guidance, Hand-Under-Hand Training)

A training and communication method used with individuals who are blind or have visual impairments, where the learner places their hands on top of the trainer's hands to feel the movements being demonstrated. Unlike hand-over-hand guidance where the trainer controls the…

Hyperopia(also: Farsightedness, Long-Sightedness, Hypermetropia)

A refractive error in which the eye focuses light behind the retina rather than on it, causing near objects to appear blurred while distant objects may remain relatively clear. Hyperopia occurs when the eyeball is too short or the cornea is insufficiently curved. It is…

Image sonification(also: Visual-to-audio mapping, Auditory image display)

The process of converting visual information from images — such as shapes, charts, diagrams, or spatial layouts — into audio representations that can be perceived without vision. Image sonification maps visual properties like position, size, colour, and shape to audio parameters…

Just-in-Time Prompting(also: Trigger-Based Prompting, On-Demand Visual Check)

A prompting technique for voice and video-capable AI models where the user pre-configures the AI with a role and task description, then uses a trigger phrase (such as "check now") to initiate an on-demand visual analysis of the current camera view. Developed as a workaround for…

Keratoconus

A progressive eye condition in which the normally round cornea thins and bulges into a cone-like shape, causing irregular astigmatism and significant visual distortion that cannot be fully corrected with standard glasses or contact lenses. Keratoconus typically begins in…

Kurzweil Reading Machine(also: KRM, Kurzweil Reader)

A pioneering reading device for blind people invented by Ray Kurzweil in 1976, combining optical character recognition (OCR) with text-to-speech synthesis to read printed text aloud. The original device was as large as a stove and produced mechanical-sounding speech, but it…

Late Blind(also: Adventitiously Blind, Acquired Blindness)

A person who lost their vision later in life, typically after age 5-7 when visual memories and concepts have been established. Late blind individuals often retain visual memories and may use these to construct mental representations of spaces and routes. Research suggests late…

Leber Hereditary Optic Neuropathy(also: LHON)

A maternally inherited genetic condition that causes sudden or rapid loss of central vision, typically affecting young adults between the ages of 15 and 35. LHON results from mutations in mitochondrial DNA that damage the optic nerve, leading to significant bilateral central…

Legal Blindness(also: Legally Blind)

A level of vision loss defined in many countries as visual acuity of 20/200 or less in the better eye with best correction, or a visual field of 20 degrees or less. Legal blindness does not necessarily mean total blindness — many legally blind people have some residual or…

Legal blindness(also: Legally blind)

A level of visual impairment defined in many jurisdictions as visual acuity of 20/200 or worse in the better eye with best correction, or a visual field of 20 degrees or less. Legal blindness is an administrative threshold used to determine eligibility for disability benefits…

Legally Blind(also: Legal Blindness)

A legal classification of visual impairment used to determine eligibility for government benefits, rehabilitation services, and disability accommodations. In the United States, legal blindness is defined as visual acuity of 20/200 or worse in the better eye with best correction,…

Line Chart Accessibility(also: Accessible Line Graphs, Chart Accessibility)

The practice of making line charts and graphs perceivable and understandable by people with visual impairments through alternative representations such as tactile graphics, sonification, speech descriptions, or multimodal interfaces. Accessible line charts must convey not just…

Link Preview(also: Link Destination Preview, Link Target Preview)

Information about the content or nature of a hypertext link's destination page, provided to users before they follow the link. Link previews help users make informed navigation decisions, reducing the costly trial-and-error of following links to discover their content and then…

Live Description(also: Real-Time Description, Live Audio Description)

The practice of providing descriptions of visual content in real time as events unfold, as opposed to scripted descriptions added during post-production of recorded media. Live description is used in contexts such as livestreaming, live theatre, sporting events, and…

Livestream Accessibility(also: Live Video Accessibility)

The practice of making live video broadcasts accessible to people with disabilities, particularly viewers with visual or hearing impairments. Livestreams present unique accessibility challenges because they feature multiple simultaneous visual elements (main video, webcams,…

LogMAR(also: Logarithm of the Minimum Angle of Resolution)

A standardised scale for measuring visual acuity based on the logarithm (base 10) of the minimum angle of resolution, used in the Bailey-Lovie eye chart and widely adopted in clinical vision research. A logMAR value of 0.0 corresponds to 20/20 (6/6) vision, with higher values…

Lookout(also: Google Lookout)

An Android accessibility application developed by Google that uses the smartphone camera and machine learning to identify objects, read text, scan documents, and describe surroundings for blind and partially sighted users. Lookout can identify currency, read food labels,…

Low Vision(also: Partial Sight, Partially Sighted)

A visual impairment that cannot be fully corrected by glasses, contact lenses, medication, or surgery, but where some usable vision remains. Low vision encompasses a wide range of conditions and severity levels, typically defined as visual acuity between 20/70 and 20/400 in the…

Low vision(also: Partial sight, Visual impairment)

A level of visual impairment that cannot be fully corrected with standard glasses, contact lenses, medication, or surgery, but retains some usable vision — distinguishing it from total blindness. Low vision encompasses a range of conditions affecting acuity, visual field,…

Macular Degeneration(also: AMD, Age-Related Macular Degeneration, ARMD)

A progressive eye condition affecting the macula — the central part of the retina responsible for sharp, detailed vision. It is the leading cause of severe vision loss in people over 50 in developed countries. Macular degeneration gradually destroys central vision while…

Macular Dystrophy(also: Macular Degeneration)

A group of inherited eye conditions that cause progressive damage to the macula, the central part of the retina responsible for sharp, detailed vision. Macular dystrophies, including Stargardt disease, result in reduced central vision while peripheral vision is typically…

Macular degeneration(also: AMD, Age-related macular degeneration, ARMD)

A progressive eye disease that damages the macula, the central part of the retina responsible for sharp, detailed vision. It is the leading cause of vision loss in people over 50, affecting central vision while typically leaving peripheral vision intact. This means people with…

Magnification inset(also: Magnified inset view, Zoom inset)

A user interface element that displays a magnified view of a specific region of content within a smaller window overlaid on the original view. Unlike full-screen magnification, an inset preserves the surrounding context while enlarging the area of interest. For low-vision users,…

Marburg Notation(also: Marburg Mathematical Notation, Marburg Braille)

A Braille-based mathematical notation system developed at the Deutsche Blindenstudienanstalt (German Institute for the Blind) in Marburg, Germany, and widely used in German-speaking countries for reading and writing mathematics. Marburg notation is a 6-dot Braille code optimized…

Math Accessibility(also: Mathematical Accessibility, STEM Accessibility)

The practice of making mathematical content — including formulae, equations, graphs, and geometric representations — accessible to people with disabilities, particularly those with visual impairments. Mathematical notation poses unique accessibility challenges because it is…

Meares-Irlen Syndrome(also: Irlen Syndrome, Visual Stress Syndrome, Scotopic Sensitivity Syndrome)

Meares-Irlen Syndrome is a perceptual processing disorder that affects how the brain processes visual information, causing symptoms of visual stress including pattern glare, perceptual distortions, eye strain, headaches, and discomfort when reading. Unlike dyslexia, it is not a…

Mental Map(also: Cognitive Map, Mental Model of Space)

An internal cognitive representation of a physical environment, including spatial relationships, landmarks, routes, and distances. For people with blindness or visual impairments, building a mental map of a route before traveling is a critical strategy for independent mobility,…

Meta Ray-Ban Smart Glasses(also: Ray-Ban Meta, Meta Smart Glasses)

Consumer smart glasses produced through a partnership between Meta and Ray-Ban that integrate cameras, speakers, and microphones into a conventional eyewear form factor. When paired with Meta's Live AI feature, these glasses enable hands-free, voice-activated interaction with…

Myopia(also: Nearsightedness, Short-Sightedness)

A common refractive error in which the eye focuses light in front of the retina rather than on it, causing distant objects to appear blurred while near objects remain clear. Myopia occurs when the eyeball is too long or the cornea is too curved, and affects an estimated 30% of…

NVDA(also: NonVisual Desktop Access)

A free, open-source screen reader for Microsoft Windows developed by NV Access. NVDA enables people who are blind or have low vision to use computers by reading on-screen text aloud through a speech synthesizer or outputting to a refreshable Braille display. As open-source…

Nemeth Code(also: Nemeth Braille Code for Mathematics and Science)

A specialized braille code developed by Abraham Nemeth for representing mathematics, science notation, and technical symbols. Nemeth Code provides a comprehensive system for expressing equations, fractions, subscripts, superscripts, and other mathematical constructs in braille.…

Neural Plasticity(also: Neuroplasticity, Brain Plasticity)

The brain's ability to reorganize itself by forming new neural connections throughout life. In the context of accessibility, neural plasticity explains how people who are blind or visually impaired develop enhanced auditory and tactile processing abilities—the brain regions that…

Nystagmus(also: Involuntary eye movement, Dancing eyes)

A condition characterized by involuntary, repetitive, rhythmic movements of the eyes, which may move side to side (horizontal), up and down (vertical), or in a circular pattern (rotary). Nystagmus can be congenital (present from birth) or acquired later in life due to…

Nystagmus(also: Involuntary Eye Movement, Dancing Eyes)

A condition involving involuntary, repetitive, and rhythmic movements of the eyes, which can be horizontal, vertical, or rotary. Nystagmus can be congenital (present from birth) or acquired later in life due to neurological conditions, medications, or other causes. It often…

Object Permanence

The cognitive understanding that objects continue to exist even when they cannot be directly perceived through sight, sound, or touch. This developmental milestone, typically achieved in infancy for sighted children, can develop differently in blind children who lack visual…

Obstacle Detection(also: Obstacle Avoidance)

Technology or techniques that identify physical barriers in a person's path and alert them in time to take corrective action. For people who are blind or visually impaired, obstacle detection systems use sensors (ultrasonic, infrared, LiDAR, or camera-based) embedded in devices…

Omnidirectional Camera(also: 360-Degree Camera, 360 Camera, Panoramic Camera)

A camera equipped with multiple wide-angle or fish-eye lenses that captures a complete 360-degree view of its surroundings in a single shot. The resulting equirectangular image can be projected into conventional perspective views for viewing or processing. In accessibility…

Orientation and Mobility(also: O&M)

A professional field and set of skills that enable blind and visually impaired people to travel safely and independently in their environments. Orientation refers to understanding one's position in space relative to landmarks and destinations, while mobility refers to the…

Orientation and mobility(also: O&M)

A professional discipline and set of skills that enable people with visual impairments to travel safely and independently through their environment. Orientation refers to understanding one's position relative to the surrounding environment using sensory cues, landmarks, and…

Perkins Brailler(also: Brailler, Braille Writer)

A mechanical device for writing braille, manufactured by the Perkins School for the Blind since 1951. The Perkins Brailler has six keys corresponding to the six dots of a braille cell, a space bar, a backspace key, and a line advance key, allowing users to emboss braille…

Photosensitivity(also: Light Sensitivity, Photophobia)

An abnormal sensitivity to light that can cause discomfort, pain, or visual disturbance. Photosensitivity affects many people with visual impairments and certain neurological conditions including migraine and epilepsy. In digital accessibility, photosensitivity considerations…

Pitch Mapping(also: Pitch-Y Mapping, Frequency Mapping)

A sonification technique that maps data values to auditory pitch, where higher values produce higher-pitched sounds and lower values produce lower-pitched sounds. In accessibility contexts, pitch mapping is commonly used to represent the vertical position (Y-axis) of data points…

Presbyopia(also: Age-Related Farsightedness)

An age-related vision condition where the eye gradually loses its ability to focus on nearby objects, typically becoming noticeable in the early to mid-40s. Presbyopia affects virtually everyone as they age and significantly impacts web accessibility, making small text difficult…

Presentation video(also: Lecture recording, Recorded lecture)

A video recording of an instructor delivering content alongside visual materials such as slides, whiteboards, or demonstrations. Presentation videos present unique accessibility challenges because they combine spoken content with visual actions like pointing, annotating, and…

Proactive description(also: Proactive notification, Unsolicited description)

The ability of an assistive system to automatically provide relevant visual or environmental information without requiring the user to explicitly request it. For blind and visually impaired users navigating real-world environments, proactive description is critical — a human…

QR code accessibility(also: QR code labels, Machine-readable labels)

The use of Quick Response (QR) codes as an alternative to Braille or printed text for encoding information in tactile graphics, product labels, or physical environments that can be read by smartphone cameras. QR codes can encode 45% more text than Braille in the same physical…

Relief Chart(also: 3D Chart, Haptic Chart, Relief Graph)

A tactile data visualization that uses height (the third dimension) to encode data values, making charts accessible to people with visual impairments through touch. Unlike flat tactile graphics that use only texture or raised lines, relief charts represent data magnitude through…