Glossary

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Video accessibility(also: Accessible video, Video a11y)

The practice of making video content perceivable, operable, and understandable for people with disabilities. This encompasses captions for deaf and hard-of-hearing viewers, audio descriptions for blind users, visual enhancements for low-vision users, and controls that work with…

Virtual World Accessibility(also: Metaverse Accessibility, VR Accessibility for Blind Users)

Virtual world accessibility refers to the design and implementation of techniques that enable people with disabilities, particularly blind and visually impaired users, to participate in 3D virtual environments such as online virtual worlds, VR platforms, and metaverse…

Visual Acuity(also: VA, Sharpness of Vision)

A measure of the eye's ability to distinguish fine details and shapes at a given distance. Visual acuity is commonly expressed as a Snellen fraction (e.g., 20/20, 20/200) or in logMAR units used in clinical research. It is the primary metric for classifying levels of vision…

Visual Hallucination(also: AI hallucination, MLLM hallucination)

In the context of multimodal AI systems, visual hallucination refers to the generation of descriptions or responses that contain information not grounded in the actual visual input—fabricating non-existent objects, misattributing properties such as colour or size, or…

Visual Impairment(also: Vision Impairment, Low Vision, Sight Loss)

A reduction in the ability to see that cannot be fully corrected with standard glasses, contact lenses, or medical treatment. Visual impairments range from low vision (partial sight) to total blindness and include conditions like macular degeneration, glaucoma, diabetic…

Visual Interpretation Service(also: VIS, Visual Assistance Service, Remote Sighted Assistance)

A service that provides visual information to blind and low vision users through human assistants, AI-powered tools, or a combination of both. Traditional visual interpretation services like Aira connect users via video call to trained human agents who describe visual…

Visual Privacy(also: Visual Information Privacy)

The safeguarding and management of sensitive visual information that could be shared or disclosed in everyday life, particularly through the use of assistive technologies and generative AI tools. For blind and low vision users, visual privacy encompasses multiple dimensions:…

Visual Profile(also: Visual Function Profile)

A visual profile is a comprehensive characterization of an individual's visual capabilities across multiple dimensions, typically including visual acuity, contrast sensitivity, visual field, and color perception. In accessibility, understanding a user's visual profile is…

Visual Question Answering(also: VQA)

A task in which a system receives an image and a natural language question about that image, then generates a natural language answer. VQA emerged as a key accessibility paradigm through services like VizWiz, where blind users could submit photos with questions and receive…

Visual acuity(also: VA, LogMAR acuity, Snellen acuity)

A measure of the sharpness or clarity of vision, typically expressed as a Snellen fraction (e.g., 20/20, 20/200) or LogMAR value. A person with 20/200 vision must be 20 feet away to see what someone with normal vision sees at 200 feet. Visual acuity of 20/200 or worse in the…

Visual field loss(also: Peripheral vision loss, Scotoma, Tunnel vision)

A reduction in the area of vision that a person can see, either in the periphery (peripheral vision loss or tunnel vision) or in the center (central vision loss or central scotoma). Visual field loss is caused by conditions such as glaucoma, retinitis pigmentosa, stroke, and…

Visual guidance(also: Visual cueing, Visual highlighting)

Assistive techniques that direct a user's visual attention to relevant content through highlights, outlines, magnification, or other visual cues. For people with low vision, visual guidance systems can compensate for reduced visual acuity or restricted visual fields by making…

Visual processing(also: Visual perception, Visual cognition)

The brain's ability to interpret, organise, and make sense of visual information received from the eyes, involving multiple neural pathways including the ventral stream (object recognition, "what" pathway) and the dorsal stream (spatial awareness and motion, "where" pathway).…

Visual question answering(also: VQA, Visual QA)

A computer vision and natural language processing task in which a system answers natural language questions about the content of an image or video. In accessibility contexts, VQA enables blind and visually impaired users to query visual content interactively — asking specific…

Visual search

The perceptual task of scanning a visual scene to locate a specific target among distractors. Visual search is significantly affected by low vision, visual field loss, and other visual impairments, as reduced acuity or restricted fields make it harder and slower to locate…

Visual substitution(also: Sensory substitution, Vision substitution)

Visual substitution is a design strategy in assistive technology that replaces visual information with output in another sensory modality, such as audio descriptions, haptic feedback, or tactile representations. It contrasts with visual enhancement, which amplifies or augments…

Visually Impaired(also: Vision Impairment, Visual Impairment, BVI)

An umbrella term for any degree of reduced visual function that cannot be fully corrected with standard glasses or contact lenses, ranging from mild low vision to total blindness. The term is frequently combined as BVI (blind and visually impaired) in accessibility research to…

Voice and Video-Capable Language Model(also: VVLM, Multimodal AI Assistant, Video-Capable LLM)

A large language model that can process real-time or near-real-time video and audio input alongside text, enabling conversational interaction about the visual world. VVLMs represent a shift from static image analysis (single photo question-answering) to dynamic, continuous…

Voicemarking(also: Voice Bookmark, Speech-Based Bookmark)

A speech-based technique for creating and retrieving semantic bookmarks in assistive web browsers. Users create voicemarks by speaking the name of a concept (e.g., "Major Headlines") and optionally a keyword, allowing them to later jump directly to that content on any website…

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