Glossary

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Virtual Wall(also: Haptic Wall, Haptic Boundary)

A simulated physical boundary in a haptic interface that the user can feel through a force-feedback device, modelled as a massless plate backed by a spring with stiffness and a damper with viscosity. Virtual walls are used to represent the edges and boundaries of graphical user…

Virtual World(also: Virtual Environment, Online Virtual World)

A computer-simulated environment where users interact with each other and digital objects through graphical representations, often in real time. Virtual worlds range from 2D browser-based platforms to fully immersive 3D social VR environments accessed through head-mounted…

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…

Virtual audit(also: Remote audit, Virtual streetscape audit, GSV audit)

A method of assessing the physical environment for accessibility features and barriers using street-level imagery such as Google Street View, rather than conducting in-person site visits. Virtual audits allow researchers and practitioners to evaluate conditions like sidewalk…

Virtual environment(also: Virtual world, VR environment, 3D virtual space)

A computer-generated simulation of a three-dimensional space that users can navigate and interact with, typically rendered visually through screens or head-mounted displays. Virtual environments range from simple 3D spaces to complex simulated worlds used in gaming, training,…

Virtual reality(also: VR, Immersive virtual environment)

A computer-generated simulation of a three-dimensional environment that users can interact with using specialized hardware such as head-mounted displays and motion controllers. Virtual reality presents significant accessibility challenges because most VR applications rely…

Viseme(also: Visual Phoneme)

The visual equivalent of a phoneme — the distinct mouth shape or lip position that corresponds to a speech sound as seen on a speaker's face. Unlike phonemes, which are auditory units, visemes are visual units that represent how the mouth looks during speech production. Multiple…

Visible Disability(also: Apparent Disability)

A disability that is readily apparent to outside observers through physical characteristics, mobility aids, or other visible indicators. Examples include amputations, paralysis, use of a wheelchair, or conditions that affect gait or posture. Visible disabilities shape social…

Vision Impairment(also: Visual Impairment, VI)

An umbrella term for any reduction in visual function — including low vision, blindness, and functional limitations that affect everyday tasks — regardless of cause. The World Health Organization distinguishes between distance and near vision impairment and further classifies…

Vision Language Model(also: VLM, Vision-Language Model, Multimodal Large Language Model)

A machine-learning model trained to take both images and natural-language text as input and to produce natural-language output. Modern VLMs — such as GPT-4o, Gemini, and Claude — can describe a photo, read text inside an image, answer questions about a scene, identify objects,…

Vision Multiplexing(also: Visual Multiplexing)

An optical engineering concept for low-vision aids that involves presenting multiple views or visual channels simultaneously to compensate for reduced visual function. In the context of assistive technology, vision multiplexing allows users to see both a wide field of view and a…

Vision Rehabilitation(also: Visual Rehabilitation)

See Low-Vision Rehabilitation. A comprehensive set of services and interventions designed to help people with vision loss maximize their remaining vision and develop adaptive strategies for independent living. Vision rehabilitation encompasses assessment, training, assistive…

Vision Therapy(also: Visual Training, Orthoptics, Eye Training)

A program of visual activities and exercises prescribed to improve visual skills and processing, often used to treat conditions like amblyopia, strabismus, and convergence insufficiency. Vision therapy can include in-office sessions and at-home exercises, and increasingly…

Vision User(also: VU, Sighted User)

A person who primarily uses vision to access digital content, interacting with web pages and applications through visual scanning, mouse/trackpad pointing, and visual recognition of interface elements. Vision users can rapidly skim content, identify relevant elements through…

Vision-Language Model(also: VLM, Multimodal AI Model, Large Multimodal Model)

An artificial intelligence model that can process and reason about both visual (image/video) and textual information simultaneously. Vision-language models like GPT-4o, Claude, and Gemini can describe images, answer questions about visual content, and generate text based on…

Vision-and-Language Navigation(also: VLN)

Vision-and-language navigation is a task setup in which an agent follows natural-language instructions to move through a visual environment, grounding words like 'turn left at the blue sofa' onto what it sees in real time. Research in VLN has moved from small indoor simulators…

Vision-based Page Segmentation(also: VIPS)

A web page segmentation algorithm that uses both the source code and the visual presentation of a web page to divide it into hierarchical visual blocks. VIPS produces a tree structure where the root node represents the entire page and leaf nodes represent the smallest meaningful…

Vista Space(also: Vista)

In Montello's classification of psychological spaces, a Vista is a far-field space that can be visually apprehended from a single vantage point without appreciable locomotion - a horizon view, a city skyline, a mountain panorama. Vista spaces matter to accessibility because they…

Visual Aberration(also: Optical Aberration, Refractive Error)

A deviation from ideal optical performance in the eye that causes images to appear blurred, distorted, or otherwise degraded on the retina. Visual aberrations include both lower-order aberrations (such as myopia, hyperopia, and astigmatism) and higher-order aberrations (such as…

Visual Access Technology(also: Visual Assistance Technology, Visual Access Tools)

Technologies that help blind and low vision people understand visual content in both digital and physical environments. Traditional visual access technologies include screen readers, magnification software, and human-powered description services (like Be My Eyes with volunteer…

Visual Acuity

A measure of the sharpness or clarity of vision, typically expressed as a fraction (e.g., 20/20) or percentage indicating the smallest detail a person can resolve at a standard distance. Visual acuity is one of the primary metrics used to classify the degree of visual…

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 Aesthetics(also: Aesthetic Quality, Visual Appeal)

The subjective qualities of visual content that contribute to its perceived beauty, mood, style, and emotional impact, including elements like color harmony, composition, lighting, contrast, and overall visual coherence. In accessibility contexts, conveying visual aesthetics to…

Visual Affordance(also: Visual Affordances)

A visually conveyed cue that signals how an object can be used or what it represents - for example, a handle suggesting 'grasp', a button suggesting 'press', or color and labeling suggesting product identity. Many visual affordances are inaccessible through touch alone: blind…

Visual Assistance Technology(also: VAT, Visual Aid App)

Mobile applications and devices that take videos or images as input and provide verbal, haptic, or other non-visual output to help blind and low vision people access visual information. VAT can be human-enabled (e.g., Be My Eyes, Aira) where remote sighted volunteers or agents…

Visual Assistant(also: Visual Assistant Skill)

Proposed by Gonzalez Penuela et al. (2026), the 'visual assistant' skill is a set of behaviours that an AI visual interpretation system must exhibit — beyond simply producing accurate captions — to meaningfully support blind and low-vision users in daily life. The nine proposed…

Visual Attention(also: Attentional Allocation, Gaze Behaviour)

The cognitive process of selectively focusing on specific parts of the visual field while filtering out other information. Visual attention determines which elements in a scene or interface a person notices, how long they focus on them, and in what order. Research has shown that…

Visual Attention Span(also: VAS, Visual Attention Window)

The number of distinct visual elements that can be processed simultaneously in a single glance. Visual attention span is a cognitive capacity linked to reading ability — when reading, the eyes fixate on a word and the visual attention span determines how many letters can be…

Visual Attention Split(also: Split Attention, Divided Visual Attention)

The cognitive challenge of needing to divide visual focus between two or more sources of information simultaneously. For deaf and hard of hearing people, visual attention split is a pervasive accessibility barrier: they must look at captions or a sign language interpreter while…

Visual Augmentation(also: Text Augmentation, Visual Enhancement)

The addition of visual elements such as icons, images, sign language videos, or highlights to text to aid comprehension and reading support. Visual augmentation is a common reading support strategy across disability communities — for deaf and hard of hearing readers, it may…

Visual Clutter(also: Visual Noise, Visual Complexity)

An excess of visual elements in an environment or interface that makes it difficult to locate, identify, or focus on relevant information. Visual clutter is a significant barrier for people with cerebral visual impairment, simultanagnosia, and other visual processing conditions,…

Visual Cognition(also: Visual Processing, Visual Perception)

The set of mental processes involved in perceiving, interpreting, and responding to visual information, including object recognition, spatial awareness, motion detection, and visual attention allocation. Deaf and hard-of-hearing individuals demonstrate heightened visual…

Visual Communication(also: VIC)

A method of conveying information, ideas, and meaning through visual elements such as images, icons, symbols, and pictographs rather than through spoken or written language. In accessibility contexts, visual communication systems are particularly important for people with…

Visual Context Switching(also: Visual Attention Switching, Gaze Switching)

The act of shifting visual focus between multiple sources of information, such as between a sign language interpreter and a presentation screen, or between captions and a speaker's face. For deaf and hard of hearing users, visual context switching is a significant accessibility…

Visual Crowding(also: Crowding)

A perceptual phenomenon in which the presence of nearby flanking characters or objects makes it harder to recognise a target character, especially in peripheral vision or when the target is small, low-contrast, or briefly viewed. Crowding jointly with limited visual span sets an…

Visual Data Exploration(also: VDE, data visualization exploration)

Visual data exploration is the interactive process of examining datasets through graphical representations such as charts, maps, and dashboards to discover patterns, trends, and anomalies. Accessibility considerations are critical because conventional visualizations rely…

Visual Description(also: Visual Content Description)

The practice of conveying visual information through non-visual means, primarily text or speech. Visual description encompasses various contexts including image descriptions, alternative text, audio description of video, and assessment descriptors for privacy tools. Research in…

Visual Descriptor(also: Visual Cue, Visual Doneness Indicator)

A description in instructions or content that relies on visual appearance to convey information, such as "cook until golden brown," "the mixture should be translucent," or "form into patties." Visual descriptors are a significant accessibility barrier for blind and visually…

Visual Dialogue(also: Visual Dialog, VisDial)

Visual dialogue is an AI task that involves holding a multi-turn natural language conversation about visual content such as an image or video frame. Unlike single-turn visual question answering (VQA), visual dialogue systems maintain context across multiple exchanges, using…

Visual Dispersion(also: Visual Attention Splitting, Gaze Switching)

The challenge faced by deaf and hard of hearing individuals when they must divide their visual attention between multiple simultaneous information sources, such as a speech-to-text display, presentation slides, a whiteboard, and the speaker. Unlike hearing individuals who can…

Visual Distraction(also: Visual Clutter, Visual Noise)

Visual elements in an interface or content that draw attention away from the primary content or task, including animated advertisements, moving backgrounds, decorative overlays, notification badges, recommended content panels, and complex visual layouts. Visual distractions are…

Visual Document Understanding(also: VDU, Document Understanding)

A field of AI research focused on the interpretation and analysis of visually-rich digital documents such as forms, tables, menus, reports, receipts, and academic papers. Visual document understanding goes beyond basic OCR text extraction by comprehending the spatial layout,…

Visual Epistemology(also: Sighted Epistemology)

Ways of knowing and understanding the world that are dependent on visual perception. Visual epistemology treats sight as the primary and most reliable sense for gathering information, often positioning visual evidence as more trustworthy or complete than information obtained…

Visual Evoked Potential(also: VEP, Visually Evoked Response, VERP)

A visual evoked potential (VEP) is an electrical signal generated by the brain's visual cortex in response to a visual stimulus, typically a flash of light or a pattern change. VEPs are measured using electrodes placed over the occipital lobe and extracted from background EEG…

Visual Expression(also: Visual Self-Expression)

The use of visual media — including photography, graphic design, social media posts, presentations, and art — to communicate identity, mood, intent, and personal style. Visual expression goes beyond functional content to encompass aesthetic choices like color palettes, filters,…

Visual Fatigue(also: Eye Strain, Asthenopia, Visual Strain)

Discomfort, tiredness, or reduced visual performance resulting from prolonged or intensive visual tasks. For people with low vision, visual fatigue can occur more quickly because they must exert greater effort to see, often using non-optimal parts of their retina (eccentric…

Visual Feedback(also: Visual Biofeedback)

A method of providing real-time visual information to a user about their actions, performance, or physiological state. In speech therapy and assistive technology, visual feedback systems display graphical representations of vocal output to help users understand and modify their…

Visual Fidelity(also: Graphical Fidelity, VF)

The degree to which a virtual environment replicates the visual detail, realism, and complexity of real-world settings. In accessibility contexts, visual fidelity affects cognitive load and task performance differently across user populations. Research shows that individuals…

Visual Field(also: Field of Vision)

The total area visible to a person when their eyes are fixated on a central point, including both central and peripheral vision. Visual field can be measured in degrees and is assessed through perimetry testing. Various eye conditions affect the visual field differently:…

Visual Field Loss(also: Visual Field Deficit, VFL, Field Loss)

A reduction in the area of vision that a person can see without moving their eyes or head. Visual field loss can affect any portion of the visual field — central, peripheral, or specific quadrants — and can result from conditions affecting the eyes (glaucoma, retinal detachment)…