Glossary

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Video Magnifier(also: CCTV Magnifier, Electronic Magnifier, Desktop Video Magnifier)

An assistive device that uses a camera to capture and display magnified images of printed material, objects, or other visual content on a screen. Video magnifiers range from portable handheld units to desktop models with large monitors. For musicians with low vision, handheld…

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…

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 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 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 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 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 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 Search Strategy(also: Scanning Strategy, Visual Scanning)

Systematic approaches to visually exploring an environment or scene to locate specific objects, patterns, or information. In low-vision rehabilitation, therapists train clients in efficient search strategies such as systematic scanning patterns (horizontal, vertical, spiral),…

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…

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