Glossary

Search results

Activities of Daily Living(also: ADLs, Daily Living Activities, ADL)

Routine tasks that people perform every day for self-care and independent functioning, including reading, cooking, grooming, dressing, and managing household items. For people with low vision, performing ADLs can be significantly impacted by reduced visual acuity, contrast…

Aniridia

A rare congenital eye condition involving the partial or complete absence of the iris, often accompanied by reduced visual acuity, light sensitivity (photophobia), nystagmus, and sometimes glaucoma or cataracts. Digital accommodations typically include high screen brightness…

Assistive Device(also: Assistive Aid, Low-Vision Aid)

Any device, tool, or technology that helps a person with a disability perform tasks that might otherwise be difficult or impossible. In low-vision contexts, assistive devices range from optical aids (magnifiers, telescopes, specialized glasses) to electronic devices (video…

Blue Cone Monochromatism(also: BCM, S-cone Monochromacy)

A rare inherited vision condition in which only the blue (short-wavelength) cones function, resulting in severely reduced color vision, reduced visual acuity, photophobia, and nystagmus. Affected individuals see the world in shades of blue and yellow and typically benefit from…

Blurred Vision Simulation(also: Vision Simulation, Low Vision Simulation)

A technique used in accessibility evaluation where evaluators simulate the visual experience of people with reduced visual acuity by artificially blurring their view of a website or application. Methods include using low vision simulation glasses (commercially available from…

Brightness Contrast(also: Luminance Contrast, Perceived Brightness Difference)

The difference in perceived brightness between two colors, typically between text and its background. Brightness contrast is a key factor in readability, especially for people with low vision, color vision deficiencies, or those viewing content in challenging lighting…

CCTV(also: Closed Circuit Television, Video Magnifier, Desktop Video Magnifier)

A camera-based magnification system used by people with low vision to enlarge text and images on a monitor. Traditional CCTVs consist of a camera mounted over a reading platform that captures material placed beneath it and displays it magnified on an attached screen. Modern…

CCTV Magnifier(also: Closed-Circuit Television Magnifier, Video Magnifier, Desktop Video Magnifier)

An assistive device that uses a camera to capture an image of text or objects and displays it magnified on a screen, typically a television or computer monitor. CCTV magnifiers are one of the most widely used low vision aids, offering high levels of magnification, adjustable…

Cataracts(also: Cataract)

A clouding of the eye's natural lens that causes blurry or hazy vision and increased sensitivity to glare. Cataracts are the leading cause of vision impairment worldwide and become increasingly common with age. People with cataracts may experience difficulty reading, reduced…

Central Vision Loss(also: Central Scotoma, Macular Vision Loss)

Loss of vision in the central part of the visual field, typically caused by conditions affecting the macula such as macular degeneration or Stargardt disease. Central vision is responsible for detailed tasks like reading, recognizing faces, and seeing fine detail. Musicians with…

Central Vision Loss(also: Central Field Loss, Central Scotoma)

Loss of vision in the central part of the visual field, typically caused by damage to the macula — the area of the retina responsible for sharp, detailed vision. People with central vision loss experience difficulty seeing fine details directly in front of them, often describing…

Color Blindness(also: Color Vision Deficiency, CVD, Colour Blindness)

A condition in which the ability to distinguish certain colors is reduced or absent, most commonly affecting the perception of red and green. Color blindness affects approximately 8% of males and 0.5% of females of Northern European descent. In music education, color-coded…

Color Filter(also: Color Filters, Display Color Filter)

An operating-system or browser-level feature that alters how colors are rendered on screen, including grayscale, inverted colors, and filters for protanopia, deuteranopia, and tritanopia color vision deficiencies. Used by low-vision users and users with color vision deficiency…

Contrast Sensitivity

The ability to distinguish between objects and their background based on differences in luminance or color. Contrast sensitivity is distinct from visual acuity and can be reduced even when acuity is relatively preserved. People with poor contrast sensitivity may struggle to read…

Cursor Locator(also: Pointer Locator, Cursor Finder, Find My Cursor)

A software utility that helps users find the position of their mouse pointer on screen when it has been lost from view. Cursor locators typically activate through a keyboard shortcut or by detecting pointer behavior such as rapid shaking, and then draw attention to the pointer's…

Deconvolution

A computational process that reverses the blurring effects of convolution in an optical or imaging system. In the context of visual accessibility, deconvolution is used to pre-process images displayed on a computer screen so that when viewed through an eye with known…

Depth Perception(also: Stereopsis)

The visual ability to perceive the relative distance of objects in three-dimensional space. Depth perception relies on binocular vision and other visual cues. Reduced depth perception can affect a persons ability to navigate physical environments safely, judge distances, and…

Diabetic Retinopathy(also: DR)

A complication of diabetes that damages the blood vessels of the retina, potentially causing vision loss ranging from mild blurriness to complete blindness. Diabetic retinopathy can produce scattered and varied patterns of vision loss across the visual field, making it distinct…

Dynamic Type(also: Dynamic Text Size, Text Scaling, Font Scaling)

An iOS accessibility feature that allows users to adjust the system-wide text size to meet their reading needs, from very small to very large. Apps that support Dynamic Type automatically reflow and resize their text content when the user changes their preferred text size in…

E-Ink Display(also: Electronic Ink, E-Paper, Electronic Paper Display)

A display technology that mimics the appearance of ink on paper by using electrically charged particles to create images. E-ink displays are characterized by high readability in direct light, minimal glare, extremely low power consumption, and reduced eye strain compared to…

Eccentric Viewing(also: Eccentric Fixation)

A visual strategy used by people with central vision loss (such as from macular degeneration) in which they learn to use a peripheral area of the retina — called a preferred retinal locus (PRL) — to look at objects instead of the damaged central macula. Eccentric viewing…

Eccentric viewing(also: Preferred retinal locus, PRL)

A viewing strategy used by people with central vision loss (such as from macular degeneration) in which they learn to look slightly off-center to use a healthier area of the retina instead of the damaged macula. The part of the retina they train themselves to use is called the…

Edge enhancement(also: Edge detection, Contour enhancement)

An image processing technique that identifies and highlights the boundaries between objects in a visual scene, typically rendering them as bright lines against a dark background or overlaying them on the original image. For people with low vision, edge enhancement can make…

Field of View(also: FoV, Viewing Angle)

The angular extent of the observable world visible at any given moment. In the context of head-mounted displays like the HoloLens 2, the field of view refers to the area in which virtual content can be displayed, which is typically narrower than natural human vision. This…

Fisheye View(also: Fisheye Lens, Graphical Fisheye)

A focus+context visualization technique, introduced by Furnas, that magnifies a region of interest while progressively compressing surrounding context — analogous to a fisheye camera lens. Used in tree visualizations, menus, and graphs to help users see detail and structure…

Focus+Context(also: Focus plus Context, Focus and Context)

A visualization interaction paradigm that integrates a detailed focus region and its surrounding context into a single unified view, rather than separating them. Techniques include fisheye views, semantic zooming, and lenses that distort or overlay content so users can see fine…

Functional Vision(also: Functional Visual Ability)

How well a person uses their residual vision to perform routine tasks under various conditions throughout the day. Functional vision goes beyond clinical measures like visual acuity to assess practical visual ability in real-world contexts — such as reading, identifying objects,…

Gaze Tracking(also: Eye Tracking, Eye Gaze Tracking)

Technology that measures and records eye movements to determine where a person is looking, for how long, and in what pattern. In low-vision research and rehabilitation, gaze tracking can reveal visual strategies such as fixation patterns, saccade paths, and preferred retinal…

Glare(also: Visual Glare)

Excessive brightness or reflections from surfaces or light sources that cause visual discomfort, reduce visibility, or impair the ability to see clearly. Glare is a significant accessibility barrier for people with low vision and light sensitivity. In musical performance…

Glaucoma

A group of eye diseases that damage the optic nerve, usually caused by abnormally high intraocular pressure. It is one of the leading causes of irreversible blindness worldwide, affecting over 80 million people. Glaucoma typically causes gradual peripheral vision loss that may…

Glaucoma

A group of eye conditions that damage the optic nerve, typically associated with elevated intraocular pressure. Glaucoma is a leading cause of irreversible blindness worldwide. It usually causes gradual loss of peripheral vision first, which can progress to tunnel vision and…

Goldmann Perimetry(also: Goldmann Visual Field Test, Kinetic Perimetry)

Goldmann perimetry is a clinical technique for mapping the visual field — the total area a person can see while fixating on a central point. The test uses a moving stimulus of controlled size and brightness projected onto a white hemispherical bowl, with the examiner tracking…

Hand-Eye Coordination(also: Visual-Motor Coordination, Eye-Hand Coordination)

The ability to coordinate visual information with hand movements to perform tasks such as reaching, grasping, placing, and manipulating objects. For people with low vision, hand-eye coordination can be significantly affected by reduced visual acuity, contrast sensitivity, depth…

Icon Size(also: Target Size, Touch Target Size)

The physical or rendered dimensions of graphical interface elements such as icons, buttons, and interactive controls. Research consistently shows that larger icon sizes improve interaction performance for users with low vision and motor impairments. WCAG 2.1 Success Criterion…

Large Print Music(also: Enlarged Music, Large Print Notation)

Music notation that has been enlarged from standard size to improve readability for musicians with low vision. Large print music is typically created by photocopying or printing scores onto A3 or tabloid-sized paper, or by digitally enlarging PDF files. While quicker and cheaper…

Large-Print Notation(also: Large-Print Music, Enlarged Music Notation)

Sheet music that has been enlarged or reformatted with larger symbols and staves to improve readability for people with low vision. Large-print music notation requires a specialized conversion process and is available from only a few sources, such as select libraries. While…

Light Sensitivity(also: Photophobia, Photosensitivity)

An abnormal sensitivity to light that causes discomfort, pain, or visual disruption. Many people with low vision experience light sensitivity, which can be exacerbated by bright overhead lighting, backlit screens, glare from reflective surfaces, and high-contrast environments.…

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 Rehabilitation(also: LVR, Vision Rehabilitation)

A multidisciplinary service aimed at helping individuals with reduced vision regain functional independence in daily life. LVR combines assistive technologies, guided training sessions, and adaptive strategies tailored to each person's visual abilities and needs. Programs…

Low-Vision Therapist(also: LVT, Low-Vision Specialist, Vision Rehabilitation Therapist)

A certified professional who works with people with low vision to develop adaptive strategies for daily living, optimize use of residual vision, and provide training with assistive devices. LVTs are part of a multidisciplinary rehabilitation team that may include…

MAGic

A screen magnification software program developed by Freedom Scientific that enlarges on-screen content and enhances visibility for people with low vision. MAGic can magnify the screen up to 36x, offers multiple viewing modes (full screen, lens, split screen), includes color…

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

A progressive eye condition that damages the macula — the central part of the retina responsible for sharp, detailed vision — leading to loss of central vision while peripheral vision typically remains intact. Age-related macular degeneration is the leading cause of severe…

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 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(also: Screen Magnification, Visual Magnification)

The enlargement of visual content to make it more readable for people with low vision. Magnification can be achieved through optical means (magnifying glasses, telescope magnifiers), electronic means (screen magnifiers, CCTV), or digital means (software zoom, pinch-to-zoom).…

Magnification Factor(also: Zoom Level, Magnification Level, Zoom Factor)

The ratio by which screen content is enlarged when using a screen magnifier. A magnification factor of 2x means the content appears twice its original size, but only one quarter of the original screen area is visible at any given time. Choosing an appropriate magnification…

Modified Stave Notation(also: MSN)

A system for adapting standard Western music notation to meet the individual visual needs of musicians with low vision. Unlike simple enlargement (large print music), MSN involves tailored modifications such as adjusting spacing between notes and stave lines, changing font sizes…

Monocular(also: Handheld Monocular, Bioptic Telescope)

A small, handheld or head-mounted telescope used by people with low vision to magnify distant objects. Monoculars are commonly used in educational settings to view chalkboards, whiteboards, and projected presentations from a distance. While effective for far-sight tasks,…

National Library Service(also: NLS, National Library Service for the Blind and Print Disabled)

A program of the Library of Congress in the United States that provides Braille and audio materials to eligible borrowers who are blind, have low vision, or have physical disabilities that prevent them from reading standard print. The NLS operates through a network of regional…

Note-Taking(also: Classroom Note-Taking)

The process of recording information during lectures, meetings, or presentations. In education, note-taking is an active learning strategy that helps students stay focused, cognitively process material, and retain information — benefits that occur even if notes are never…