Glossary
Searchable terminology from accessibility, web standards, and related fields.
26 results found in Vision.
- Adaptive Optics (AO)
- A technology that measures and corrects optical distortions in real time, originally developed for astronomical telescopes and now applied in ophthalmology and vision science. Adaptive optics systems …
- Anomalous Trichromat (Anomalous Trichromacy, Colour Anomaly)
- A person who has all three types of cone cells in the retina but one type has a shifted spectral sensitivity, causing altered colour perception that is less severe than dichromacy. Anomalous trichroma…
- Artificial Eye (Eye Model, Optical Eye Model)
- A physical device constructed from optical components to simulate the optical properties of a human eye. Typically consisting of a lens, adjustable aperture (simulating the iris), and an image sensor …
- Color Perception (Color Vision, Chromatic Vision)
- Color perception is the ability to detect, distinguish, and identify colors. Impairments in color perception range from complete color blindness (achromatopsia) to partial deficiencies in distinguishi…
- Dichromat (Dichromacy, Dichromatic Vision)
- A person with colour vision based on only two types of functional cone cells in the retina instead of the typical three, resulting in a reduced ability to distinguish certain colours. Dichromats perce…
- Farnsworth D-15 Test (D-15 Color Test, Farnsworth Dichotomous Test)
- The Farnsworth D-15 test is a clinical assessment used to evaluate color perception by asking a person to arrange 15 colored caps in order of hue. The pattern of errors reveals the type and severity o…
- Fixation Problem (Reading Fixation Difficulty, Visual Fixation Issue)
- A difficulty in maintaining stable visual focus on a specific point or line of text during reading. People with fixation problems may lose their place frequently, skip lines, or re-read the same passa…
- Fovea (Foveal Vision, Fovea Centralis)
- The small, central area of the retina responsible for sharp, detailed vision, covering approximately 1 degree of visual angle. The fovea contains the highest density of cone photoreceptors and provide…
- Goldmann Perimetry (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 brig…
- Image Enhancement (Image Pre-Compensation, Visual Enhancement)
- Image enhancement in the context of accessibility refers to techniques that modify digital images or on-screen content to improve their visibility and usability for people with visual impairments. Met…
- Ishihara Test (Ishihara Colour Test, Ishihara Plates)
- A widely used clinical screening test for red-green colour vision deficiencies, consisting of a series of circular plates made up of coloured dots arranged in a mosaic pattern. Each plate contains a n…
- Monochromacy (Achromatopsia, Total Color Blindness)
- The rarest and most severe form of color vision deficiency, in which an individual has complete or near-complete absence of color perception, seeing the world only in shades of gray. Monochromacy occu…
- Near Visual Acuity (NVA, Near Acuity)
- A measure of the eye's ability to resolve fine detail at a close distance, typically tested at 40 centimetres. Near visual acuity is particularly important for tasks involving reading, handheld device…
- Ocular Aberration (Optical Aberration, Wavefront Aberration)
- Ocular aberration refers to deviations in the way light is focused by the optical components of the eye (cornea and lens) compared to an ideal optical system. These aberrations distort the image forme…
- Pelli-Robson Chart (Pelli-Robson Contrast Sensitivity Chart)
- The Pelli-Robson chart is a clinical tool used to measure contrast sensitivity — the ability to detect objects at low-to-moderate contrast levels. The chart consists of a series of letter-charts compo…
- Point Spread Function (PSF)
- A mathematical description of how a single point of light is spread or blurred by an optical system such as the human eye. The point spread function characterizes the degree and pattern of distortion …
- Pupil Diameter (Pupil Size, Aperture Size)
- The width of the opening in the iris through which light enters the eye, typically ranging from about 2mm in bright light to 8mm in darkness. Pupil diameter significantly affects visual quality becaus…
- Refractive Error (Refractive Disorder, Ametropia)
- Refractive error is a common vision condition in which the shape of the eye prevents light from focusing correctly on the retina, resulting in blurred vision. Types include myopia (nearsightedness), h…
- Scotopic Sensitivity (Irlen Syndrome, Visual Stress, Meares-Irlen Syndrome)
- A visual-perceptual condition in which certain wavelengths of light cause discomfort, distortion, or difficulty when reading. People with scotopic sensitivity may experience text appearing to shimmer,…
- Simultaneous Color Contrast (Simultaneous Contrast)
- A perceptual phenomenon where the appearance of a colour is influenced by the colours surrounding it, causing the same colour to look different when placed against different backgrounds. For example, …