ACVREP CLVT key terms

The sharpness of vision measured with the person's optimal refractive correction in place, expressed as a Snellen or logMAR value for each eye and both eyes together.

A notation for acuity written as a ratio, such as 20/200, comparing the distance at which a person identifies a letter with the distance a standard observer would identify it.

A logarithmic scale for acuity in which each line of letters changes by 0.1 log units, allowing precise averaging and statistical comparison of measurements across visits.

Visual resolution measured at a close working distance, typically 40 cm, recorded in M-units or point size and used to judge reading print size needs.

A metric for print size in which one M-unit equals the size of letters subtended at one meter by five minutes of arc; used to specify required magnification for reading.

A graph of the minimum contrast needed to detect gratings across a range of spatial frequencies, revealing how well a person sees large, faint, and fine targets.

The ability to distinguish an object from its background when the two differ mainly in luminance rather than in size, important for mobility, facial recognition, and reading low-contrast text.

A wall-mounted test of letter contrast sensitivity in which triplets of letters decrease in contrast, yielding a single log contrast sensitivity score.

Reduced visual performance caused by stray light from a bright source, measured with glare tests and often reported by clients as washout or discomfort in bright settings.

The total area a person can see without moving the eyes or head, commonly mapped by perimetry and described in terms of extent, sensitivity, and defects.

Systematic measurement of visual field sensitivity, using static or kinetic methods, to map areas of normal, reduced, and absent vision.

A localized area of reduced or absent vision within the visual field, which may be central, paracentral, or peripheral and may be absolute or relative.

Loss of vision in one half of the visual field of each eye, typically from a post-chiasmal lesion, affecting the same side in both eyes.

Absence of vision in the macular region, which impairs reading, face recognition, and fine detail tasks and often prompts use of a preferred retinal locus.

A retinal area outside the fovea that a person with central field loss habitually uses to fixate, sometimes trained deliberately to improve reading and spotting.

A trained technique of directing gaze slightly away from a target so that images fall on healthy retina adjacent to a central scotoma.

Reduced ability to discriminate hues, most often inherited red-green loss, which can affect color-coded tasks, signal identification, and some occupational requirements.

A set of pseudoisochromatic plates in which numbers or pathways are hidden in dot patterns, used to screen for red-green color vision deficiency.

Depth perception arising from the slight difference between the images received by the two eyes, tested with random-dot or contour stereotests.

Cognitive processes that interpret visual input, including discrimination, spatial relations, figure-ground, closure, and visual memory, assessed to explain functional difficulties beyond acuity.

The coordination of visual perception with hand movement to copy, draw, or manipulate objects, evaluated when handwriting or fine motor tasks are affected.

A attention-related failure to respond to stimuli on one side of space despite intact visual pathways, often after right hemisphere injury and distinct from hemianopia.

A structured evaluation of how a person uses remaining vision in real environments and tasks, combining clinical data with observation to guide instruction and accommodations.

A process for determining which literacy media, such as print, braille, or both, best support a student's reading and writing based on sensory and academic data.

Visual impairment that cannot be corrected by ordinary glasses or surgery and that interferes with everyday tasks, but that may be improved with optical or nonoptical devices.

Enlargement of the retinal image achieved by relative distance, relative size, angular magnification, or electronic means to make a target resolvable.

A strong plus lens, alone or added to a distance prescription, that allows a person to hold reading material closer and thereby enlarge the retinal image.

An optical or electronic aid prescribed to improve performance on specific tasks, including magnifiers, telescopes, filters, and video magnifiers.

A plus lens mounted in a frame and held by the user, offering portability for spot reading and inspection of small details at a chosen distance.

A magnifier resting on legs or a base at a fixed distance from the page, useful for people with tremor or limited stamina because focus is maintained by the stand.

An optical system that enlarges distant objects, used hand-held for spotting or spectacle-mounted for extended viewing such as board work or television.

An electronic device that captures print or objects with a camera and displays them enlarged on a screen, offering adjustable magnification, contrast, and polarity.

A tinted lens that reduces specific wavelengths or overall light reaching the eye, used to manage glare and light sensitivity and sometimes to enhance contrast.

Abnormal intolerance of light that causes discomfort or worsening of vision in ordinary lighting, often managed with filters, hats, and lighting control.

Routine self-care tasks such as eating, dressing, bathing, grooming, and toileting, assessed to identify needed training or adaptive techniques.

Tasks needed to live independently, such as cooking, shopping, managing money, using transportation, and handling medications, often affected earlier by vision loss.

A person's subjective appraisal of physical, emotional, and social well-being, measured with vision-specific instruments to capture the impact of impairment and intervention.

The emotional and social process of adapting to vision loss, including grief, identity change, coping strategies, and use of support systems.

Devices and software that compensate for vision-related limitations, such as screen readers, screen magnification, braille displays, and optical aids, selected through task-based assessment.