A

Accommodation

Automatic adjustment to the shape of the lens of the eye in order to bring objects into focus as the viewing distance varies.

Achromatopsia

Rare, inherited vision disorder in which a person has little or no ability to see color. People with achromatopsia also commonly experience some vision loss, especially in bright light, to which they are extremely sensitive. The severity of achromatopsia varies. Although there is no cure or treatment for this disorder, people with achromatopsia can manage its symptoms. For example, they can wear sunglasses or tinted contact lenses to cope with bright light. They can use magnifiers and other devices for low vision to help them read, and telescopes to help them see distant objects.

Visual agnosia

Decreased or absent ability to visually recognize or identify shapes, objects or people.

 

Agnosia

A visual-cognitive disorder characterized by inability to recognize and identify familiar visual stimuli (objects, faces, letters, places, etc.) by vision only, despite sufficiently available visual and cognitive capacities. (This term does

not apply to difficulties with assigning labels/names to visual stimuli (Visual anomia).

 

Akinetopsia

A condition in which the individual can only see things when they are not moving.

 

Alexia

Difficulty in the naming of letters or words.

 

Amblyopia

Impaired vision in one or both eyes, with no anatomical cause, due to the impaired development of vision as a sequel to untreated optical (refractive) errors, impaired image formation due to an eye disorder such as cataract, or impaired eye alignment (strabismus). Also known as a lazy eye.

 

Anisometropia

Difference in refractive errors between the two eyes.

 

Anomia

Inability to name objects or to recognize the written or spoken names of objects.

 

Anopia

A defect into the visual field.

 

Anosognosia

Lack of awareness of and insight into an obvious functional impairment because the subject is unable to detect the mismatch between assumed/expected function and the real functional status. Anosognosia typically occurs in about 30% of subjects with hemiplegia and (visual) neglect (mainly after right-hemisphere injury) or homonymous hemianopia (irrespective of the side of brain injury).

 

Aphakia

Is due to surgical removal of the lens, because of cataract. Ahpakia is corrected either by using intraocular lenses, contact lenses or cataract spectacles.

 

Apraxia

Difficulty performing learned purposeful actions despite the requisite physical capacity. This can affect simple movements (e.g. gestures) on command after verbal instruction or by imitation (ideomotor apraxia) or complex movements (e.g. preparing a cup of tea, dressing) (ideational apraxia). The latter form is explained as loss of the action plan (impairment of Procedural memory).

 

Apraxia of gaze

Disorder of the attention due to the bilateral damage to the posterior parietal (dorsal stream) territory of the brain, leading to lack of movements.

 

Assessment

Evaluation of functioning i.e. more than the measurement of a few functions.

 

Astigmatism

A type of refractive error that focuses light at different points in front of or behind the retina rather than a single point, and results in blurred vision at all distances, due to the subtle asymmetric, non-spherical shape of the cornea.

 

Atrophy

Loss of the tissue due to wasting.

 

B

Balint´s syndrome

Results from bilateral posterior parietal injury and associated disconnection of fronto-parietal fiber tracts. A neuropsychological condition characterized by marked limitation in the number of entities that can be seen at the same time leading to restriction of the Field of attention, Oculomotor (ocular) apraxia and Optic ataxia. The syndrome can vary in severity from mild to severe; the resulting impairments are omission of parts of the surroundings, difficulties with intentionally shifting gaze to locations of interest or to external stimuli and impaired visual guidance of grasping movements and movement of other parts of the body. In addition, those affected exhibit Spatial disorientation and have difficulties with reading, writing, copying, dressing, etc.

Binocular coordination

Use of both eyes together so that the separate images from each eye (which are slightly different) are interpreted by the brain as a single image. At its highest form - stereopsis - an impression of depth can be obtained by the brain superimposing two slightly dissimilar pictures of the same objects.

 

Blindness

Absence of vision. Total blindness is complete absence of vision and is rare.

 

Blindsight

Slight awareness of, or reflex reaction to, moving targets, lights and colors in an area of apparently absent visual field.

 

Brain plasticity

The capacity of the brain to adapt its functions to altered environmental (or task) conditions by experience (Environment-dependent plasticity) and Learning (Practice-dependent plasticity) and to compensate for functional alterations of the brain, e.g. after injury or in pathophysiological states (Functional compensation).

 

Brain ventricles

Fluid filled cavities in the middle of the brain. The nerve fibers of the optic radiation run close to the wall of the lateral ventricle and are thus vulnerable if there are circulatory disturbances in the highly vascular ventricles walls.

 

Brain stem

The area at the base of the brain that, along with the midbrain above it, carries the nerves fibers running in both directions between the brain and the body and receives and processes input from the cranial nerves, including those that serve hearing and eye movements.

 

Brodmann area

Is a region of the Cerebral cortex, which is defined by its structure and organization of cells (so-called cytoarchitecture). Brodmann areas were originally defined and numbered by the German neuroanatomist Korbinian Brodmann who in 1909 described 47 different cortical areas.

 

C

Central acuity

The capacity of the visual system to see in the central visual field.

 

Central fixation target

A target placed in the center of a visual field test.

 

Cerebellum

A timekeeping brain structure that ensures that control of emotion by the frontal lobes, movement of the body processed by the parietal lobes, and vision processed by the occipital lobes are synchronized and coordinated.

 

Cerebral blindness

Profound impairment or absence of vision due to bilateral damage to the visual pathways posterior to the lateral geniculate bodies that may be accompanied by damage to other regions of the brain that serve vision. Also known as cortical blindness.

Cerebral cortex

The layer of grey matter that covers the outside of the brain and consists of six layers of neurons. Regional differences in the cytoarchitectonic characteristics led Brodmann to the categorization of the cerebral cortex into distinct areas (Brodmann’s areas).

 

Cerebral hypoxia

Lack of oxygen supply to the brain, which can be brought about by impaired blood flow or impaired oxygenation due to severe respiratory disorders.

Cerebral palsy

Loss or impairment of motor function caused by damage or abnormal development of the brain before, during or immediately after birth.

 

Cerebral visual impairment (CVI)

Visual impairment due to the damage or disorder of the visual pathways and visual centers in the brain, including pathways serving visual perception, cognition, and visual guidance of movement.

 

Chiasma

Chiasma means crossing. In anatomy it means crossing of the optic nerves.

 

Color deficiency

Inherited non-progressive condition in which the person confuses colors either in red-green or blue-yellow axis.

 

Cognitive visual dysfunction

Disordered function of the brain related to the damage of the visual-associative areas and / or their incoming pathways leading to misinterpretation of the visual world either with respect to where things are or what they are.

 

Cone cells

One type of sensory cells in the outermost layer of the retina. Cone cells are numerous in the central retina (fovea). They function in daylight and twilight, absorb light energy and produce the reactions that leads to perception of colors. They do not function in scotopic condition.

 

Color anomia

Inability to name colors due to the neurological dysfunctions.

 

Congenital

Existing at or before birth.

Contrast

The way that a foreground (an object) stands out from its background. Contrast is not a property of visual edges on the retina but of visual edges in space. This is important in allowing us to vary the learner’s visual world in order to enhance contrast.

 

Contrast sensitivity

The ability of the visual system to distinguish the difference in brightness between two adjacent surfaces.

 

Convergence

The ability to turn the eyes inward as an object approaches them.

 

Cortical

Pertaining to the cerebral cortex.

 

Crowding

Vision is sometimes worse when crowded by other information e.g. words on the page too close together or patterns behind an object. Children can be assessed for crowding difficulties with different tests and tools.

 

D

Dark adaptation

Refers to the gain in sensitivity as the eye remains in the dark. It is a relatively slow process, taking around 40 minutes to complete. Where the ability of the eyes to adapt to the dark is slower, this is likely to be associated with poorer contrast sensitivity. Should the learner suddenly exhibit poorer dark adaptation than is usual for that learner, you may want to request further examination.

 

Detection acuity

It measures what is the smallest object that a child notices on a contrasting background.

 

Developmental age

A measure of a child´s level of development according to social, emotional, intellectual and physical growth.

 

Developmental disability

Mental of physical disability arising as a consequence of a disorder of development.

 

Diplegia

Paralysis or weakness of the lower limbs.

 

Dorsal stream

The pathway between the occipital and posterior parietal lobes that maps surroundings and brings about visual guidance of movement. Sometimes known as the “where” pathway, it functions at a subconscious level.

 

Dorsal stream dysfunction

Condition in which the function of the dorsal stream is disrupted, causing impaired visual guidance of movement and limiting the number of entities that can be seen in crowed scenes.

 

Dyskinetopsia

A condition in which impaired perception of movement is relative and not absolute.

 

Dyslexia

A language-based learning disability that can be associated with difficulties in reading, spelling, writing and sound-symbol association.

E

Eccentric viewing

Looking slightly above, below or to one side of an object in order to place a visual image onto an optimum area of the visual field of viewing.

 

Electroencephalography (EEG)

Along with its magnetic counterpart, magnetoencephalography (MEG), this procedure noninvasively records brain activity from the surface of the scalp to provide an indirect evaluation of the brain function.

 

Emmetropia

Condition in which the light coming from a distant object to the eye is focused accurately on the retina to make a crisp, focused image without the need for refractive correction.

Encephalopathy

Disorder of the brain due to disease, causing damage and malfunction.

 

Epilepsy

A group of conditions in which disturbance of the electrical activity of the brain results in impairment and disorder in a range of brain functions, including consciousness, movement, sensation and vision.

 

Esotropia

A condition in which one eye is horizontally turned inward; also known as convergent strabismus (US) or convergent squint (UK). Results in a lack of stereopsis.

 

Executive functions

Higher-order mental skills that are used to control and coordinate cognitive abilities and behaviors to achieve a particular goal.

 

Exotropia

A condition in which one eye is horizontally turned outward; also known as divergent strabismus (US) or divergent squint (UK). Results in lack of stereopsis.

 

Extrastriate visual areas

Visual cortical areas outside the Striate (primary) visual cortex; also called prestriate cortex or visual association areas.

 

F

Face recognition

The identification of an individual’s face on the basis of specific and characteristic facial features, enabled by repeated identification of the same face.

 

Figure-ground discrimination

The ability to discriminate an object from its surroundings; also called figure-ground perception.

 

Fixation

The ability to maintain the eyes focused on a target.

 

Form perception

The ability to judge the shape, size, texture, etc. of an object by vision or touch; also called form discrimination.

 

Fovea

The functional centre of the retina with the most numerous and tightly packed cone cells. This gives the sharpest vision.

 

Frontal lobes

Areas of the front of the brain, part of which (the prefrontal cortex on both sides, and the front portion of the frontal lobes) serves the executive functions of thinking, planning and controlling behaviors.

 

Functional skills

Skills that students with multiple disabilities learn that provide them with the opportunity to work, play, socialize and take care of personal needs to the highest attainable level.

Functional vision

The way in which a person uses available visual skills and abilities in typical tasks of daily life. How well an individual processes the visual information in his or her environment in order to go about daily tasks.

Functional visual impairment

Damage to the visual system that impedes the ability to learn or perform usual tasks of daily life, given a child’s level of maturity and cultural environment.

 

G

Gaze apraxia

Is the impairment in using eye movements in a purposeful action, despite the intact capacity to carry out the eye movements.

 

Gestalt

Immediate mental construct of an overall (global) scenario formed from a collection of separate elements.

 

Grating

A stimulus that consists of regular parallel light and dark elements.

 

Gross motor

Movement that involves the large muscles of the body such as those in the arms and legs (e.g. crawling, running, or jumping).

 

H

Hemianopia

Lack of perception of one half of the visual field.

 

Hemifield

One half of a sensory field.

 

Hemiparesis

Weakness on one side of the body.

 

Hemiplegic

Paralysis of one side of the body.

 

Higher visual functions

The combination of visual perception, visual cognition, guidance of movement and the capacity to choose to give visual attention.

 

Homonymous hemianopia

A visual field defect which the same half of the field of view is not see by each eye.

 

Hydrocephalus

A condition due to the impaired of the circulation of the cerebral spinal fluid (CSF), causing increased intracranial pressure, commonly with increased CSF volume expanding the water spaces in the brain (ventricles).

 

Hyperopia or hypermetropia

A type of refractive error that results in blurred images when the length of the eye from front to back is too short, or the optical power of the eye is insufficient to bring an object into focus. Also known as long-sightedness or farsightedness.

 

Hypertropia

An upward eye turn.

Hypoplasia

Underdevelopment of the body part.

 

Hypoxia

Lack of oxygen.

I

Impaired pursuit

Disordered ability to pursue a moving target with the eyes.

 

Intermittent deviation

Turning of both eyes together in one direction for a variable duration, often with an accompanying head turn. Also paroxysmal deviation.

 

Ischemia

Insufficient supply of the blood.

J

Joint attention

An exchange that involves a child´s and a partner’s awareness of the other´s mutual gaze, gesture or language.

 

L

Labyrinthine system

The subconscious automatic system in the inner ear and brain stem that is responsible for controlling and maintaining the balance.

Landmark

Is a recognizable natural or man-made feature used for navigation.

 

Lateral geniculate body

Small knee-shaped structure deep inside the brain that act as relay stations to convey visual information from the eyes through the brain.

Letter agnosia

Is a selective type of visual agnosia, which is characterized by the loss of recognition of the significance of letters and/or the integration of letters into words.

Light adaptation

Is the capacity of the retina to adapt to increased levels of illumination.

Literal alexia

Inability to recognize certain individual letters due to damage to the brain.

Low vision

Visual impairment that is severe enough to impede the person´s ability to learn or perform usual tasks of daily life but still allows some functionally useful visual discrimination. It covers a range from mild to severe visual impairment, but exclude total blindness.

 

M

Magnetic resonance imagining (MRI)

A neuroimaging procedure that shows the anatomical features of the brain in great detail and can be used to study brain structure following injury.

Magnocellular pathway

A major pathway of the visual system that primarily transmits visual information in the peripheral visual field to the brain and serves movement perception, as well as facilitating visual guidance of movement.

MDVI – Multiple disabled visually impaired

There is no universally agreed definition of MDVI. As such, there are many different interpretations of the needs of those falling under MDVI. Whilst the network totally agrees with the ICF framework, MDVI Euronet partners have agreed a working definition of: 'A person with at least two disabilities, one of which manifests itself as a visual impairment, which impact significantly on the person's learning potential to such a degree so as to require a customised educational provision.'

 

Midline

The median plane of the body.

Mirror neuron system (MNS)

A system in the brain that facilitate understanding and imitation of the actions of others.

Motion perception

The capacity to see the movement.

 

Myopia

A type of refractive error that results in blurred images of the retina when viewing objects in the distance. Also known as nearsightedness or short-sightedness.

 

N

Neglect

Attentional defect, an inability to direct attention, which prevents a person of being aware of part of space around or a part of herself. It may mean loss of attention in one half of the visual field (most often on the left side).

 

Neuroplasticity

Refers to adaptation of neural pathways and structures which are due to changes in behavior, environment and neural processes as well as changes resulting from injury due to learning processes.

Norm-referenced test

An assessment tool that has been standardized in a way that enables comparison of the results of test takers in relation to a group that has already taken the test.

Null point

The position of the eyes in which the oscillations of a person’s nystagmus are least. Often accompanied by a compensatory head posture.

 

Nystagmus

Unintentional or involuntary to-and-fro movement of the eyes.

 

O

Object permanence

The understanding that objects still exist when they cannot be seen, heard, touched, smelled or sensed.

 

Occipital lobes

Posterior (back) portions of the cerebral cortex in each hemisphere responsible for processing vision and sending visual information to other parts of the brain.

 

Occipitoparietal dysfunction

A disorder involving the occipital and parietal lobes of the brain, resulting in impairment of the functions of both structures.

 

Ocular alignment

A description of the position of the eyes. If the eyes are out of alignment, strabismus is present.

 

Ocular visual impairment

Visual impairment caused by a disorder of the eye or optic nerve (but not the brain).

Oculomotor apraxia

Limited ability to move the eyes fast (saccadic eye movement) from one target to another.

 

Oculomotor scanning

Use of eye movements (Saccades, Fixations) to scan the visual surrounding or a visual stimulus array (scene, object).

 

Oculomotor dysfunction

Impaired control of the eye movements leading to visual difficulties such as visual fixation or visual tracking problems, ocular alignment and impairment of accommodation.

 

Optic ataxia

Impaired accuracy of movement of limbs and body through visual space because visual guidance of movement is impaired.

 

Optic chiasm

The X-shaped structure formed by the joining up of the optic nerves, which cross and then become the optic tracts just below and leading into the brain.

 

Optic nerves

Bundle of nerve fibers (axons) from the ganglion cells of the retina. Nerves that transmit visual information from the retina of each eye to the brain.

 

Optic nerve atrophy

Atrophy means loss of functioning cells. The reason for cell damage may be infection, trauma, tumor or increased intraocular pressure.

 

Optic radiations

A collection of the nerve axons that carry information from the lateral geniculate bodies into the thalamus to the visual cortex in the occipital lobes.

 

Optic tract

Bundles of nerve fibers that emerge from the back of the optic chiasm on each side that carry visual information to the lateral geniculate body.

 

Optokinetic

Related to the eye movement.

Optokinetic nystagmus (OKN)

Reflex to and fro movement of the eyes in response to moving targets. OKN can be tested horizontally and vertically in response to moving black and white stripes or other repeating targets in the appropriate directions in front of the eyes.

 

Optometrist

A health care provider who specializes in the measurement of refractive errors and other visual functions, prescribes eyeglasses or contact lenses and (in some countries) diagnoses and manages conditions of the eye.

 

Optotypes

Letters and symbols used to test visual acuity.

 

Orientation perception

The capacity to know where one is, has been and will be going, as well as the position and location of possession.

 

Orthoptist

A specialist in measurement and management of disorders of the eye movements and binocular vision.

 

P

Parallax

The perception of the relative alignment of objects in relation to the position of viewing. A phenomenon that helps compensate for lack of stereopsis.

Parallel processing

Is the ability to simultaneously process several stimuli.

Parietal lobes

The parts of the brain that integrate incoming sensory information with the execution of body movements and process language (usually on the left side).

Parvocellular pathway

A pathway of the brain served by small retinal and brain cells that transmit fine, detailed visual information primarily in the central visual field.

Pattern perception

Is the discrimination and identification, respectively, of a set of stimuli arranged in a certain regular form, e.g. contours, figures, objects, faces, words, melodies.

 

Perception

The ability to see, hear or become aware of something through senses.

 

Perceptual visual dysfunction

A condition in which the brain is unable to process visual information correctly. Sometimes used synonymously with perceptual visual impairment.

 

Perinatal

Around the time of the birth.

Peripheral target

A target placed at the outer edge of a person´s visual field.

Peripheral visual field

The area of vision outside the center of an individual´s gaze.

Periventricular leukomalacia

Damage to the white matter adjacent to the lateral ventricles of the brain.

 

Periventricular white matter

The white matter near to the ventricles of the brain.

Photophobia

Increased sensitivity to light.

Preferential looking (PL)

Is an experimental method in developmental psychology. An infant is habituated to a particular stimulus; then a second, new stimulus is shown, which differs from the habituated stimulus with respect to a specific feature (e.g. size, color, form). If the infant now looks for longer at the new stimulus, it is suggestive that the infant can discriminate between the two stimuli. Preferential looking is now used routinely to estimate visual acuities in young children and those who are otherwise unable to cooperate with the use of other methods.

Prefrontal cerebral cortex

The anterior part of the frontal lobes of the brain that contributes to initiation and coordination of thoughts and actions.

Prematurity

Birth before 37 weeks’ gestation.

Prosopagnosia

Inability to recognize faces.

Pupil of an eye

The hole in the center of the iris that allows light to enter the eye and, by its change in size, controls the amount of light passing through.

 

Pursuit eye movements

Smooth eye movements made while following an object. Also known as smooth pursuit movements.

 

Q

Ouadrantopia

A defect in the visual field that affects a quarter of the visual field, demarcated by vertical and horizontal lines passing through the center of the visual field.

 

R

Recognition acuity

Ability to recognize and distinguish a specific visual target from other similar stimuli; often measured using letter charts.

Refractive errors

A focusing inaccuracy within the eye such the light rays do not come into clear focus on the retina, resulting in a blurred image. (In children and young adults the refractive error of hyperopia may be corrected by accommodation and therefore may not lead to a blurred image).

Rehabilitation

Training to improve skills or behaviors that have been lost or decreased due to disease or injury.

Relative orientation perception

Ability to see subtle differences between orientations.

Retina

The inner sensory nerve layer next to the choroid that lines the posterior two-thirds of the eyeball. The retina reacts to light and transmits visual information by means of nerve impulses to the brain.

Retinopathy of prematurity (ROP)

A disorder of the retina related to abnormal vascular development that occurs as a sequel to premature birth. It is arrested in most cases following appropriate screening and treatment.

Rod cells

Sensory cells in the outer layer of the retina. They are highly sensitive to light and thus function best in twilight and scotopic conditions. In daylight their activity is not transmitted through the retina because the function of the cone cells inhibits it. The highest concentration of rod cells is in the peripheral parts of the retina.

 

S

Saccades

Fast eye movements from one fixation to another.

Voluntary eye movements, usually quick movements of both eyes simultaneously, used for tasks such as reading or scanning a scene.

Scanning

Making a series of visual fixations in order to visually inspect a large area.

 

Scotoma

A non-seeing area in the visual field.

Simultagnosia

Inability to see more than one or two items within the visual scene at the same time due to damage to the posterior parietal region of the brain.

Spastic diplegia

A form of cerebral palsy resulting in weakness and stiffness of the lower limbs.

 

Spatial orientation

Is the perception of one’s own location in space and its adjustment with reference to objects (Landmark) in the same space.

Spatial vision

Perception of spatial properties of visual stimuli, e.g. position, orientation of contours, spatial configuration of figures, objects and scenes.

 

Stereopsis

Fine depth perception that results from the brain´s interpretation of the slight difference between the disparate pictures of the same visual scene provided by the two eyes.

Strabismus

Misalignment of the eyes; eyes do not look on the same direction.

Striate (primary) visual cortex

Is the discrete region in the posterior occipital lobes of the brain that receives input directly from the eyes via the Optic radiations, which serves primary visual functions, e.g. light detection; also labelled Brodmann area 17 or V1 (visual area 1). (When this part of the brain is sectioned, a light brown line, or stria, is observed, from which the term striate is derived).

 

Striate cortex

First cortical area which receives retinal input from the thalamus (geniculo-striate pathway); also called primary visual cortex, Brodmann’s area 17, visual area 1, V1.

 

T

Temporal lobes

The areas of the brain under the temples that analyze the input from the senses. They provide that memory banks that underpin knowledge and recognition.

Text processing

Is the act of processing text material (letters, numbers); essential prerequisites are an intact central visual field, a sufficiently high visual acuity and contrast sensitivity, accurate form discrimination, ability to integrate letters/numbers to larger elements and regular shifting of fixation in the direction of processing. Text processing is the main basis for understanding of text material.

Thalamus

A structure situated between the cerebral cortex and the midbrain involved in processing and relaying sensory and motor signals to the cerebral cortex. The thalamus plays and important part in bringing about reflex visual attention.

 

Threshold acuity

The lower limit of visual acuity measured with each eye separately for the purpose of diagnosis and follow-up of visual disorders.

 

Topographic agnosia

Disorientation in one´s surrounding. Impairments results from ventral stream damage and problem forming mental map of the environment. Also known as topographic disorientation.

 

Tracking

Maintaining fixation on a moving object of interest using pursuit eye movements.

V

Ventral stream

Visual pathway between the occipital and temporal lobes, sometimes known as the “what” pathway, which supports the process of visual recognition. Dysfunction can cause impaired recognition of objects and persons and impaired orientation in surrounding and extended space.

Ventricles

Fluid-filled cavities in the brain.

Vestibular ocular reflex (VOR)

The balance system served by the inner ear accords subconscious knowledge of the vertical and horizontal; these data inform the vestibular system in the midbrain, which automatically aligns the eyes to the horizon in total darkness. Rotation of the head in an unconscious person brings about such righting (doll’s eye) movements if brainstem function is intact.

Vision loss

Lack of vision due to acquired damage to a previously intact visual system.

Visual acuity

A measure of the ability of the visual system to see or resolve the component parts of an image as being separate from one another, when tested at maximum contrast.

Visual attention

The ability to focus on specific elements in a visual scene by selecting or by being drawn salient information and filtering out less salient information.

 

Visual blurring

Is observed when discrete boundaries between image components are not seen as distinct, but instead merge into one another. This can be caused by refractive error and disorder of the eyes or visual pathways.

Visual brain

The totality of brain elements serving or supporting vision that serve to map, search, give attention to, recognize and interpret visual input.

 

Visual cognition

The capacity to process what is seen, to think about its significance, and to manipulate and use both incoming image data and remembered imagery in the context of creative thought.

Visual dysfunction

Disorder of the visual perception, visual guidance of movement, and / or visual attention.

Visual evoked potential (VEP)

Computerized recording of electrical activity at the back of the brain used assist in diagnosis and in the estimation of visual acuity and contrast sensitivity.

 

Visual field

Area of space visible to the eyes when looking straight ahead.

 

Visual functions

Measurable components of vision including visual acuity, contrast sensitivity, color perception, visual fields and the perception of movement.

 

Visual guidance of movement

Mapping of incoming visual information in the mind that is used to guide movement of the limbs and body.

 

Visual impairment

Damage to the visual system that impedes the ability to learn or perform usual tasks of daily life, given a child´s level of maturity and cultural environment. Includes both low vision and blindness.

Visual latency

The time taken to receive and process incoming visual information in the brain.

Visual guided motor behaviors

Behaviors with a major visual-motor component, including reaching for, turning toward, and moving among obstacles toward visual targets.

 

Visual memory

The ability to remember a visual image or form after viewing.

 

Visual-motor processing

Coordination of goal-directed motor actions in relation to a visual target.

 

Visual neglect

Inattention to one side of the visual space and / or to one side of the body.

 

Visual pathways

Bundles of nerve fibers that carry visual information to different location of the brain.

 

Visual perception

Ability to interpret the immediate environment by processing incoming information that is sent from the eyes to the brain.

 

Visual processing

The brain´s recognition and interpretation of information taken in through the eyes.

 

Visual recognition

The ability to recognize and identify objects, faces, geometric shapes and colors as well as their pictures and images.

 

Visual search

Is the process of detecting a target stimulus among distractor stimuli. If the target differs qualitatively from distractors, it pops out, and search time is independent of the number of stimuli in the display (set size); this search type is called a parallel search mode. If the target and distractors are similar, then the subject has to search for the target in a serial fashion (serial search mode).

 

Visual space perception

Is the sum of abilities to process and comprehend spatial properties of the environment and of objects, i.e. position, distance, direction, spatial relationships between stimuli.

 

Visual stimulation

An approach that places a child as a passive observer, in an environment in which selected visual stimuli are presented with the intention of bringing about attention and enhancement of visual development.

 

Visual system

Network that produces sight, including both the eyes and the brain.

 

Visuospatial perception

The capacity to appreciate, understand and map the three-dimensional characteristics of the surroundings, both for subjective appreciation and to facilitate movement through space.

 

W

WHAT pathway

Occipito-temporal route that is specialized for the processing of visual object properties.

 

WHERE pathway

Occipito-parietal route that is specialized for the processing of visuospatial information.

 

Working memory

Is the ability to actively process information in temporary storage, with a phonological loop for the manipulation of verbal content and a visuospatial scratch pad for retaining of visual information; the central executive coordinates these two ‘slave systems’ and deploys attentional resources between them.

 

References

 

  1. Zihl J. and Dutton G.N. 2015. Cerebral visual impairment in children. Visuoperceptive and visuocognitive disorders. Wien, Austria. Springer.

  2. Lueck A.H. and Dutton G.N. 2015. Vision and the brain: Understanding cerebrl visual impairment in children. United States of America. American Foundation for the Blind.

  3. Hyvarinen L and Jacob N. 2011. What and how does this child see? Helsinki, Finland. VISTEST Ltd.

Terminology

This webpage was supported by the Erasmus+ Programme of the European Commission.

 

This webpage reflects the views only of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained herein.

© 2015 by B&H  The National Institute for the Blind, Visually Impaired and Deafblind in Iceland