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Visual perceptualDysfunctions and Assessment Made by :Gundeep SinghMOT Neurology

What is visual perception ?The ability to use vision to adapt to the environment which requires the integration of vision within the CNS to turn the raw data supplied by the retina into cognitive concepts of the perception of space and objects that can be manipulated and used for decision making .The process by which this occurs is known as visual perception .

How it works ?It occurs through visual processes

Visual processing within the CNS

RETINA : RODS AND CONES , BIPOLAR CELLS , GANGLION CELLS FROM OPTIC CHAISMA FROM OPTIC TRACT TO LATERAL GENICULATE NUCLEUS VIA GENICULO CALCARINE TRACTS TO VISUAL CORTEX

PATHWAY FROM RETINA TO LGN AND TO VISUAL CORTEX

The visual cortexis the part of the cerebral cortex responsible for processing visual information, and is located in the occipital lobe.The term visual cortex refers to the primary visual cortex (also known as striate cortex or V1) and extra striate visual cortical areas such as V2, V3, V4, and V5.

http://wiki.bethanycrane.com/introducingtheeye

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Primary cortex transmits information to two primary pathways The dorsal stream and The ventral stream.

Dorsal Stream

Thedorsal streamis associated with motion, the position of objects in the world, engagement with the environment and control of the eyes/arms (especially when visual information is used to guide saccades).

Ventral streamTheventral streamis responsible for form recognition, object representation,conscious perception of environment and is associated with Long term memory storageVisual input travels from the visual cortex through parietal and posterior temporal circuitry to the prefrontal lobe to complete cortical visual processing

Visual input travels from the visual cortex through parietal and posterior temporal circuitry to the prefrontal lobe to complete cortical visual processing 7

COMPONENTS OF VISUAL PERCEPTUAL PROCESSING visual perceptual processing can be defined in a hierarchical model. It consist of process of visual cognition , visual memory, pattern recognition, visual scanning and visual attention .

These are also called as foundation skills 8

Hierarchical model of visual perceptual processing

The highest order visual perceptual process in the hierarchy is visual cognition.These perceptual processes are supported by three basic visual function that forms the foundation of the hierarchy : Oculomotor Control,Visual Fields ,Visual AcuityVisual cognition : It is a ability to manipulate and integrate visual inputs with other sensory information to gain knowledge, solve problems, formulate plans , and make decisions.( For the complete cognitive processing)

For example10

For example Adult standing at a distance.

Visual memory Visual memory : visual cognition cannot occur without the presence of visual memory. The mental manipulation of visual stimuli requires the ability to create and retain a picture of the object in the minds eye while the visual analysis is being completed.

Before the visual image can be stored in memory , and individual must recognize the pattern making up the image .Pattern recognition, which sub-serves visual memory in the hierarchy , it involves identifying the object from the surroundings. A salient feature is one that distinguishes a particular object from another .Pattern Recognition

For example E FT LGreen apple and red apple

To see its general shape, contour and features like color, shading, and texture .

Pattern recognition can not be accomplished without the next process in the hierarchy : visual scanning : It is accomplished through the use of saccadic eye movements . A saccade is a movement of the eye towards an object of interest in the environment .

Visual attention Visual scanning is actually a product of visual attention .Visual search occurs on two levels : An automatic or reflexive level- (controlled by brain stem) Any novel object moving or sudden appearing in the peripheral visual field, such as a flash of light. This response serves to protect an individual from unexpected intrusions in the environment.A voluntary level- (directed by the cortex), is complete for the explicit purpose of gathering information .

Reflexive level brain stem Voluntary level cortical process of cognition .16

Visual attention Visual attention is a critical prerequisite for visual cognitive processing If and how a person attends to an object or information determines if and how that visual input is analyzed by the CNS, which becomes the basis for decision making . People who do not attend to visual information do not initiate a search for visual information , do not complete pattern recognition , do not lay down a visual memory and cannot use this visual input for decision making .

Engagement of visual attention and the other higher level processes in the hierarchy cannot occur unless the CNS is receiving clear, concise visual information from the environment .Visual input is provided through the visual functions of oculomotor control, visual fields and visual acuity.

Oculomotor control : It enables eye movement to be completed quickly and accurately and ensures perceptual stability . Visual fields : Which lets the brain know what's going on in the environment .Visual acuity : Ensures that the visual information sent to brain is accurate.

VISUAL PERCEPTUAL DYSFUNCTIONS AND ASSESSMENT

Disorders of visual perception are found in :

Stroke Intracranial compressing massesNeurosurgical proceduresDemyelinating disorders Neurodevelopmental conditions (eg, autism)Neurodegenerative disease Schizophrenia and depression.

Purpose of the assessment To identify the limitation in activity or occupation.To link that limitation to presence of a visual impairmentTo develop an appropriate intervention plan based on the results of the assessment .

Occupational therapy assessment of specific visual perceptual impairmentsVisual acuity : It is commonly measured by Snellen fraction.Normally :( 20/20) it means that a person can see the letter that a person with normal vision can see at 20 feet.The common Defects of visual acuity are :Myopia(nearsightedness),Hyperopia(farsightedness)

3. Astigmatism- Itis an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina.

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Assessed by : LeaNumbers low vision test chart and warren text card

Visual field Visual field defect is caused due to damage to the receptor cells in the retina optic pathway that relays retinal information to CNS for processing results in a visual field deficits . Conditions occuring in VFD are :Heminanopsia : There has been loss of vision in one half of the visual fields in the eyes.Homonymous : it means deficit is same in both the eyes.The assessment of the VF is know as perimetry test these ranges from simple confrontation test to more precise imaging of a scanning laser opthalmoscope (SLO).

Visual field defects

Screening of visual field deficits Confrontation testing Equipments: eye patch or patches Set up : patient seated directly opposite to examiner, approx 20 inches eye to eye .Background behind examiner should be dark and distraction free.Procedure : patch the patient left eye and close or patch your own right eye Instruct patient to look at your left eye and tell him or her you will be moving a target in from the side and the patient is to indicate when the target is first seen.

Move target in from all angles Compare the patient response with yours.Position hands at 3 and 9 clock so that you can just see your fingers . Ask the patient how many fingers you are holding up .A problem is indicated if the patient cannot see the target when you do or does not see both fingers simultaneously.

Visual skills for reading test provides an effective way to measure the interference of the VFD on reading performance.Perimetry devices such as the Damato 30 point multifixation campimeter ( biVABA).

http://www.sussexvision.co.uk/damato-fieldscreener-30-point-p-5638.html

Visual attention and scanning Condition which occurs due to defect of VA and scanning are :Hemi- inattention : Instead of initiating from left to right visual search pattern, clients with right hemisphere injuries often begin and confine search to right side .Visual neglect : it is a combination of hemi- inattention and left visual field defect (VFD).clients with this condition show exaggerated inattention towards the left half of the visual space surrounding the body and often do not move the eye past midline towards the left or turn head towards the left side .

Unilateral neglectHemispatial neglect, also called hemiagnosia, hemineglect, unilateral neglect, spatial neglect, unilateral visual inattention, hemi-inattention or neglect syndrome is a neuropsychological condition in which, after damage to one hemisphere of the brain is sustained, a deficit in attention to and awareness of one side of space is observed. It is defined by the inability of a person to process and perceive stimuli on one side of the body or environment that is not due to a lack of sensation.

Unsworth, C. A. (2007). Cognitive and Perceptual Dysfunction. In T. J. Schmitz & S. B. OSullivan (Eds.), Physical Rehabilitation (pp. 1149-1185). Philadelphia, F.A: Davis Company.

Spatial neglect may result from lesions of the dominant parietal, temporal, or frontal cortex.There are different types of unilateral neglect:(Eskes & Butler, 2001) Personal neglectPeri-personal neglectExtra-personal neglect

Brain Imaging Studies

Assessment Assessment of lower level visual functions ( visual acuity , oculomotor function and visual field).Letter cancellation test Trail making Brain injury visual assessment battery for adults.(Other specific scales are to be discussed later on)

Scan board test Described by warren Consist of large 20 by 30 inch board with a series of 10 numbers displayed in an unstructured pattern .The board is placed at the eye level and centered at the clients midline .The client is asked to scan the board Point out all of the numbers that are seen.The examiner records the pattern the client follows .

Visual field defect Hemi-inattention Search pattern is abbreviated toward blind fieldsSearch pattern is asymmetrical: initiated/confined to the right sideAttempts to direct search towards blind sideNo attempt to direct search toward left sideSearch pattern is organized and generally efficient Search pattern is random and generally inefficientClients rescans to check accuracy of performanceClient does not rescan to check accuracy of performanceTime spend on task is appropriate to level of difficultyClient completes task quickly; level of efforts applied is not consistent with difficulty of task

Comparision of search pattern : person with visual field defect vs hemi- inattentionFrom Warren M:Brain injury visual Assessment battery

Occulomotor function deficit Deficit in oculomotor control following brain injury generally results from either of two types of disruption Specific cranial nerve Disruption of central neural control of the extra ocular muscles affecting the coordination of eye movements .

Oculo motor functionThe defects is associated with cranial nerve injury .Oculomotor nerve (3): impaired vertical eye movements , lateral diplopia for near vision tasks, dilation of pupil and impaired accomodation , ptosis of eyelid.Trochlear nerve (4) : impaired downward and lateral eye movements, vertical diplopia for near vision tasks Abducence nerve (6) : impaired lateral eye movements, lateral diplopia for far vision tasks.

Assessment of oculomotor function Ask the client about the expercience of diplopia :Look for the diplopia disappering when eye closed Which side lateral or vertical Far or near The next part of the assessment is observing the client eye and eye movement for deficiencies The eye are observed for asymmetries in pupil size , eyelid function and eye position as the client focuses on a distance object .

Look for ptosis Tracking of the moving object : in figure of H or X pattern Note the point of convergence ( normally approx 3 inches from the bridge of nose ).Eye ball movement

Assessment of specific visual perceptual impairments Visual object Agnosia : caused due to lesion to the right occipital lobe . In this the person is unable to recognize and identify an item using visual means.Assessment is performed by asking the individual to identify five common objects by sight.Color agnosia : Refers to inability to remember and recognize the specific colors for common objects in the environment. Also know as Central AchromatopsiaAssessment : present the client with two common objects that are accurately colored and two objects that are not accurately colored . Ask the patient to pick the object that are not accurately colored.Color Anomia: refers to the clients inability to name the color of the object. while the client understand the differences between the different colors of objects, they are unable to name the color of the object accurately .

Caused due to lesion in the right occipital lobe or posterior multimodal association area 41

Color anomia : ask the client to name the color of various objects in their environment .Metamorphopsia : refers to visual distortion of objects, such as the physical properties of size and weight .Assessment includes presenting the client with various objects of different weights and sizes.Prosopagnosia : refers to an inability to recognize and identify familiar faces caused due to lesion of the right posterior hemisphere . Non standardized test : to identify the names of the people in photographs, with family members

Prosopagnosia : the indv. May have difficulty recognizing his or her own face, faces of family members and friends, famous individuals .bcoz they cannot recognize the unique facial expressions that make each face different .42

Simultanognosia : refers to the inability to recognize and interpret a visual array as a whole and is caused by lesion to the right hemisphere of the brain .The person is able to identify the individuals components of a visual scene , but are unable to recognize and interpret the gestalt of the scene .Assessment : presenting the client a photograph of a detailed visual array .

Right left discrimination :

It is the inability to identify the right and left sides of ones own body or of that of the examiner .The person with right and left discrimination cannot tell the therapist which is the right arm and which is the left . It is caused due to lesion at the parietal lobe of either hemisphere Testing : ask the person to point to body part on command, such as : right ear, left foot, right arm.

Visual-spatial perception Disorders

It refers to appreciate the spatial arrangement of ones body, objects in relationship to oneself, and relationship between objects in space.Figure-ground discrimination: it is a inability to visually disctinguish a figure from the backgroung in which it is embedded.The patient cannot locate items in a pocketbook or drawer, locate buttons on a shirt. It is caused due to parieto-occipital lesion of the right hemisphere and less frequently the left hemisphere commonly produce this disorder.It can be assessed functionally in a variety of contexts . During a dressing activity, or by asking in the client to pick one utensil out of many utensils .The Ayres Figure-ground Test( subtest of the southern California sensory integration tests)

Form discriminationForm discrimination : It is inability to perceive or attend to subtle difference in form and shape . The patient is likely to confuse objects of similar shape or not to recognize an object placed in a unusual position.It is caused due to lesion at the parieto-temporo-occipital region of the non-dominant lobe.Testing : A number of items similar in shape and different in size are gathered. The patient is asked to identify them. Visual agnosia must be ruled out first.

Spatial RelationsSpatial disorientation, is the inability to perceive the relationship of one object in space to another object, or to oneself. It is caused due to lesion to the inferior parietal lobe Testing : The patient may be unable to tell the time from a clock because of difficulty in perceiving the relative positions of the hands. Before testing unilateral neglect and hemianopsia should be ruled out .Rivermead perceptual assessment battery(RPAB) The Arnadottir OT-ADL Neurobehavioural Evaluation

Depth perception In this the person experiences inaccurate judgment of direction, distance, and depth. Caused due to lesion in the posterior right hemisphere in the superior visual association cortices.To test the person is asked to fill a glass of water.

Position in spaceIt is inability to perceive and to interpret spatial concepts such as up, down, under, over, in, out, in front of, and behind.The lesion is usually located in the non-dominant parietal lobe.Testing : to test function, two objects are used, such as a shoe and a shoebox. The patient is asked to place the shoe in different position in relation to shoebox; for example, in the box, on top of box or next to box.

Vertical disorientation: it is the distorted perception of what is vertical . Caused due to lesion in the non-dominant parietal lobe.Test by asking the person to place the cane vertically when it is placed horizontally . Topographic disorientation: difficulty in understanding and remembering relationship of one location to another . Caused due to lesion inferior parietal lobe or occipital association cortex and occipito temporal cortex.Test by asking to describe or to draw a familiar root such as the block in which he lives .

Standardized assessment toolsToglias dynamic object search test : assess the visual processing , visual scanning , and visual attention AMPS( assessment of motor and process skills ): it evaluates the performance skills necessary for engagment in areas of occupation by assessing 16 motor skills and processing skills ( eg. Temporal oraganization , organizing space and objects )Loewenstein occupational therapy cognitive assessment ( LOTCA) and Rivermead perceptual assessment battery provide a comprehensive profile of visual perceptual and motor skills and involve both motor free and constructional functions.

A variety of other assessment tools require either a verbal or a simple pointing response . Motor-Free Visual perceptual Test revised ( MVPT-R)Assess basic visual perceptual abilities And an alternative version of the test present the multiple choice in a vertical format to reduce the interference of hemianopsia or visual inattention (MVPT-V)The Test of Visual perceptual skills upper level (TVPS-UL) Hooper visual organization testMinnesota paper Form Board Test

1. Motor-Free Visual Perception Test, Third Edition (MVPT-3)

By Ronald P. Colarusso, EdD, and Donald D. Hammill, EdDThe Motor-Free Visual Perception Test (MVPT) is a widely used, standardized test of visual perception. This measure is meant to assess visual perception independent of motor ability. It was originally developed for use with children , however it has been used extensively with adults.

Original MVPT.Contains 36 items.MVPT-R.Contains 40 items. Since theMVPT-Rincludes children up to 12 years old, four items were added to the items of theoriginal MVPTto accommodate the increased age-range covered by the norms of theMVPT-R.MVPT-3.Contains 65 items.

Time:Original MVPT and MVPT-R.The test takes 10-15 minutes to administer, and 5 minutes to score (Brown et al., 2003).Scoring:Original MVPT and MVPT-R.One point is given for each correct response. Raw scores are then converted to age and perceptual equivalents to allow for a comparison of the patient's performance to that of a normative group of same-aged peers.

The Developmental Test of Visual Perception: Second Edition (DTVP)Purpose: Measures both visual perception and visual motor integration skillsAges: 4 to 10 yearsAdministration Time: 45 minutesSubtests include:Visual-Motor Speed, Position in Space, Eye-Hand Coordination, Copying Spatial Relations, Figure-Ground, Visual Closure, Form Constancy.The subtests are grouped into two categories:Motor-Reduced Visual Perception andVisual-Motor Integration.Scoring is recorded as quotients in these areas. A General Visual Perception Quotient is also generated. The Complete Set includes Manual, Picture Book, 25 Profile/Examiner Record Forms, and 25 Response Booklets, all in a storage box.

The Test of Visual-Perceptual Skills, Third Edition:

The TVPS-3 includes the following subtests:Visual DiscriminationVisual MemoryVisual-Spatial RelationshipsForm ConstancyVisual Sequential MemoryVisual Figure-GroundVisual Closure

It Assess to determine the visual perceptual strengths and weaknesses of students.Items are presented in a multiple-choice format, and responses can be made vocally (by letter of the response choice) or by pointing to the answer choice. This format can be used with students who may have impairments in motor, speech, hearing, neurological and cognitive functions.It is untimed and takes about 25 minutes. Scoring is quick and uncomplicated. Raw scores are reported as scaled scores andpercentile ranksfor each subtest; the overall total score is reported as a standard score and percentile rank. Age-equivalents are also provided for the subtest and overall scores.

Specific test Scales for Unilateral Spatial NeglectAlbert's Test Unilateral spatial neglect (USN)Behavioral Inattention Test Unilateral spatial neglect (USN)Bells TestVisual neglect - extrapersonal spaceCatherine Bergego Scale (CBS)Visual neglect - extrapersonal spaceClock Drawing Test (CDT)Visuospatial and praxis abilities, may determine attention and executive dysfunctionsComb and Razor Test Unilateral spatial neglect (USN) - personal spaceDouble Letter Cancellation Test (DLCT) Unilateral spatial neglect (USN) in the near extrapersonal space

Draw-A-Man Test-Unilateral spatial neglect (USN) in the personal and extrapersonal space (as well as the presence of anosagnosia). Other constructs: intellectual ability/cognitive function/body imageLine Bisection Test-Unilateral spatial neglect (USN)Semi-Structured Scale for the Functional Evaluation of Hemi-Inattention-Unilateral spatial neglect (USN) - personal and extrapersonal spaceSingle Letter Cancellation Test (SLCT)-Unilateral spatial neglect (USN) - extrapersonal spaceStar Cancellation Test-Unilateral spatial neglect (USN) - extrapersonal space

The test sheet is presented to the patient at their midline. Some of the lines are pointed out to him/her, including those to the extreme right and extreme left. The examiner asks the patient to cross out all of the lines, and demonstrates what is required by crossing out the 5 central lines him/herself. The patient is encouraged to cross out all the lines until he/she is satisfied that they have all been crossed.ALBERTS TEST

Time to administer Less than 5 minutesEquipment:11x 8.5-inch page of paper with 41 lines 2 cm in length each and pencil.

Draw a man test evaluation

Using a blank piece of paper and a pencil, the seated patient must draw an entire man. The picture is scored by giving one point for the presence of each of the following body parts: head, trunk, right arm, left arm, right hand, left hand, right leg, left leg, right foot, and left foot. The total score of this version of the test is 10

Research Articles

Impact of Motor, Cognitive, and Perceptual Disorders onAbility to Perform Activities of Daily Living After Strokeby Louisette Mercier, MA et al . In (Stroke. 2001;32:2602-2608)Background and PurposeThis study evaluates the relative impact of motor, cognitive, and perceptual deficits on functional autonomy with 100 elderly (aged 55 to 79 years) victims of stroke.MethodsTwo different approaches were used for measuring functional autonomy: the Functional Autonomy Measurement System (Systme de Mesure de lAutonomie Fonctionnelle [SMAF]) and the Assessment of Motor and Process Skills (AMPS).

The Functional Autonomy Measurement System (Systme de Mesure de lAutonomie Fonctionnelle [SMAF]) is an instrument for evaluating autonomy that was developed on the basis of the theoretical framework of the World Health Organizations international classification of impairments, disabilities, and handicaps.It evaluates 29 functions covering activities of daily living (7 items), mobility (6 items), communication (3 items), mental functions (5items), and instrumental activities of daily living (8 items). Each function is scored on a 5-point scale (0, 0.5, 1, 2, and 3).The Assessment of Motor and Process Skills (AMPS) provides a measure of the quality of motor and process skills when the subject carries out an activity of daily living or a domestic activity.

Motor FactorEvaluated byUpper extremity functional hemiplegia (UEFH)Cognitive FactorMost of the various tests chosen to evaluate cognitive functions were taken from a neuropsychology battery called Protocole dvaluation Neuropsychologique Optimal (PENO).

Perceptual FactorEvaluation by MVPT-VThe Motor Free Visual Perception Test-Vertical (MVPT-V) evaluates visual discrimination, figure-ground differentiation, consistency of form, visual memory, and visual synthesis.Bells testA cancellation task using bells was developed by Gauthier et al and gives a more refined evaluation of the degree of unilateral visual neglect than previous cancellation tests).Benton testSpatial relation deficits were measured with the line orientation judgment test, which was considered by Beaumont and Davidoff to be a test of visuospatial functions.OSOT batteryThree subtests were taken from the Ontario Society of Occupational Therapy perceptual evaluation battery to measure visuoconstructional deficits/apraxia.Rey figure testVisuoconstructional deficits/apraxia were also measured with the complete detailed scoring system for the copy of Reys complex figure. Norms have been established for neurologically healthy people and for various groups of stroke patients.

Results:show that motor, cognitive, and perceptual factors all make a significant contribution to the variation in functional autonomy and confirm the accuracy of the model (93% of the variance is explained when the SMAF is used to measure functional autonomy, and 64% of the variance is explained when the AMPS is used).ConclusionsThe factors that make the greatest contribution in explaining the variance in functional autonomy are, in order of importance, the motor factor, the perceptual factor, and the cognitive factor.

Seeing The Gaps: A Systematic Review Of Visual Perception Tools For Children With Hemiplegia. MEGAN AULD, et al In 2011 disability and rehabilitation.Aim visual perception difficulties are common in children with cerebral palsy hemiplegia, however it is not known which assessment tool is the best for this population.Method: Databases were searched for assessments that: (i) measured visual perception; (ii) were reported in studies with children with hemiplegia and (iii) had clinimetric data available to assessors.

Results: Three assessments met criteria: the Test of Visual Perceptual Skills (TVPS), Motor-Free Visual Perceptual Test (MVPT) and Developmental Test of Visual Perception (DTVP). All three assessments demonstrate variable construct and criterion validity with other clinical assessments. The DTVP, MVPT and TVPS demonstrate high test-retest reliability for total scores, but individual TVPS subtests are less reliable.There is considerable overlap in content between the subtests of the examined assessments. There is, however, substantial variation in the manner in which these subtests are applied.The MVPT is a discriminative and evaluative assessment tool used in children aged 411 years. The MVPT displayed excellent inter-rater reliability.

Clinical utility- All three assessments have high clinical utility they are of a similar cost, do not require training to implement and are relatively easy to administer and score.Conclusions: The TVPS is the most rigorously investigated of the three assessments; however, this systematic review has uncovered significant flaws in both its validity and its reliability. The TVPS has some significant flaws in its test design, impacting both the validity and reliability of the test. At present the DTVP and MVPT demonstrate the strongest clinimetric properties and would, thus, be recommended for clinical practice.

Test-Retest Reliability of the Motor-FreeVisual PerceptionTest Revised (MVPT-R) in Children with and WithoutLearning DisabilitiesPatricia A et al in 2002, Vol. 22, No. 3-4 , Pages 23-36Aim and objective :The Motor-Free Visual Perceptual TestRevised(MVPT-R) is an updated edition of the original test with the addition of four items and normative data for 9-11-year-old children. Test-retestreliabilitystudies on the MVPT-R are not reported. The purpose of this paper is to report the test-retest reliability of the MVPT-R in children with and without learning disabilities. The MVPT-R was administered to 38 children with identified learning disabilities and 37 control children (aged 7-10 years) on two separate occasions within a 2.5 week window of time.Results suggest moderate test-retest reliability for the MVPT-R with more stability in visual perceptual scores for children with learning disabilities. This information will be helpful for therapists using the MVPT-R as a descriptive measure for children.

References Text book of physical rehabilitation sullivan.Pedretti 6th editionhttp://wiki.bethanycrane.com/introducingtheeyeUnsworth, C. A. (2007). Cognitive and Perceptual Dysfunction. In T. J. Schmitz & S. B. OSullivan (Eds.), Physical Rehabilitation (pp. 1149-1185). Philadelphia, F.A: Davis Company