Vision and the MultiImpaired

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Vision and the Multi-Impaired

• Visual Acuity
• The Process of Seeing
• Eligibility for Visiting Teacher Support
• Cortical Visual Impairment

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The Process of Seeing

• Vision is a perceptual process with three basic
  parts
• the eye
• the optic pathways
• the brain
• For vision to occur all three of these processes
  must be functioning

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Vision and Vision Acuity

• Measure Vision two ways

Clinical Measurement Functional Measurement
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Clinical Measurements

• Two Types of Acuity
• Near Acuity-measured in N point readings
• Distance Acuity-measured in Snellen Fraction
• Fields assessments measured in degrees

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Visual Acuity

• Visual acuity is the ability to see detail at
  distance
• Near and far.
• A persons visual acuity is recorded as a
  Snellen
• Fraction. The numerator represents the testing
• distance. While the denominator indicates the
• smallest letter size the person can see.

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Functional Acuity

• Functional Acuity refers to what the child can
  see
• and in what circumstances. Often more helpful
  than
• Clinical measurements.
• Components of Functional Assessment include
• muscle balance-do eyes work together
• visual fields
• fixation
• avoidance
• eye movement-tracking and scanning
• Determine Functional Acuity Record
• size
• shape
• colour

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Cortical Visual Impairment
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Multi-impaired Children.

• This population includes children with
• Ocular damage
• Global damage
• Cortical visual damage
• Each of these require different management
  strategies.

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Definition of Cortical Visual Impairment

• CVI is reduced vision that is associated with
  normal or miminal ocular abnormalities, lesions
  involving the visual cortex, widespread
  neurological disease and frequently visual field
  and visual perception abnormalities

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Global Damage Verses Cortical V.I

• True CVI occurs in the areas 17,18,19 of the
  ocipital cortex. These are the areas specific to
  vision.
• Many children called CVI have global damage.
• Natalie Barraga believes that a childs visual
  skills can never be greater than his/her overall
  mental ability.

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Causes of CVI

• Anoxia, hypoxia, ischaemia, asphyxia
• Lack or insufficiency of oxygen.Visual
  cortex can only survive approx. 4 minutes without
  oxygen.
• Cerebral haemorrhage/cortical thrombrosis
• Dysgenesis-malforamation of the brain during
  prenatal development.
• Trauma-car accidents, shaken baby syndrome.
• Near-miss Sudden Infant Death Syndrome.
• Severe central nervous system infections-meningiti
  s, encephalities
• Shunt Malfunction in children with hydrocephalus.
  

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Characteristic Features of CVI
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• Appearance

• Doesnt look blind
• Expressionless face
• Eye movement smooth,slow but aimless
• Visual self-stimulation is rare
• Visually inattentive
• Tends to look away from people and events
• Disminished visual communication
• Normally reacting pupils
• Blink reflexes e.g blink to a threat
• No optical/sensory nystagmus is present
• Additional neurological impairment always present

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Visual Functioning

• Visual abilities fluctuates
• Peripheral vision appears to be more functional
• Attends to moving objects-children tend to see
  better when travelling in a car
• Sees better in familiar environment
• Lacks visual curiosity/inattention
• Spontaneouly use vision for short periods of time
  only
• Tires easily during visual learning

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Visual Functioning

• Jerks head from side to side when looking
• Turns head when reaching
• Visual field restrictions apparent
• Some children respond selectively to visual
  stimuli
• Colour can be important to some children
• Some children engage in light gazing
• Some are light sensitive (1in 4 are photophobic)

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Visual Perceptual Abilities

• Appears unable to recognise stationary objects
• May not recognize faces
• Needs wide spaces between objects and visual
  stimuli
• Focuses on only one toy among several
• Reach inaccurate
• Identifies colour more easily than objects or
  shape
• Familiarity of environment or objects can aid
  recognition
• Little generalizations
• Difficulty seeing objects or pictures placed
  close together crowding effect

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Sensory Modalities

• Supplements vision with touch
• Uses hand searching movements when location
  objects
• Appears to hear better when eyes are shut
• Child appears to see better when travelling in a
  car
• Many children with CVI are not capable of
  filtering our sensory information

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Posture and Movement

• Rarely bumps into objects during travel
• Balance seems better when eyes are closed
• Usually holds head up except when reaching

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Assessment

• Ophthalmological Assessment
• History
• Vision
• following movement of eyes and head
• fixation of a light
• optokinetic nystagmus
• response to a threatening gesture
• blink reaction to a bright light.

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Assessment

• Ocular Movements
• Range of movements
• Nystagmus
• Responses to body rotation
• Responses to non visual sensory stimuli
• Sound
• Touch
• Pain
• The purpose of electrical tests is to determine
  the extent and location of brain damage.
• Ophthalmoscopy

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Electrical Testing

• Various Testing Available
• Electroretinaogram (ERG)
• Electooculogram (EOG)
• Visual Evoked Response (VER)
• Visual Evoked Potential (VEPM)
• Electroencephalogram (EEG)
• Computer Tomography (CT scan)
• Magnetic Resonance Imaging (MRI)
• Position Emission Tomograhpy (PET)

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Functional Vision Assessment

• Visual Acuity
• responses to light
• responses to threat
• responses to objects making note of size
  and colour
• response to colours using brightly
  coloured cards of A3 to A4 size
• fixation needs to described in terms of
  length and pattern

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Functional Vision Assessment

• response to patterns
• chequerboard
• zig zag
• stripes black and white and then add red
• Response to people and stylised faces
• If children are more able, an acuity measurement
  can be attempted through use of
• Teller Acuity Cards
• Stycar balls
• Catford Drum

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Functional Vision Assessment

• Subjective Measurements can be attempted through
  the use of
• Sheridan Gardiner
• Picture Tests- Pigassou, Kays
• Stycar Toys.

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Management of Cortical Visual Impairment

• Natalie Barraga believes that a childs visual
  skills can never be greater than his/her overall
  mental ability.
• A sufficient level of general awareness of the
  child is critical before starting an intervention
  program.

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Management of Cortical Visual Impairment

• Environmental Considerations
• Sensory filteringcreate a quiet,
  stimuli-restricted environment.
• Control the
• Type
• Intensity
• Duration of sensory input

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Management of Cortical Visual Impairment

• Well lit area for working, indirect light source
• Work in familiar area or setting
• Provide optimum positioning of the child-head
  upright and in midline
• Position of Stimulus
• Distance up to 3 months child sees no further
  than approx.75 cm from himself, bigger objects
  150cm
• Field offer stimluli in every part of normal
  field, determine best area, then expand field of
  visual attention
• Background simple stimuli against neutral but
  contrasting

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Management of Cortical Visual Impairment

• Visual skills
• Awareness
• Fixating
• Shifting gaze
• Tracking horizontal, vertically , obilquely,
  all around
• Accommodation / Convergence
• Scanning

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Management of Cortical Vision Impairment

• Perceptual Skills
• Visual Discrimination
• recognition
• matching
• consistency
• Figure Ground
• distinguishes dominant features
• tracks
• organizing the visual fields

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Management of Cortical Vision Impairment

• Visual Memory
• Intention
• Imiation
• Sequencing
• Retention
• Visual Closure
• Parts to whole
• Identify distinctive features

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Management of Cortical Vision Impairment

• Spatial Relations
• Visual motor
• Position of self in space

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Management of Cortical Visual Impairment

• Key considerations are
• Simplicity
• Familarity
• Timing
• Color vision use yellow, red, orange
• Verbal and tactile cueing
• Use familiar/real objects.
• Visual responses may need confirmation from
  tactile sense.

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Management of Cortical Visual Impairment

• Use moving objects, this may enhance visual
  performance
• Minimize crowding
• Adopting a shortened focal length-hold stimuli
  close to child.
• Use title board to place work close and cut out
  backgroud information
• Widely separate objects/pictures
• Point to objects, pictures, words etc.

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Management of Cortical Visual Impairment

• Short periods of structured activities, frequent
  rest breaks may be required
• Control type, instensity and duration of sensory
  imput
• Repetition is helpful, use same object
• Present objects in dominant field
• Allow time to to obtain a response

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Management Comparisons

• Occular damage and global damage we try to
  maximize the childrens visual imput ie. visual
  stimulation.
• Cortical damaged we try to reduce and organize
  the environment to minimize visual stimuli.

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Useful References

• Paediatric Data Base
• www.icondata.com/health/pedbase/indexhtm
• See Hear
• www.tsbvi.edu
• California Deaf Blind Services
• www.sfsu.edu/cadbs/