Visual Impairments

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Visual Impairments

• Deaf/Blind Special Considerations

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Structure of the Eye
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Vision and Motor Performance

• Acuity-
• Static Visual Acuity-
• Dynamic Visual Acuity-

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Dynamic Visual Acuity

• Reflects the ability of the muscles of the eyes
  (ocularmotor system) to catch and hold an
  objects image on the eyes fovea
• Improves between 6 and 20 years
• Decreases as speed increases

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Static Visual Acuity

• Snellen eye chart
• Improvement occurs over the first 4 to 5 years of
  life
• Birth (20/300 - 20/800)
• Year 1 (20/100 - 20/200)
• Rapid 5 to 7 (20/40)
• Rapid 9 to 10 (20/20)

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Vision Tests - Infants

• Fixing and following
• Opticokinetic response
• Preferential looking test
• Visual evoked responses (VERs)

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Vision and Motor Development - Infants

• Developmental delays
• Muscle tone depends partly on visual perception
• visual curiosity elicits movement
• Ex. motor milestones
• How to avoid developmental delays?
• Use various other sensory modalities to elicit
  movement, exploration, and play

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Visual Acuity and Motor Performance - Children

• Motor skill performance
• Exercise
• Age

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Field of Vision

• Peripheral Vision
• 180 lateral
• 112 vertical
• Adults greater than children
• Key to many movement endeavors

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Eye Dominance

• Ability of one eye to lead the other in tasks
  involving visual tracking and visual fixation
• Eye Dominance Test

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Tracking and Object Interception

• Tracking-
• Horizontal plane-
• Arc-
• Ocular motor system and motor system work
  together to track and act

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Coincidence-Anticipation Timing

• Improves with age
• Greatly influenced by practice
• Greater chances for error in very slow or very
  fast moving objects
• Implications

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Visual Impairments

• Legal Blindness/Visual Impairment Definition
• Each state has its own definition
• Blindness Less than 20/200 vision with best
  correction, or
• Less than 20 degree visual field with best
  correction
• Incidence - 1 in 3,000
• 25 total blindness
• 25 partial blindness
• 50 can read enlarged type
• Visual Impairment
• Visual impairment that, even with correction,
  adversely affects a childs educational
  performance
• Incidence
• 0.1 of school population or appx. 100,000
  students (10k deaf/blind)
• 55 males / 45 females

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Blindness

• Causes
• Heredity (37)
• Anoxia
• Intrauterine infections
• Head trauma
• Retinoblastoma
• Nutrition disorders (vitamin A deficiency)
• Two types
• Cortical - problem along visual pathway
• Retinal - eye structure itself

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Function and Diseases of the Eye

• Cornea
• Myopia
• Hyperopia
• Astigmatism
• Lens
• Cataract
• Presbyopia
• Anterior Chamber
• Glaucoma

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Function and Diseases of the Eye

• Eyeball muscles six muscles
• 1-2. Lateral / medial rectus (left/right)
• 3-4. Superior / inferior rectus (up/down)
• 5-6. Superior / inferior oblique (rotate)
• Loss of coordinated movement leads to strabismus
  abnormal alignment of the eyes
• Esotropia (cross-eyed) most common
• Exotropia (wall-eyed) eyes turn out

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Identification Nine Warning Signs

• Clumsiness
• Holding materials close to the eyes to see it
• Lack of attention
• Constant need for explanation of what is
  happening at events
• Extreme sensitivity
• Extreme squinting
• Excessive eye rubbing
• Poking the eyes with fingers or knuckles
• Physical anomalies such as swollen eyes or
  strabismus

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Instructional Strategies

• Eliminate clutter
• Braille labels on items in classroom
• Allow computer to produce work
• Learn some Braille
• Have another student read assignments from books
  not available in Braille or on tape
• Recognize that some vocabulary words mean nothing
  to a person who has never seen them
• Use large print with contrasts (if residual
  vision)

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Deaf/Blind Considerations

• Separate category in 1969
• When maternal rubella was causing a significant
  increase in the number of babies born with
  sensory deficits
• Low incidence category
• Defined
• Visual acuity of 20/200 or worse with best
  correction, has a chronic hearing impairment so
  severe that most speech cannot be understood, and
  for whom the combination of impairmentscauses
  extreme difficulty in daily life activities

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Assistance at most basic level

• Must maintain focus to realize
• They exist
• Others exist
• They have needs
• These needs can be met
• They can meet some of their needs
• Some, if not most, of their needs will be met by
  others
• Attention begins with touch
• Incidental Learning
• Learning must be direct
• Use residual hearing/vision and technology to
  assist