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This outline was originally created by Chrissy Cowan and Carolyn Mason in the form of a powerpoint, which was updated by Jim Durkel and then by Sara Kitchen and Lynne McAlister.  You may also want to view the series of videotapes made by Sara Kitchen and Lynne McAlister related to CVI.

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Definition and Incidence

  • Definition of cortical visual impairment
  • New field of research
  • Fastest growing visual impairment
  • Diagnosis

The Problem with Medical Diagnosis

  • Eye report frequently doesn’t say “CVI”
  • Best information may come from neurological
  • Test like MRI is not necessarily useful in diagnosing CVI

Look for “red flags”

  • Asphyxia-damage depends on severity & duration.  Some causes:  placenta previa, prolapsed cord, delivery complications.
  • Hypoxic Ischemic Encephalopathy-too little oxygen (hypoxia), too little blood flow (ischemia), irritation of the brain (encephalopathy).  Results from asphyxia.  Seizures common.
  • Cerebral Vascular Accident-(stroke) blood capillaries in the brain rupture, damage depends on extent of bleed, more common in full term male infants, mostly affects left side of brain, seizures common.
  • Intraventricular Hemorrhage-occurs in premature infants w/in 1st 48 hours.  Severity grades I-IV.
  • Periventricular Leukomalacia (PVL)-something, such as trauma, occurs and oxygen does not get to the distant areas of brain.  These die and become filled w/ fluid (sometimes called cysts in the brain).  Can cause CP, developmental delays.
  • Infection-viral and bacterial (TORCH)=toxoplasmosis, rubella cytomegalovirus, herpes/HIV.  Also meningitis.

The Brain from Top to Bottom

brain - functional vision sections
Figure 1 Image of the brain including the functional subdivisions of the visual cortex, cerebellum, inferior temporal cortex (ITC), temporal lobe, lateral geniculate nucleus (LGN), frontal lobe, parietal lobe, and occipital lobe. (from  McGill University)

Current Trends in Neuroscience

  • Hardwired: Outdated theories stated that the brain was static and could not be healed once injured.
  • Neuroplasticity: Current beliefs include the brain’s ability to organize and reorganize itself.
  • http://www.youtube.com/watch?v=TCM4UBM8wTM)       

drawing by bhild with cvi
Figure 2. Drawing by an 8 –year-old child with CVI.  The eyes and hair are on the bottom of the drawing and the mouth is at the top.

Unique Characteristics of CVI

  • Color:  strong reaction/preferential response to a particular color, typically red or yellow.  Color receptors are diffused through brain & almost all children have some color vision.  Need their favorite color as a visual anchor.
  • Movement:  Stimulates the “aware” system, gets the visual system activated.  Movement w/out sound is generally easier to visually process.
    • Movement plus reflective qualities provide an invasive, difficult to ignore effect on the visual system.
    • Child may exhibit better than expected navigational skills.
  • Latency:  delayed response to presentation of object.  Can vary according to time of day, state of alertness, degree of stress, and neurological stability.  Decrease in latency equals increase in visual behavior.
  • Visual Field Preferences: objects are more easily seen in certain parts of the visual field.
    • Especially in periphery, where movement is better detected by the retina.
    • Mixed field preferences:  May use one eye for a field preference, and the other for verification.
  • Complexity:  most interfering of all characteristics. 
    • Target/object-some objects are too complex, and there is no place for child to anchor his vision and so vision shuts down: faces are very complex.
    • Array-what’s behind the object can cause problems even with preferred objects.  This is responsible for the misconception that vision is variable.  Actually, vision is constant, but background interferes with vision functioning.
    • Sensory environment-unable to process with more than one sense at a time; will defer to auditory over vision.   Be careful where you place auditory stimuli.  Limit talking while doing vision work.
  • Abnormal Reaction to Light-Photophobia/Light Gazing/Non-Purposeful Gaze-prominent in early stages.
  • Distance Viewing-As object gets farther away, complexity increases.  Makes child appear nearsighted.
  • Visual Reflexive Responses-absent, intermittent, or delayed blink reflex.  Blink to threat; blink when you touch the bridge of the nose.
  • Visual Novelty-strong response to familiar objects.  Appear to ignore novel items.
  • Visual Motor-look and touch may happen as separate events.

Resolution of Characteristics

  • Best chance for resolution is within first 3 years, but the possibility for resolution continues to exist into adulthood.
  • Characteristics will not resolve without structured intervention
  • Phase I:  Building visual behavior
  • Phase II:  Integrating vision with function
  • Phase III:  Resolution of all CVI characteristics

“For Children with CVI, it is important to determine where they are on the continuum of possible impact of CVI, to identify in this way what they are able to look at or are interested in looking at, and to give them as many opportunities to look as possible by integrating motivating activities and materials into their daily lives.  The goal is to facilitate looking.”  (Page 114, Roman-Lantzy, Cortical Visual Impairment: An Approach to Assessment and Intervention.)

Order of Resolution

  • Early resolution: light gazing, and visual reflexive response of blink to touch
  • Mid-Resolution:  color, latency, visual novelty, visual reflexive response of blink to threat, and movement
  • Later Resolution:  visual fields, visual motor, complexity, and distance vision

(http://www.aph.org/cvi/articles/bbf_1.html)

Introduction to Christine Roman-Lantzy’s Assessment

ORDER HERE: http://www.afb.org/store/product.asp?sku=978-0-89128-829-9&mscssid=5D71MSQKD5CF9PH5CBFVWJT0FU8LCPKC

Assessment Framework

  • Interview
  • Observation
  • Direct evaluation of student

Reliability

The Reliability of the CVI Range: A Functional Vision Assessment for Children with Cortical Visual Impairment, by Sandra Newcomb, Journal of Visual Impairment & Blindness, October 2010, © 2010 AFB.

Parent Interview/Teacher Interview

  • Information on medical background
  • Eye report
  • What does child like to look at
  • What are your concerns
  • Child’s favorite color
  • When is child most visually alert
  • Does child look directly into faces
  • Does child notice things that move more than things that are stable
  • Does child seem to look “through” rather than at objects

Observation of Vision

  • In living and learning environments
  • Quiet and noisy times
  • Near and distance
  • Familiar and unfamiliar objects
  • Cluttered and simple backgrounds
  • Interest in objects of specific color (color preference)
  • Movement
  • Light gazing
  • Preferential viewing

Direct Evaluation

  • Evaluate range of visual functioning
  • Evaluate presence and degree of individual CVI characteristics
  • May need several sessions to test 

Forms

  • Parent Interview questions are on page 34 of book.
  • Answer Guide to Parent Interview – the page after page 40, appendix 4a.
  • Rating 1– Across CVI Characteristics Method – Figure 5.2, the page after page 56
  • Rating 1 – CVI Scoring Guide – page after page 96, appendix 5a.
  • Rating 2 – Within CVI Characteristic Method/CVI Resolution Chart – Figure 5.6, the page after page 74. 
  • Essential Forms are also at the end of the book, the page after page 185