5/30/2013

Cortical Visual Impairment - Discovering the world through the eyes of CVI



  

What is CVI?


  According to Dr. Roman-Lantzy, Cortical Visual Impairment (CVI) “is the leading cause of visual impairment in children today”. CVI differs from other types of visual impairment which are due to physical problems with the eyes. CVI is a neurological disorder caused by damage to the visual centers of the brain, which interferes with communication between the brain and the eyes. The eyes are able to see, but the brain is not interpreting what is being seen.

     When a child exhibits one or more visual or behavioral characteristics indicating impairment in his/her visual and/or visual perceptual abilities, a neurologist, ophthalmologist, or other medical specialist may diagnose the child with CVI. The level of severity can range from mild to severe depending on the age of individual at time of insult along with the location and intensity of the damage.    

     CVI is the inability of the brain’s visual systems to consistently process and interpret visual information. CVI is not a disease or a condition of the eye itself or an indicator of cognitive skills. CVI is also known as neurological visual impairment, cerebral visual impairment, delayed visual maturation, or cortical blindness. In North America the condition is described as “cortical visual impairment.” In Europe, the term “cerebral visual impairment" is used.
Causes of CVI:
     There are many conditions that can cause CVI, including anoxic brain damage, periventricular leukomalacia (PVL), hypoxic (reduced oxygen to tissue) brain damage found in babies who experience SIDS, but live, individuals who experience a cardiac arrest, individuals resuscitates from drowning, individuals who have experienced extended episodes of epileptic seizures. Other causes include meningitis, encephalitis, head injury, intraventricular hemorrhage, structural brain developmental disorders (such as hydrocephalus, spina bifida, agenesis of the corpus callosum, and microcephaly) and metabolic conditions. Approximately 80% of children with cerebral palsy also have CVI. 

     As more critically ill babies are surviving the incidence of CVI is increasing. This makes it even more important that people know about and understand CVI.
General Characteristics of Individuals with CVI:
  • Normal or minimally abnormal eye exam (CVI may co-exist with optic nerve atrophy, hypoplasia or dysplasia and ROP.)
  • Difficulty with visual novelty (The individual prefers to look at old objects, not new, and lacks visual curiosity.)
  • Visually attends in near space only
  • Difficulties with visual complexity/crowding (Individual performs best when one sensory input is presented at a time, when the surrounding environment lacks clutter, and the object being presented is simple.)
  • Non-purposeful gaze/light gazing behaviors
  • Distinct color preference (Preferences are predominantly red and yellow, but could be any color.)
  • Visual field deficits (It is not so much the severity of the field loss, but where the field loss is located.)Visual latency (The individual's visual responses are slow, often delayed.
  • Attraction to movement, especially rapid movements.
  • Absent or atypical visual reflexive responses (The individual fails to blink at threatening motions.)
  • Atypical visual motor behaviors (Look and touch occur as separate functions, e.g., child looks, turns head away from item, then reaches for it.)
  • Inefficient, highly variable visual sense
  • May also have visual impairments such as optic nerve atrophy, optic nerve dysplasia, strabismus. 
  • Often have no or a poor visual response even in the presence of a normal vision exam and normally functioning pupils. 
  • May have multiple disabilities to include motor and/or cognitive delays, problems communicating and learning language as the result of cerebral palsy, seizures, severe to mild learning disabilities and other neurological problems.
Diagnostic Signs of CVI:  
  • The lack of blinking (atypical visual reflexes).     
  • Staring at lights for an extended period. (light gazing preference).     
  • Tends to turn his or her head to the side when reaching for an object (unable to demonstrate an intact visual guided reach).      
  • A short visual attention span, but may improve if object is moving.     
  • Problems with looking at an object presented at a distance (distance viewing is difficult and   varies at different phases).      
  • Fluctuations in visual functioning throughout the day.     
  • Perceives color—has color preference of usually red or yellow.     
  • Problems with objects presented in some visual fields (visual field preferences may use one peripheral field better or may use central vision).     
  • Fatigues quickly when engaged in visual activities.     
  • Items in parenthesis are key visual behaviors to assess and target in treatment.     
  • Prefers to look at familiar rather than new objects (problems with visual novelty).     
  • Needs extended response time when looking at objects.      
  • Problems looking at objects that are visually complex (difficulties with visual complexity). 
Scoring range for CVI:

Phase I: CVI Range Level 0 to 3 (inconsistent visual attention on objects)
- Need single color or personally preferred color  
 objects.
- Shiny objects.
- Objects with movement .
- Familiar objects.
- Objects presented in a simple background.
- Identify 3-5 objects to use with an individual based on observation and assessment.
- Suggested objects: slinky, reflective pinwheel, windsock, Elmo doll, mobile made out of    silverware.
-  Design activities focusing on the use of these objects for repeated practice in a supportive environment.

If individual demonstrates signs of fatigue (such as yawning, avoiding looking, sleeping, closing eyes, grimacing, yawning, etc.) try:
   - Reducing stimuli.
   - Providing longer periods of visual gazing.
   - Reducing stimuli in setting.

Phase II: CVI Range Level 4 to 7 ( some functional use of vision )
   Use individual’s favorite color and add one or two more colors.
       - Individual should begin to tolerate more complex visual patterns.
   Put reflective strips on objects.
       - Reduction in light gazing by individual
   Use objects from daily routines and activities that are the individual’s preferred color    
   - May also wrap in reflective material.
   - Includes toothbrush, cup, fork, switches,lightbox, etc.
   - Use new objects that are the individual’s preferred color during activities.
   - Place objects on black or plain backgrounds to support the visually guided reach skill.

Phase III: CVI Range Level 7 ½ to 10 ( using vision to perform most activities )
     - Beginning to demonstrate a visually guided reach.
     - Problems continue with complex visual setting.
     - Difficulty with images/words on paper.
     - Problems with objects over 10-15 feet from the individual.
   
Suggested objects: highlighters, simple picture books with outline only, theme based books “my favorite toys”, “foods I like to eat” and others, use photos only of faces initially, can begin to use mirrors, communication symbols of individual’s favorite color, and favorite items with simple backgrounds.
   
Focus on two major skills in this phase:
1) Activities should be designed to support the individual in improving skill in determining how    objects are the same or different using visual features.
   - For example, taking old information or familiar object and relate it to something new but similar as the actual interaction takes place with the new object. (i.e. compare a bus to the family car) 
2) Support the individual to use his or her vision to discern visual details from the background,   visually discriminate within the setting and deal with visually complex objects successfully.
For example:
     Begin with a simple book that uses the individuals favorite color for the main character or object in the story, such as Clifford, the red dog. The activities range from finding a stuffed Clifford, to using a pop-up book about Clifford to visually locating a Clifford dog with movement to finding smaller Cliffords in a “hidden picture” type activity.
Three Important Educational Beliefs:
  1. Children with CVI have the capacity to see more effectively and become more active and fulfilled participants in their school environment.
  2. Improved vision and school participation is dependent on a carefully designed educational program consisting of enjoyable and simplified activities embedded in familiar routines and specific to each child’s unique visual and learning needs.
  3. Effective learning requires that well-trained team members work collaboratively in order to improve vision and learning for children with CVI.
    (Adapted from Edelman, et al., 2006)

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1 comment:

  1. Nice overview of CVI.
    -Olivia's mom, oliviacansmile.blogspot.com
    Facebook page: https://www.facebook.com/cvicommunity?ref=tn_tnmn

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