CVI – Background and Assessment - No Videos

Report
CVI – Background and
Assessment Part 1
Heather Brooks,
Educational Consultant
North Carolina Department of Public
Instruction
Today we’ll be
discussing....
Brains & Eye Balls
Vision
Eye
Brain
Processing
Movement
Example: You’re walking along in the park
and you see these three bears.
Brain Thinking About Grizzly Bears
Motor Action Taken After Seeing a
Grizzly
Quick Review of the Eye:
I know you know this
Video: How the Eye Works and the Retina
https://www.youtube.com/watch?v=Sqr6LKIR2b
8
Brain Structure
Vision is not simply processed in the visual cortex.
There are numerous places in the brain responsible
for interpretation and reaction to visual stimulus.
Cortical Visual Impairment
• CVI occurs due to damage in the brain.
• So let’s talk about brain damage for a minute.
What’s the Cortex?
Cerebral Cortex
Cerebrum
Brain Damage
The human brain…
Has a limited ability to store glucose or oxygen.
It is also encompassed in a hard shell (skull) that
doesn’t allow for much swelling.
Brain Damage –
Oxygen, Glucose, & Waste Management
Blood brings with it fresh oxygen
and glucose.
Blood takes away the waste that
builds up in the cells.
Without fresh,
oxygen rich
blood….
cell death occurs.
Brain Damage –
2 Important Terms
• Ischemia – lack of blood supply
• Hypoxia – lack of oxygen
Examples: Brain Damage
Shunt Failure
Infections
Metabolic Disease
Drugs
Microbes
Stroke
Trauma
Complications of Cardiac treatment…
Neuralplasticity:
Finding a New Path
• The brain can learn to reroute information/find new neural
pathways
• Visual recovery is better for younger children
Neurological Insult in Children
• Neurological improvement happens for two or more years
after the injury
• Children recover better in the immediate time frame and
improve for longer periods
*Important that we not set limits or have a predetermined idea
of what a child can learn or how far a child can progress.*
Just to lighten it up for a moment.
What is CVI?
• Cortical Visual Impairment
• No single definition for CVI
• Generally speaking, CVI is vision loss due to
damage in the brain
• CVI can manifest in different ways, with a wide
range of severity.
Mild
Idiosyncratic
Impact on Vision
Severe
Profound Functional
Blindness
How is CVI diagnosed?
• Clinical diagnosis – no specific medical test for
CVI
• Normal eye exam – or the eye disorder does
not explain the visual behavior
• History of neurological insult
• Demonstrate unique visual and behavior
characteristics associated
with CVI
Examples of Unique Visual and
Behavior Characteristics
• Slow, inefficient, and highly variable visual
performance
• Light gazing/Photophobia paradox
• Color vision and perception of movement is
often preserved
• Look
Look Away
Reach
• Visual Agnosias (inability to recognize)
Prevalence of CVI
Leading cause of pediatric visual impairment in
the developed world. Because…
Improved
survival
Other
blindness have
decreased
Comorbid Conditions
•
•
•
•
•
•
•
•
•
Epilepsy
Cerebral palsy
Intellectual disabilities
Hearing loss
Hydrocephalus
Abnormal mental development
Microcephaly
Progressive degenerative disorders
Hypotonia
Lots of Names with Visual
Impairment Involving the Brain
Cortical Visual Impairment
Cerebral Visual Impairment
Neurological Visual Impairment
Delayed Visual Maturation
Cortical Blindness
Cortical Visual Dysfunction
CVI Perspectives
• Gordon Dutton – Medical
• Lea Hyvärinen – Medical
with strong emphasis on optics
• Roman-Lantzy – Educational
Gordon Dutton, MD
• Lower Level CVI
– Damage to the visual pathway at the striate
cortex
– Results in damage to visual acuity, understanding of
what is being seen, and visual fields may be impacted
• Higher Level CVI
– Damage occurring beyond the striate cortex
– Specific functional loss of vision (e.g., movement,
shape, or color)
• Both
Visual stimulus is processed in lots of
places in the brain
VisionforAction
Vision-forPerception
Dutton Theory Continued
Dorsal Stream
Vision-for-Action
Dysfunction in this area:
• Difficulty complex visual
scenes
• Issues moving through space
• Trouble finding an
object/person from within a
group
• Inaccurate visual reaching
• Decreased lower field
• Frustration
Ventral Stream
Vision-for-Perception
Dysfunction in this area:
• Prosopagnosia
• Difficulty understanding
facial expressions
• Route finding problems
• Various visual agnosias
(inability to visually identify
objects)
Visual Agnosia
Video: My Strange Brain
https://www.youtube.com/watch?v=kuKqi93FM
gQ
Test Your Facial Recognition Skills
Lighten things up
1.
2.
3.
4.
Lea Hyvärinen, MD
Finnish Pediatric Ophthalmologist
• Dorsal, Ventral, and…. Mirror Neurons
– Mirror neurons are activated when
watching others
– Important in visual communication
– Foundation for imitation of expressions and
thus emotional bonding
Additional Medical Views of CVI:
Lea Hyvärinen, MD
• Scotoma:
Blind spot in
the visual field
• Scotomas and CVI:
– Central scotomas “very common in children with
CVI”
– If the child is looking away to look at something,
eccentric fixation may be what they’re using
Additional Medical Views of CVI:
Lea Hyvärinen, MD
• Saccade: fast movements of the eye that are
present in normal visual functioning and
important in visual tasks like reading
• Saccade and CVI:
– slower than normal
– inexact in landing at target
– or there may be no fast eye movements at
all
Lea Symbols:
Lea Hyvärinen, MD
Optotypes - symbols used to determine visual
acuity for prereaders or students with other
disabilities
Lea Hyvärinen Cont.
Video: Baby Eyes: A Vision Test for Tots
https://www.youtube.com/watch?v=3JcAsXuy7a
c
Christine Roman-Lantzy, Ph.D
Part 1 APH “CVI Perspectives”
Christine Roman-Lantzy, Ph.D
1. Color Preference
2. Need for movement
3. Visual latency
4. Visual Field preferences
5. Decreased visual complexity
6. Light-gazing & non-purposeful gaze
7. Decreased distance vision
8. Atypical visual reflexes
9. Decreased visual novelty
10. Decreased visually guided reach
Homework
Identify 3 online or hard copy articles pertaining
to CVI.
Write a summary of the findings for one of the
articles.

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