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CVI – Background and Assessment Part 1
Heather Brooks, Educational Consultant
North Carolina Department of Public Instruction
VisionEye Brain Processing MovementExample: You’re walking along in the park and you see these three bears.
Quick Review of the Eye:I know you know this
Video: How the Eye Works and the Retinahttps://www.youtube.com/watch?
v=Sqr6LKIR2b8
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.
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 oxygenand 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
THE MOST COMMON CAUSEOF CVI IS HYPOXIC-ISCHEMIC
INJURY.
Examples: Brain Damage
Shunt FailureInfectionsMetabolic DiseaseDrugsMicrobesStrokeTraumaComplications 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 childrenNeurological 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.*
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.
Profound Functional Blindness
Idiosyncratic Impact on Vision
Mild Severe
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 CVILeading 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 ImpairmentCerebral Visual ImpairmentNeurological Visual ImpairmentDelayed Visual MaturationCortical BlindnessCortical 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
Dutton Theory ContinuedDorsal Stream
Vision-for-ActionDysfunction 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 StreamVision-for-Perception
Dysfunction in this area:• Prosopagnosia• Difficulty understanding
facial expressions• Route finding problems• Various visual agnosias
(inability to visually identify objects)
Lea Hyvärinen, MDFinnish 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 Totshttps://www.youtube.com/watch?
v=3JcAsXuy7ac
Christine Roman-Lantzy, Ph.D
1. Color Preference2. Need for movement3. Visual latency4. Visual Field preferences5. Decreased visual complexity6. Light-gazing & non-purposeful gaze7. Decreased distance vision8. Atypical visual reflexes9. Decreased visual novelty10. Decreased visually guided reach