CVI – Background and Assessment Part 1

Heather Brooks, Educational Consultant

North Carolina Department of Public Instruction

Today we’ll be discussing

Today we’ll bediscussing....Brains & Eye Balls

VisionEye Brain Processing MovementExample: 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 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.

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 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.*

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.

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

Visual stimulus is processed in lots of places in the brain

Vision-for-Action

Vision-for-Perception

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)

Visual Agnosia

Video: My Strange Brain https://www.youtube.com/watch?

v=kuKqi93FMgQ

Lighten things up Test Your Facial Recognition Skills

1. 2.

3. 4.

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

Part 1 APH “CVI Perspectives”

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

Homework

Identify 3 online or hard copy articles pertaining to CVI.

Write a summary of the findings for one of the articles.