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 Severe Idiosyncratic Impact on Vision 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

Vision for Action Vision-for Perception

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

1.

Test Your Facial Recognition Skills

Lighten things up

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.