Transcript CVI - Part 6 - Teaching Students who are Blind or Visually Impaired

Session : Wednesday, October 13, 2015:
CVI
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Housekeeping
◦ Discussion
◦ Quiz
◦ CVI Assignment/CVI Quiz
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CVI
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Overview
Causes of CVI
Ophthalmological exam
CVI Characteristics
CVI Assessment
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CVI: Cortical Visual Impairment or Cerebral
Visual Impairment
Interference in visual function exists in the
visual processing centers and visual pathways
in the brain
Describes a condition when an individual is
visually unresponsive, but has a normal eye
exam
◦ May have abnormal MRI or CAT scan showing
damage to the areas of the brain containing the
visual pathway
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The term cortical blindness was first used in
the early 20th century to describe the
temporary or permanent loss of vision in
adults who experienced
◦ Hypoxia
◦ Circulatory or inflammatory disease
◦ Traumatic injury
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This term is not appropriate in describing the
visual dysfunction in children who have
damage to the visual centers of the brain
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The ability of cortical cells to interpret
messages sent from the retina develops in
infancy
◦ Even short lapses in light and pattern exposure can
permanently impair vision
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Development of vision is dependent on:
◦ An intact ocular system
◦ Exposure to stimuli
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Specific visual functions are dependent on
corresponding experiences
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There are various opinions about the specific
time frame surrounding the brains period of
plasticity
◦ There is agreement that visual development occurs
early in life and that there is a finite amount of time
to expose children to appropriate visual inputs
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Even children with a serious brain injury at a
young age, may be able to benefit from this
critical period
◦ Rerouting neurons from damaged areas to healthy
areas of the brain responsible for visual functions
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A delay in identifying children with CVI
prevents us from taking advantage of the
critical period
Children with CVI require:
◦ Prompt identification
◦ Careful assessment
◦ Planned interventions
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CVI is the most common cause of visual
impairment in children in the US
Most common in children:
◦ Born prematurely
◦ With neurological disorders
◦ With acquired brain injury
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Asphyxia and Perinatal Hypoxic-Ischemic
Encephalopathy
◦ When the brain is deprived of oxygen and glucose,
there is a chance of long-term brain dysfunction
◦ Damage depends on the severity and duration of
the episode
 If severe, cell death is the result
 Can cause organ damage, CP, Seizures, hearing loss,
CVI
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Intraventricular Hemorrhage
◦ Bleeding that occurs in the germinal matrix,
ventricles and surrounding tissues of the brain
 Premature infants are at a higher risk of this
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Periventricular Leukomalacia
◦ Injury to or death of the white matter of the brain
◦ Occurs when low blood flow injures the vulnerable
cerebral white matter of the brain in premature
infants (prior to 32 weeks gestation)
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Cerebral Vascular Accident/Cerebral Artery
Infarction
◦ Stroke
◦ Occurs when blood capillaries in the brain are
ruptured
 Obstruction
 Abnormal increase in blood pressure
 Problems with clotting
◦ Usually seen in full-term infants, but occasionally in
premies
◦ Infants are more likely to have seizures (esp. in the
first few days of life), CP, Dev. Delay and CVI
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Infection
◦ Infections can be passed from mother to fetus in
utero and can cause damage to the brain
 Toxoplasmosis
 Rubella
 Herpes simples
◦ Bacterial infections (Strep B, E. coli) can cause
sepsis and meningitis in infants
 Meningitis can cause hearing deficits, CP and CVI
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Structural Abnormalities
◦ Alterations in the normal progression of the brain
development may result in structural abnormalities
that can cause developmental and neurological
consequences
◦ Chromosomal abnormalities, infections, or
idiopathic incidents can cause:
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Meningomyelocele (Spina Bifida)
Dandy Walker Syndrome (cyst in brain)
Primary Microcephaly (small brain)
Hydrocephalus
Agenesis of the corpus callosum (no connections
between hemispheres of the brain)
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Metabolic Conditions
◦ Condition that may cause significant neuronal damage
 Severe Hypoglycemia (low blood sugar)
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Acquired Causes
◦ Traumatic injury to the brain in the perinatal period can
cause CVI
 Acquired apoxia (near-drowning, near-SIDS
Blows or gunshot wounds to the head
 Head injuries from auto accidents
 Shaken baby syndrome
 Tumors
 Optic radiation damage
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Normal eyes!!!
May show abnormality of the optic nerve
◦ Not enough to explain the visual impairment
Strabismus
Not usually nystagmus
Normal pupil reactions
Light gazing OR photophobia
Avoidant social gaze
Brief fixation
Intermittent tracking
Poor visual acuity
Visual field loss
“It is estimated that over 40 percent of the
brain is devoted to visual function, so it is not
surprising that a large proportion of children
with damage to the brain have visual
problems” (Christine Roman)
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Proceedings of the Summit on Cerebral/Cortical Visual
Impairment: Educational, Family, and Medical
Perspectives, April 30, 2005 (APH)
https://www.emeraldeducationsystems.com/
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Christine RomanLantzy
Dr. Gordon Dutton
Lea Hyvarinen
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Inability of the brain to recognize visual
stimulus even though the eye sees it.
May not recognize common objects until they
are held, but is aware they are there and can
reach for them.
Oliver Sacks
Facial agnosia
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CVI range/scale
CVI characteristics
Resolved characteristics
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A Normal eye exam or the existence of a
visual impairment that does not explain the
functional visual behaviours.
Unique visual behaviours related to CVI.
Existence of other neurological disabilities,
prematurity.
CVI can improve or worsen depending on the
environment and/or health of child.
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Distinct colour preferences
Attraction to movement
Visual latency
Visual field preference
Difficulties with visual environmental
complexity
Light-gazing
Difficulties with distance viewing
Absent or atypical visual reflex responses
Difficulties with visual novelty
Absence of visually guided reach
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Traditional FVA methods are not useful for
most students with CVI.
CVI range
Often CVI range with FVA.
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According to a study from the Pediatric VIEW
Program of Western Pennsylvania Hospital :
55% red, 34% yellow, 11% other or no colour.
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There is disagreement that it is a true colour
preference or related to something else:
brightness of object, contrast/surroundings,
familiarity, etc.
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Although it is unclear as to the reason for the
colour preference, it is an important factor to
consider when working with a child with CVI.
“Use of the preferred colour can serve as a
sort of visual “anchor,” a way to attract
attention toward specific objects or symbols”
(Roman, 2010, p. 22)
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Using the preferred colour to write the ABC’s
Or use highlighters to highlight or
underlining words in their preferred colour,
i.e. word wall words or the students name.
Changing the background colour on a sheet
or creating a colour block for where they are
meant to write.
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Colour preferences are helpful in presenting
new information or for attracting a child’s
attention. However, the use of the
preferred colour should be phased out as
they become more able to look at new
objects and only be used when needed.
The goal is to use the colour preference to
teach new materials and colours, so
eventually the need for the colour will
resolve.
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Many children with
CVI will need
movement to see
an object or person,
especially if it is
unfamliar. This
may mean that the
object is moving or
that the child
themselves are
moving.
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Children may react
differently to
movement
depending on their
experiences and/or
the environment.
They may startle,
look away, become
quiet, smile or turn
to look at the
object.
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Most children are attracted to
movement. It can be in the form of a
moving object or in a shiny object.
The light moving over a shiny object
can give the impression of movement.
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Children can be over
stimulated by movement as
well. Such as in a crowded
gym or hallway. In this type
of situation, they may
appear to not use their
vision.
Shiny objects that produce
a relfection may be difficult
for the child to look at.
Children, cars or ceiling
fans moving can be a
distraction for a student
trying to use his/her vision.
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Visual latency is the delayed
response from the time the
target is presented, to the time
the target is visually regarded.
Visual latency decreases as CVI
resolves and can lessen when
CVI accommodations are in
place.
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Amount of latency can vary depending on the
student, the students general health, the
object or environment.
It is important to wait, stay quiet and not
distract the student while they are trying to
use their vision.
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Children may ignore certain visual
fields and they may have a preferred
visual field for looking.
Many children will prefer to use their
peripheral visual fields to see. Because
the peripheral visual fields do not
identify fine detail, students may react
more to general form or movement.
Children may have a mixed preferred
visual field preference, where they may
locate the object with one eye, but
examine it with the other or with one
field then another.
A central preferred visual field is rare.
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It is important to recognize a child’s
preferred visual fields, the head postures or
eye movements in order to be aware of when
the child is trying to use their vision and
when they may be avoiding the activity.
Christine Roman identifies three types of visual
complexity:
 Complexity of the pattern on the surface of
an object
 Complexity of the pattern on the surface of a
visual array (object within its surroundings).
 Complexity of the sensory environment.
Many children with CVI can not
look at toys or objects that have
complex patterns. Many baby
toys are bright and colourful with
many different patterns, sounds
and lights.
When an object is placed against a
visually complex background a child
with CVI can not find the object they
are looking for. This is often
referred to as visual crowding. This
phenomena makes organization of
materials very important.
Learning to read and separate letters,
then words can be very difficult
until this characteristic is resolved.
Why can he pick up the candy on the
floor, but he can’t find his bright
yellow teddy bear?
Some children with
CVI can only use
their vision when
they are not being
distracted by other
sensory input.
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A student who is using his/her vision may need to
stop using their vision in order to hear what is
being said, i.e. “good job”
Movement, noise or too much visual information
(crowding) can make it difficult for a student to use
their vision.
Present sensory information sequentially. Only add
other sensory information when the student is able
to handle the conflicting information.
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Children with CVI will often
spend long periods of time
fixating on light, but not on an
object.
Apparent visual fixation on an
object that is not there.
It needs to be determined if the
child is fixating on light in order
to stimulate vision or because
the environment is too complex.
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Children with CVI often can not recognize
even familiar objects beyond near vision
(40 cm).
When an object is moved further from the
face, the complexity is increased as the
background is added to the visual scene.
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Our visual systems are designed to alert to
something that is novel.
Children with CVI turn away from or will not
look at objects that are novel. They prefer
familiarity.
Preferred objects for
children with CVI
are often in their
preferred colour,
are visually simple
and/or reflect light.
To introduce new
materials or
activities, use the
familiar object to
bridge the gap.
Find materials with
similar qualities.
A blink reflex or a blink in response to a
visual threat are non existent or delayed.
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Students with CVI will often look
and touch an object as two
separate actions.
They may look, look away and
then reach or they may touch
without looking and then release
and look.
According to Christine Roman, they generally resolve
in the following order:
 Early resolution: light gazing, atypical or absent
blink reflexes.
 Middle resolution: Colour preference, visual
latency, difficulty with visual novelty, atypical or
absent visual reflex to visual threats, need for
movement.
 Later resolution: Visual field preferences, absence
of visualy guided reach, difficulty with visual
complexity, difficulty with distance viewing.
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