CVI in Children: Implications for Orientation and Mobility

Amanda Hall Lueck, Ph.D.

AER O&M Conference

December, 2013

Much of this material will be available from

Lueck, A.H. & Dutton, G.N. (in press).Impairment of vision due to disorders of the visual brain in childhood: A practical approach (working title). New York: AFB Press

Overview

Terminology and background information

Who are the children with CVI

Different ways in which CVI manifests in children

Potential visual behaviors that may be compromised when a child is diagnosed with CVI

Implications for Orientation and Mobility

Who are the Children with CVI?

Profound visual impairment (the vision of some of these children can improve over time)

Functionally useful vision and cognitive challenges

Functionally useful vision who work at or near expected academic level for age (many of these children have normal/near normal visual acuity and minimal loss of visual field)

Ocular Visual Impairment:
A Quick Review

visual acuity

visual field

contrast sensitivity

color

light sensitivity

oculomotor

Vision is more than the ability to see details at near or distance

We are going to add to this list of areas when we talk about CVI, and also look at how impaired brain function rather than impaired ocular function can affect these areas.

visual acuity

contrast sensitivity

light sensitivity

visual field

color

oculomotor

CVI

Cerebral Visual Impairment

Increase in Numbers Worldwide

Improved survival rates of low birth weight preterm infants

reduced mortality rate of children with severe medical conditions

The visual system

involves both the

eyes and the brain

Caused by damage occurring in the optic radiations, occipital cortex, and visual associative areas of the brain.

Jacobson, L., Ek,,U. Ygge, J., Marburg, M. (2004). Visual impairment in children with brain damage: towards a diagnostic procedure. Developmental Medicine & Child Neurology. 46, 67-69.

Fazzi E, Bova S, Giovenzana A, Signorini S, Uggetti C, Bianchi P. Cognitive visual dysfunctions in preterm children with periventricular leukomalacia. Dev Med Child Neurol. 2009; 51: 974-81

Cerebral Visual Impairment

Can include impairment in

processing and analyzing information.

Visual perceptual impairments can exist with the typical ophthalmological dysfunctions related to acuity, field, and oculomotor issues, or

They can be the main clinical expression of CVI in children with normal or near normal visual acuity.

Fazzi E, Bova S, Giovenzan A, Signorini S, Uggetti C, Bianchi P. Cognitive visual dysfunctions in preterm children with periventricular leukomalacia. Dev Med Child Neurol. 2009; 51: 974-81

Good WV, Jan JE, Burden SK. Skoczenski A Candy R. Recent advances in cortical visual impairment. Dev Med Child Neurol 2001; 43: 56-60.

Location, extent, and age of onset of damage affects quality of vision

Who are the Children with CVI?

Profound visual impairment (the vision of some of these children can improve over time)

Functionally useful vision and cognitive challenges

Functionally useful vision who work at or near expected academic level for age (many of these children have normal/near normal visual acuity and minimal loss of visual field)

There are different ways to characterize how the brain works

Present a system proposed by Dr. Gordon Dutton to explain issues related to CVI based on work by David Milner & Melvyn Goodale

Additional information from Dr. Lea Hyvarinen

From Dutton, G.N. (2003). Cognitive vision: Its disorders & differential diagnosis in adults & children. Knowing where & what things are. Eye, 17, 289-304.

Goodale ,A, D., Goodale, M.A. (2005) Sight Unsee: An exploration of conscious and unconscious vision. Oxford: Oxford University Press.

Hyvarinen, L. (p& ersonal communication to FOVI, March 7, 2010) Cerebral/Cortical Visual Impairment C/CVI

LEFT HEMISPHERE picture of lobes of brain

Reflex Visual Pathways

Upper mid-brain (superior colliculi) and pulvinar

Reflex Visual Pathways

Ability to perceive and react to moving targets at a subconscious level

Some children still react to moving targets even though there is profound vision loss due to cerebral damage

Can see an object brought in from the side (blindsight) and can navigate without bumping into objects (travel vision)

Higher Visual Functions

What Happens to Information that Reaches the Visual Cortex?

Dorsal Stream “where system”

Ventral Stream “what system”

This is very simplified but can be very helpful in understanding functional consequences of CVI

Some people are also adding the “How System”

Dorsal Stream Disorders

Dorsal Stream processes the whole visual scene and works with the frontal lobes to give attention to areas of interest and plan motor action

Incoming information goes to:

Occipital cortex for processing

Dorsal stream sends the information to posterior parietal visual cortex where whole scene is processed and a part of the scene is chosen

This information goes to the frontal cortex which tells the head and eyes to look at the scene detail

The information coordinates are also sent to the motor cortex which initiates movement to toward the scene detail and causes other motor adjustments to interact with the objects in the scene.

Impaired visual search

Impaired ability to split intersensory attention

Lower field dysfunction (common in PVL)

Impaired perception of speed of fast-moving objects or rapid facial expressions

Impaired ability to split visual attention

Impaired performance in cluttered/patterned environments

Impaired auditory search and localization

Inaccurate visual guidance of movement of lower or upper limbs

Damage can result in disordered visually guided movements (children with PVL)

Difficulty moving through space, differentiating boundaries of floor surfaces,

Negotiating curbs, stairs

Inaccurate reach and grasp

(stereopsis may be intact)

Ventral Stream Disorders

Ventral Stream facilitates recognition of what is being viewed

Incoming information goes to:

Occipital cortex for processing

Ventral stream sends the information to temporal lobes which deal with visual recognition, orientation, and visual memory

If there is a match of information, an object is recognized

Ventral Stream Disorders

Damage can result in impaired

recognition of faces, facial expressions (commonly via right ventral stream)

Ranges from not recognizing familiar people to not recognizing these people seen out of context

Incorrect identification of strangers

Impaired recognition of objects (shape and form)

Difficulty with route finding-getting lost

Difficulty with visual memory tasks such as copying and learning information

Summary of Behavioral

Consequences of CVI

Behavioral Consequences of CVI

Visual Acuity

commonly reduced, but can be normal

Color and Contrast

can be normal, but both are likely reduced in most profound injuries

Behavioral Consequences of CVI

Visual Fields: depends on site of damage

Homonymous hemianopia (same side of visual field affected for each eye)

Bilateral lower visual field loss commonly associated with periventricular leukomalacia (i.e., damage to white matter around ventricles)

Behavioral Consequences of CVI

Visual Fields: depends on site of damage

Impaired ability to see two targets at same time leads to impaired attention*

Disability estimating depth (particularly moving feet through depth)*

*May give the impressionof visual field restriction

Functional visual field may vary depending upon the amount of visual stimuli present and degree of attention paid to fixation target in “formal” field testing

Behavioral Consequences of CVI

Control of Eye Movement

Eye motility problems

Strabismus

Nystagmus

Unstable fixation

Inaccurate fast eye movements

Deficient following eye movements (smooth pursuit)

Behavioral Consequences of CVI

Control of Eye Movement

Compensate for problems with visually guided eye movements using head movements

Behavioral Consequences of CVI

Accommodation Disorders

Incomplete accommodation to compensate for usual hyperopia (farsightedness) found in young children so that the retinal image is blurred.

If no accommodation, need to correct even small degrees of hyperopia

Behavioral Consequences of CVI

Perception of Movement

Impaired or absent perception of movement (children watch TV shows with limited motion, for example)

See only stationary objects

See only moving objects

Behavioral Consequences of CVI

Visually-Guided Movement Concerns

Difficulty moving through space

Difficulty seeing boundaries on floors

Difficulty negotiating curbs, stairs

Inaccurate reach and grasp

Motor planning

Behavioral Consequences of CVI

Object Recognition

Inability to recognize objects

Inability to recognize shapes

Inability to recognize faces

Inability to recognize facial expressions

Behavioral Consequences of CVI

Object recognition

Difficult with route-finding

Difficulty with visual-memory tasks -copying, for example

Behavioral Consequences of CVI

Visual Attention and Perception

May have ability to see but not use vision especially when tired, sick, upset or after taking certain medications

May not use vision to see in a particular area of vision (i.e., visual neglect)

May have difficulty seeing in a visually crowded environment, either up close or at a distance

May have difficulty shifting attention from one object to another

Behavioral Consequences of CVI

Global Picture vs Details

May attend to details of an object rather than the whole object itself

Dorsal Stream Dysfunction

Dorsal stream is immediate, unconscious automatic system used to appraise and move through the visual world

Dorsal stream issues more common in children than ventral stream issues

Dorsal stream functions are unconscious

Dorsal stream issues more amenable to change via intervention than ventral stream dysfunctions

Dorsal stream ranges in character and severity.

◦range of visual acuity and visual field

◦Varying degrees of CP

Common in children with periventricular white matter damage (PWMI), preterm births, Williams syndrome

Dutton, G.D. (2009). Dorsal stream dysfunction and dorsal stream dysfunction plus: A potential classification for perceptual visual impairment in the context of cerebral visual impairment. Developmental Medicine & Child Neurology ,51(3) p170-172

Ventral Stream Dysfunction

Ventral stream is the conscious recognition and orientation system which we are aware of and and which processes more slowly

Ventral stream is damaged less frequently than the dorsal stream in children

Ventral stream issues are usually associated with some dorsal stream dysfunction

Difficulty with recognition (due to visual memory issues

◦Faces

◦Facial expressions

◦Shapes and objects and their alignment

◦Navigating inside and outside (don’t know what you are looking at to orient)

Varies in degree and severity

Dorsal Stream Dysfunction Plus

Symptom complex of dorsal stream dysfunction results from a range of pathologies

◦Complexity of visual scene --Simultanagnosia

◦Sometimes impaired visual guidance of limbs --Optic ataxia

◦Possible reduced VA

◦Homonymous visual field impairment (often lower field)

◦Impaired face recognition

Balint’s Syndrome

Pathology of posterior parietal lobes due to ischemic pathology (due to loss of blood supply) identified by Rudolph Balint in adults in 1909

◦Optic ataxia –difficulty reaching for targets (poor visual guidance of movement of upper or lower limbs or body)

◦Apraxia of gaze- unable to move eyes to new position based upon visual cues (cannot move eyes to unseen detail)

◦Simultanagnosia -Spatial disorder of visual attention where can’t attend to more than one object at a time (see only one of two things at once)

◦Attention is gained when input is singular and without distraction

Macintyre-Beon, C., Ibrahim, H., Hay, I., Cockburn, D., Calvert, J., Dutton, N., & Bowman, R. (2010). Dorsal Stream Dysfunction in Children. A Review and an Approach to Diagnosis and Management. Current Pediatric Reviews, 6(3), 166–182.

Now finding posterior parietal injury in children manifesting clinically in similar ways as in Balint’s syndrome. Not all symptoms present and severity varies

Many of these children are educated in inclusive settings and their diagnosis is overlooked – thought of as clumsy, behavioral issues, overlook lower field impairment

Blindsight

Awareness of moving targets, lights, and colors in the blind area

Boyle, N.J., Jones, D.H., Hamilton, R., Spowart, K.M., Dutton, G.N. (2005). Blindsight in children: does it exit and can it be used to help the child? Observations on a case series. Developmental Medicine & Child Neurology. 47, 699-702.

In a retrospective analysis of 541 children aged 2 to 19 years in the UK

◦19 of the 32 children who had no light perception or light perception only had response to movement.

◦4 of the 70 children with hemianopia had response to movement

◦Especially noted in the peripheral field

There may be several anatomical sources for blindsight

Boyle, N.J., Jones, D.H., Hamilton, R., Spowart, K.M., Dutton, G.N. (2005). Blindsight in children: does it exit and can it be used to help the child? Observations on a case series. Developmental Medicine & Child Neurology. 47, 699-702.

Blindsight

Reponses included:

Smile

Reaction to moving light

Saccadic eye movements toward a moving target

Turning or reaching to moving target

Navigation around obstacles (travel vision)

Payne, B.R., Lomber, S.G., MacNeil, M.A., Cornwell, P. (1996). Evidence for greater sight in bilndsight following damage of primary visual cortex early in life. Neuropshchologia 34, 741-774.

Case study: Jason

CVI and Mobility

Many behavioral consequences of CVI can affect O&M performance

Which behaviors manifest in individual children will vary

Be on the lookout for the behaviors so that they are appropriately addressed in educational programs

Thank you!