Cortical Visual Impairment (CVI)
Definition and Incidence
Definition of cortical visual impairment
New field of research
Fastest growing visual impairment diagnosis
The Problem with Medical Diagnosis
Eye report frequently doesn’t say “CVI”
Best information may come from neurological
Test like MRI is not necessarily useful in diagnosing CVI
Look for “red flags”
Asphyxia-damage depends on severity & duration. Some causes: placenta previa, prolapsed cord, delivery complications.
Hypoxic Ischemic Encephalopathy-too little oxygen (hypoxia), too little blood flow (ischemia), irritation of the brain (encephalopathy). Results from asphyxia. Seizures common.
Cerebral Vascular Accident-(stroke) blood capillaries in the brain rupture, damage depends on extent of bleed, more common in full term male infants, mostly affects left side of brain, seizures common.
Intraventricular Hemorrhage-occurs in premature infants w/in 1st 48 hours. Severity grades I-IV.
Periventricular Leukomalacia (PVL)-something, such as trauma, occurs and oxygen does not get to the distant areas of brain. These die and become filled w/ fluid (sometimes called cysts in the brain). Can cause CP, developmental delays.
Infection-viral and bacterial (TORCH)=toxoplasmosis, rubella cytomegalovirus, herpes/HIV. Also meningitis.
Throughout this web exercise, please refer to:
Cortical Visual Impairment: An Approach to Assessment and Intervention, by Christine Roman-Lantzy, ©2007, AFB Press.
Unique Characteristics of CVI
Color: strong reaction/preferential response to a particular color, typically red or yellow. Color receptors are diffused through brain & almost all children have some color vision. Need their favorite color as a visual anchor.
Movement: Stimulates the “aware” system, gets the visual system activated. Movement w/out sound is generally easier to visually process.
Movement plus reflective qualities provide an invasive, difficult to ignore effect on the visual system.
Child may exhibit better than expected navigational skills.
Latency: delayed response to presentation of object. Can vary according to time of day, state of alertness, degree of stress, and neurological stability. Decrease in latency equals increase in visual behavior.
Visual Field Preferences: objects are more easily seen in certain parts of the visual field.
Especially in periphery, where movement is better detected by the retina.
Mixed field preferences: May use one eye for a field preference, and the other for verification.
Complexity: most interfering of all characteristics.
Target/object-some objects are too complex, and there is no place for child to anchor his vision and so vision shuts down: faces are very complex.
Array-what’s behind the object can cause problems even with preferred objects. This is responsible for the misconception that vision is variable. Actually, vision is constant, but background interferes with vision functioning.
Sensory environment-unable to process with more than one sense at a time; will defer to auditory over vision. Be careful where you place auditory stimuli. Limit talking while doing vision work.
Abnormal Reaction to Light-Photophobia/Light Gazing/Non-Purposeful Gaze-prominent in early stages.
Distance Viewing-As object gets farther away, complexity increases. Makes child appear nearsighted.
Visual Reflexive Responses-absent, intermittent, or delayed blink reflex. Blink to threat; blink when you touch the bridge of the nose.
Visual Novelty-strong response to familiar objects. Appear to ignore novel items.
Visual Motor-look and touch may happen as separate events.
Resolution of Characteristics
Best chance for resolution is within first 3 years, but the possibility for resolution continues to exist into adulthood.
Characteristics will not resolve without structured intervention
Phase I: Building visual behavior
Phase II: Integrating vision with function
Phase III: Resolution of all CVI characteristics
"When a child with CVI needs to control his head, use his vision, and perform fine motor tasks, the effort can be compared to a neurologically intact adult learning to knit while walking a tightrope." http://www.tsbvi.edu/seehear/fall98/cortical.htm
Introduction to Christine Roman-Lantzy’s Assessment
Assessment Framework
Interview
Observation
Direct evaluation of student
Reliability
The Reliability of the CVI Range: A Functional Vision Assessment for Children with Cortical Visual Impairment, by Sandra Newcomb, Journal of Visual Impairment & Blindness, October 2010, © 2010 AFB.
Parent Interview/Teacher Interview
Information on medical background
Eye report
What does child like to look at
What are your concerns
Child’s favorite color
When is child most visually alert
Does child look directly into faces
Does child notice things that move more than things that are stable
Does child seem to look “through” rather than at objects
Observation of Vision
In living and learning environments
Quiet and noisy times
Near and distance
Familiar and unfamiliar objects
Cluttered and simple backgrounds
Interest in objects of specific color (color preference)
Movement
Light gazing
Preferential viewing
Direct Evaluation
Evaluate range of visual functioning
Evaluate presence and degree of individual CVI characteristics
May need several sessions to test
Forms
Parent Interview questions are on page 34 of book.
Answer Guide to Parent Interview – page 41, appendix 4a.
Rating 1– Across CVI Characteristics Method – Figure 5.2, page 57
Rating 1 – CVI Scoring Guide – page 97, appendix 5a.
Rating 2 – Within CVI Characteristic Method/CVI Resolution Chart – Figure 5.6, page 75
Essential Forms are listed beginning page 18
出處：http://www.tsbvi.edu/cvi-exercise/cvi-intro