By MARY T. MORSE, Ph.D.
Special Education Consultant & Certified Teacher for Visual Impairments
Typically, we think of vision in terms of visual acuity or clarity of vision, visual fields, eye turns and tracking, scanning and fixation abilities. These visual behaviors are fairly easy to record but do not necessarily reflect the functional use of vision or the understanding of the messages the eyes receive.
Cerebral/Cortical Visual Impairment (CVI) is a brain based visual disability resulting from either (a) prenatal or postnatal insult to the brain or (b) how the brain organization became configured during its prenatal development. CVI effects how an individual understands the visual information received by the eyes. The location and extent of the brain insult determines which functional behaviors will be affected.
Damage to the visual brain can impair visual acuity, contrast sensitivity and may restrict visual fields. Damage to the higher visual processing centers may cause perceptual and cognitive visual impairments. Such damage may affect the outer brain tissue (grey matter or cortex) or the inner brain tissue (white matter), and lead to visual dysfunction with variations in nature and degree. The term cortical visual impairment, used to describe visual dysfunction from cortex damage, is rare in isolation. The term cerebral visual impairment (CVI) is preferred by the World Health Organization (WHO) to encompass damage to both the grey and white matter of the brain.
In children, CVI can cause multiple problems including impaired recognition of people, shape and objects, spatial orientation problems, difficulty handling complex visual scenes and inaccurate visual guidance of upper and/or lower limbs. Visual acuity may be normal or near normal in numerous children or it can manifest itself as total blindness in those with severe brain insults or insults to specific vision centers in the brain. The visual system may be the only part affected, or there may be associated damage to other brain structures. Some people with CVI have obvious visual and neurological challenges while others may appear as having no obvious difficulties – visually or neurologically.
Commonly Known General Characteristics of CVI Include
- Although CVI may occur as a single challenge, it typically co-occurs with other manifestations of neurological, behavioral or ocular problems. Depending on the nature of the co-occurrence, CVI frequently is overlooked even when, in reality, it may be the primary disability.
- There are wide variations in the functional use of vision. Some individuals demonstrate no visual responses at any times while other individuals have considerable use of vision and appear as fully sighted.
- There is wide variability in an individual’s ability to efficiently use vision on a consistent basis. These variations may be observed day-to-day or within the same day and same activity.
- There may be wide variations in regard to additional disabilities with possible impact of other ocular handicaps, medical and health problems, seizures, hearing, communication, self care skills, feeding, cognition, type of visual and auditory stimuli understood, interpersonal relationships, learning, etc. or
There may be no observable visual or neurologically challenges to the casual observer.
- There is wide variability within individual persons and between individuals in managing multi-sensory demands and planning/implementing fine and/or gross motor responses
- There is a tendency to use peripheral vision more than central vision. Depth perception difficulties also are common
- Persons with CVI have the tendency to look away when reaching
- Persons with CVI have the tendency to have associated central auditory processing problems. Most
- may be very interested in sounds
- may give the appearance of understanding all they hear
- may be particularly responsive to intonations and melody rather than actual words
Characteristics of CVI Not Commonly Addressed
Some individuals with CVI do not have obvious additional disabilities. These
individuals may be able to walk, care for themselves, talk, and have excellent
visual behaviors for some types of stimuli. However, they may have visually-based difficulties with specific stimuli and skills that are of neurological origin.
- Frequently said to be inattentive and distractible – sometimes labeled ADHD, PDD, autistic and/or behavior problem. These challenges may co-exist but frequently the visual processing disabilities, different from visual learning disabilities, may go undetected.
- These individuals may have difficulty or the inability
- to recognize objects – especially stationary objects
- to recognize and discriminate one human face from another (Remember: All faces have eyes, ears, nose & mouth and, thus, are structurally the same.)
- to recognize a human face as more than an object unless it moves or talks.
- to organize oneself spatially and to comfortably move through even a very familiar environment
- to recognize and use visual symbols which may include print, photographs and/or line drawings
- to recognize colors
- to point to various parts of their own body
- to distinguish left from right.
- to recognize other categories of stimuli (i.e., automobiles, animals)
Prosopagnosia and Facial Agnosia
A particular sub-set of individuals with CVI may have difficulty or the inability to
recognize familiar faces (Prosopagnosia) or difficulty or inability to recognize
any face, familiar or not (Facial Agnosia). Processing the human face is an
extraordinarily complex visual, neurological, social, and communicative
process. These individuals may have several of the following characteristics:
- May have different neurological sources causing the condition.
- May have variations between persons in brain imaging results.
- Will show variations even within this sub-group of persons with CVI. For example, may/may not have associated agnosias (not recognize objects and/or certain categories of objects and/or two dimensional visual representations and/or certain categories of two dimensional visual representations).
- May avoid visually fixating on the human face OR
- May stare intently at the human face OR
- May look toward only one part of the face (i.e., mouth) rather than the facial configuration
- May be able to name and/or point to various parts of the face but not recognize and identify the total configuration.
- May recognize some faces from one orientation, within context, but not be able to generalize that face to other orientations or situations.
- May want to touch people – especially their faces
- May not realize that they differ from others in recognizing faces
- May not understand the totality of language they hear but brighten considerably when language is combined with emphasized intonation.
- May understand language but have difficulty in using pronouns
- May use language but tend, at times, to “talk to the air”
- May have difficulty in discriminating one voice from another
- May have excellent short term auditory memory
- May not realize a person is present unless the person says something or moves
- May focus on a specific aspect of a person for identification (if they realize the person is present)
- May treat people as objects
- May have difficulty relating to peers
- May appear to prefer objects to people
- May have “subtle” additional disabilities such as fine and gross motor dyspraxia, social interactions, pragmatics of language, behavior, spatial disorganization
- May show definite ability to learn – especially colors, shapes, repeating alphabet
- May/may not have difficulty interpreting some/all types of two dimensional visual representation (very variable)
- Some may be able to recognize pictorial representations of faces but not be able to do so with tangible face
- May have difficulty managing multiple sensory-motor demands – frequently said to have sensory integration problems
- May have difficulty modulating their states of arousal.
- Perceptual impairments usually are an insufficient explanation for face-specific agnosia
- For many of the children, vision is their primary information gathering sensory modality in spite of the presented challenges
- Individuals who have the condition from birth may function better with the condition than those adults who suddenly acquire the condition due to some insult.
SOME DIAGNOSTIC STRATEGIES
- What is the visual diagnosis? Be especially sensitive to CVI, hemianopsia, optic nerve atrophy and/or optic nerve hypoplasia, ADHD, PDD and early onset of behavior problems
- What is the cause (etiology) of the condition? Be especially sensitive, but not limited, to strokes, meningitis, toxic shocks, right brain insults, occipital insults, prematurity, hydrocephalus, asphyxia, perinatal hypoxia ischemia, developmental brain defects, head injury, periventricular leukomalacia, shaken baby syndrome, traumatic brain insults and infections of the central nervous system such as meningitis and encephalitis.
- Have any types of brain imaging procedures been done? What are the possible implications of the results? The diagnosis is difficult and involves sophisticated perceptual tests, imaging techniques and interpretations.
- Parent reporting: For example, “doesn’t recognize…..” or “loves everyone and treats everyone alike” or “doesn’t seem to care much about people”, etc.
- School reporting: Plays alone; likes to be in corner or under table; difficulty managing states of arousal in open space; shows no reaction when parent comes to school; ignores peers; touches peers a lot and sometimes “hurts” them; looks at objects more than people; “nothing wrong with his vision – he can see everything”; does not make eye contact; stares intently at people; little “peculiarities” in his/her language; tends to touch others a lot.
- Systematic Observations: These observations need to be transdisciplinary and conducted over time, in many settings, under many conditions and, if possible, documented via non-edited videotape. The main point in observations is HOW the child does something more than if the child did a particular action. For example, does the child recognize the presence of people if they do not talk or move? Is the child able to identify people based solely on vision if the person does move? What does the child do in crowds? How does the child manage two-dimensional visual representations? How long is the child able to read before indicators of fatigue or behavioral problems manifest themselves. And much more.
Dennison, E., & Lueck, A. (Eds) (2006). Proceedings: Summit on Cerebral/
Cortical Visual Impairment: NY, NY: AFB Press
Dutton, G. & Bax, M. (Eds) (2010). Visual Impairments in Children Due to
Damage to the Brain. London, England: MacKeith Press.
Hyvarinen, L & Jacob, N. (2011). What & How Does this Child See? Elgin, IL: