Cortical Visual Impairment
By: MaryAnn Demchak, Charmaine Rickard & Marty Elquist
Purpose of this Tip Sheet
After reading this fact sheet you will have an understanding of:
- What is cortical visual impairment (CVI)
- Causes of CVI
- How CVI is identified
- Characteristics of CVI
- Implications of CVI
What is Cortical Visual Impairment (CVI)?
CVI refers to a brain condition, not an eye condition and results from damage to the visual systems in the brain that deal with processing and integrating visual information. CVI can be a temporary or permanent impairment and can range from severe visual impairment to total blindness. Because CVI is a neurological impairment, vision is more severely reduced than can be explained by an eye exam. The degree of the impairment depends on the age of onset as well as the location and severity of the impairment in the visual pathway. CVI is referred to by many different names including cortical blindness, cerebral blindness, central visual disturbance, and cerebral visual impairment.
Causes of CVI
The causes of CVI are varied (see Figure 1) with the most common causes being hypoxic or anoxic brain damage. Hypoxic brain damage results from the reduction of oxygen supply to a tissue, which can occur from cardiac arrest, resuscitated drowning, near miss S.I.D.S. (Sudden Infant Death Syndrome), and prolonged epileptic seizures. Anoxic brain damage results from the absence of oxygen supply to tissues and can result from asphyxia.
| Common Causes of CVI |
|---|
| Hypoxic brain damage |
| Anoxic brain damage |
| Developmental brain defects |
| Head injury |
| Infections of the central nervous system (e.g., meningitis & encephalitis) |
| Intrauterine infections (i.e., STORCH) |
| Progressive disorders (e.g., Tay Sachs) |
| And others |
Associated Diagnoses
Most children with CVI have other associated neurological problems. The most common of these include cerebral palsy, epilepsy, hydrocephalus, severe to mild learning difficulties, and seizures.
Characteristics of CVI
Children with CVI display a number of specific behaviors. Understanding these specific behaviors will assist individuals in appropriate interactions and interventions with children who have CVI. The following checklist will help to identify these specific behaviors; however, it is important to remember that children with other types of visual impairments may exhibit some of these characteristics as well. Please review the list below for characteristic differences between "pure" ocular and cortical visual disorders. While reviewing the checklist, here are some important facts to keep in mind about CVI.
- CVI can range from mild to severe.
- CVI can range from temporary to permanent.
- Many children experience improvement.
- Children with CVI can also have ocular (or eye) difficulties as well.
- Fluctuation is common.
- Characteristics can vary from child to child.
- A single approach does not work for all children.
- Children with CVI typically have some vision.
Appearance
- Does not look blind
- Lack of visual communication skills
- Nystagmus (rapid eye movement) rarely seen
- Blank facial expression
- Eye movements smooth, but aimless
Vision Function
- Visual function varies day to day/hour to hour
- Limited visual attention & lack visual curiosity
- Aware of distant object, but cannot identify
- Consistently looks to either side when visual looking
- Visual learning tiring
- Closes eyes when listening
- Balance improved with eyes closed
- Looks away from people and objects
- Spontaneous visual activity has short duration
- When visually reaching, looks with a slight downward gaze
- Uses touch to identify objects
- Turns head to side when reaching, as if using peripheral fields, or motion detection
Mobility Skills
- Occasionally sees better traveling in a car
- Difficulties with spatial interpretation
- Avoids obstacles, but unable to use vision for close work
- Unable to estimate distances
- Difficulties with depth perception, inaccurate reach
Improved Visual Performance When . . .
- In familiar environments
- Told what to look for & where to look
- Objects are widely spaced
- Color is used to assist in identification of objects or shapes
- Using familiar objects
- Objects are held close to eyes when viewing
- Looking at one object vs. a group of objects
- Objects are against a plain background and paired with movement and sound
| Characteristics | Ocular Disorder | Cortical Disorder |
|---|---|---|
| Eye examination | Usually abnormal | Normal |
| Visual function | Consistent | Highly variable |
| Visual attention span | Usually normal | Markedly short |
| Sensory nystagmus | Present when congenital & early onset | Not present |
| Poorly coordinated eye movements | Present when congenital & early onset | Usually normal |
| Rapid horizontal head shaking | Occasionally | Never |
| Compulsive light gazing | Rarely | Common |
| Light sensitivity | Dependent on the eye disorder | In 1/3 of the cases |
| Eye pressing | Especially in congenital retinal disorders | Never |
| Close viewing | Common, used for magnification | Common, used for magnification, a reduction in crowding, or both |
| Color perception | Dependent on the eye disorder | Preserved |
| Appearance | Appears visually impaired | Usually normal |
| Peripheral field loss | Occasionally | Nearly always |
| Presence of additional neurological handicaps | Fairly common | Nearly always |
From: Jan, J. E. & Groenveld, M. (1993). Visual behaviors and adaptations associated with cortical and ocular impairment in children. Journal of Visual Impairment and Blindness, 87, 101-105.
Strategies for Interacting with a Child Who Has CVI
Research has shown that visual attention is trainable where there is usable vision. In other words, children with vision impairments whose development is delayed need increased stimulation and interaction based on their residual vision. Strategies that can be adapted to the specific needs of children who have CVI include:
- Use simple cues (e.g., touch cues, object cues).
- Avoid figure-ground clutter.
- Use repetition & familiar routines.
- Avoid extra, unnecessary stimulation.
- If possible, pair visual information with other sensory cues.
- Do not over-stimulate the child with visual clutter.
- Be aware of visual preferences.
- Allow the child to avoid visual gaze if necessary.
- Be aware of other “drains” on energy.
- If needed, adapt the setting to reduce noise clutter, over-stimulating lighting, & other distracters.
- Sometimes moving an object will help the child to see the object better.
- Use real objects rather than abstract symbols (e.g., an orange vs. a circle).
- Use active rather than passive learning.
- Five environmental areas that can be changed to encourage children to use their vision:
- Color (bright vs. bland)
- Contrast (high vs. low)
- Lighting (use lighting cues--e.g., shining a flashlight on an object)
- Space/Distance
- Time (wait!)