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The child diagnosed with cortical visual impairment may not respond to the activities suggested for the light box in the same manner as a child whose vision loss is due to ocular abnormalities. The child whose vision loss is due to damage to the visual cortex and/or posterior visual pathways is said to have cortical visual impairment (CVI) (Groenveld, Jan & Leader, 1990). Other terms used to describe this type of visual loss include cerebral blindness, occipital blindness, visual agnosia, visual neglect, universal neglect and absolute scotoma (Morse, 1990). Damage may be caused by cerebral hypoxia; other causes include cytoplasmosis, toxoplasmosis, meningitis, trauma, and conditions causing cerebral degeneration. (Merrill & Kewman, 1986).
The literature suggest the following considerations may apply in performing activities on the Light Box with a child who has CVI.
- Intense visual displays and overstimulation of any kind should be avoided.
- Be very cautious about presenting any visual display with movements, shifting patterns, or flickering light. These may trigger a seizure in some children; consult the child's physician before introducing these (Groenveld, Jan & Leader, 1990).
- The child's cues should be carefully attended to, noting when he is ready for vision stimulation, and stopping when he shows signs of overstimulation or tiredness (Morse, 1990).
- Observation may give you some awareness of the length of time it takes for a particular child to process sensory information; use this awareness to time your presentation of materials and assist the child in organizing his responses (Morse, 1990).
- Surrounding distractions should be reduced (Morse, 1990). (The light box itself may be of some help in this regard since it is most often used in a darkened environment, reducing visual input from the rest of the environment.)
- Positioning the child so he is comfortable and secure means he will not need to divert energy to maintain his posture; this may be critical to his visual performance. (Groenveld, Jan & Leader, 1990).
- Taking care to introduce novel items gradually (Morse, 1990), and ritualizing the manner in which tasks are presented, using language to cue the child, and clearly marking the beginning and end of tasks may lessen the chances of overstimulating him (Groenveld, Jan & Leader, 1990).
- Visual displays should be simple in form and items should be presented separately or with adequate space between them, since children with CVI seems to have special difficulty discriminating between foreground and background information (Groenveld, Jan & Leader, 1990).
- Some children with CVI are sensitive to bright light; others require more light (Groenveld, Jan & Leader, 1990). The light box should be introduced at low illumination until you are able to determine the level that is comfortable for the child. It may be that the light box is not an appropriate tool for some children.
- Observe the child for field losses, which may be associated with CVI; modify his posture and your presentation of visual displays and tasks to accommodate such losses (Groenveld, Jan & Leader, 1990).
- Color may help the child with CVI perceive forms. Color perception is usually normal in a child with CVI, however, he may respond better to bright colors than to pastels, and yellows and reds may be easiest to see (Merrill & Kewman, 1986; Powell, 1996).
- It has been suggested that more severely affected children may relate better to common objects than to toys. (Groenveld, Jan & Leader, 1990). Common objects, both opaque and colored transparent ones, may be used on the light box to test this preference.
- REFERENCES
Groenveld, M., Jan, J.E., & Leader, P. (1990). Observations of the habilitation of children with cortical visual impairment. Journal of Visual Impairment & Blindness, 84, 11-15.
Merrill, M., & Kewman, D. (1986). Training of color and form identification in cortical blindness: A case study. Archives of Physical Medicine and Rehabilitation, 67, 479-483.
Morse, M. T. (1992). Augmenting assessment procedures for children with severe multiple handicaps and sensory impairments. Journal of Visual Impairment & Blindness, 86, 73-77.
Morse, M. T. (1990). Cortical visual impairment in young children with multiple disabilities. Journal of Visual Impairment & Blindness, 84, 200-203.
Powell, S. A. (1996). Neural-based visual stimulation with infants with cortical impairment. Journal of Visual Impairment & Blindness, 90, 445-446.
