Monday, 29 March 2010
Thursday, 25 March 2010
Cortical visual impairment (CVI) has a range of causes, including, but not limited to, lack of oxygen before, during, and after birth, viral or bacterial illness such as meningitis and cytomegalovirus, or traumatic brain injury.
CVI can affect vision in a number of ways and causes a variation of visual loss that can range from mild to severe, it can also be temporary or permanent. There is no way to predict how a child's vision will mature but many children who experience CVI do some improvement in their visual ability. Fluctuating vision is also experienced by many children, this being experienced mre commonly by children who also suffer epilepsy, or who are taking specific medications such as Dilantin, Tegretol, or Phenobarbital. This means a child may be able to see an object one day and be completely unable to the next.
Another cmmon feature in children who have CVI is that they may have better peripheral than central vision and thus look at objects out of the side of their eye. They may also experience problems with visual field loss which may not be symmetrical (one eye may be worse than the other).
Children with CVI commonly experience problems with specific types of visual tasks. They have difficulty with figure-ground (seeing an object instead of the background), and with complex visual displays such as cluttered pictures (a picture of five different animals instead of two). Spatial confusion is also commonly experienced; for example being unable to locate their chair even though they can see it. They may also be visually inattentive, not wanting to look at objects, and may prefer their sense of touch. It is common to see a child turn his/her head away as they explore an object with their hands. Seeing with CVI can be compared with trying to listen to one voice in a noisy room or to speaking a foreign language.
Can CVI be treated?
Yes, but with varying degrees of success. Snowdrop has treated children and completely restored their visual ability, but we have also treated children and seen little or no progress. Visual stimulation is proven to help most children with CVI as with other visual impairments and this can lead to improvments in the way they are able to perceive and use their vision. For visual stimulation to be effective it needs to be dramatic. We may not only be stimulating vision in the child, but also the way in which a child is able to use and switch his visual attention. This can only be done by giving the correct stimulation at the correct frequency, intensity and duration, in the correct therapeutic environment