Whew! Trying to find information on this topic has been the hardest thing! This is partially due to the fact that different doctors may label this condition with a different name. Neurological vision impairment, cortically blind, delayed visual maturation and cortical vision impairment (hereafter referred to as CVI) are often used interchangeably. Just for further clarification, neurological vision impairment is now the preferred term and the other three are labels depending on where in the brain the damage has been done.
A neurological vision impairment refers to the condition where the occipital lobe, the area of the brain that controls vision, is injured. When that part of the brain is damaged, visual images are not received. The actual physical condition of the eye can be normal, and yet the child cannot see or is visually impaired. This damage can be mild to severe, temporary or permanent, depending on the amount and exact location of the damage. Hypoxia is, of course, one of the top causes of this condition.
Children with CVI usually have other optical conditions. All of these conditions may also fluctuate depending on several factors such as fatigue, illness and medications. The most common of these are:
* Esotropia (also known as strabismus)-one or both eyes turn inward
* Exotropia (also known as strabismus)-one or both eyes turn outward
* Nystagmus-rapid or jerky eye movement (jumping eyes)
* Optic Nerve Atrophy-the nerves that carry the images to the brain may be atrophied (this is irreversible)
Binocular vision impairment is a condition due to strabismus that means loss of binocular depth perception. This is very common in children with cerebral palsy. The eyes do not aim in the same direction with this condition. This is also referred to as spatial confusion. For example, let's say a child has this binocular vision impairment, but is able to move. He or she can see the chair, but can't get in it, they might sit on the floor instead.
Fluctuating vision is common in CVI. Children may see one day and not the next. They may see one hour and not the next. It is very unpredictable. Some seizure medications, such as Dilantin, Tegretol, and Phenobarbitol can cause this fluctuation in sight or make it worse. It seems that most kids with CVI may have better peripheral vision than they do central vision. They appear to be looking to the side of you, when really, they are looking right at you. One eye may be stronger than the other eye, as well. It is so hard as a parent, when a child is labeled cortically blind, to figure out if or what your baby is actually seeing. This is an interesting web page that shows some examples of what children with damage to the optic nerve may see. It is not necessarily what our children see, but helpful in visualizing what their vision may be like. http://www.guidedogs.com.au/vision/corti...
