Cortical (Cerebral) Visual Impairment And Its Impact On Children With Cerebral Palsy
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When working with a child with Cerebral Palsy therapists need to look at the whole child and not just their motor skills. Therapists use sensory input to get a desired motor response. Vision plays a major part in a child’s motivation to move and explore their environment. Because there is damage to the brain in a child with CP there is a high probability that there is damage to the visual pathways leading to cortical visual impairment (CVI). Many eye doctors and vision therapists tend to be concerned with the eye structure itself and ignore the cortical impairment. Often eye reports state that there is nothing wrong with the eyes but parents are still concerned that their child is not looking at toys and seeing objects. As therapists we use toys and objects to help a child move and to interact with their surroundings. If the child is having a hard time understanding their environment then they tend to interact less with it. It is important we know how to adapt the surroundings so the child feels safe, secure and wanting to move.
Introduction[edit | edit source]
Cerebral Palsy is defined as brain damage during utero, delivery and the first two years of development. Many children with CP also have brain damage in the visual processing centers and visual pathways. Cortical visual impairment (CVI) is “a condition in which children have reduced visual acuity as a result of damage to posterior visual pathways.” (Skoczenski and Good, 2004). It is the most common cause of visual impairment in first world countries and is increasing in other countries.
The Brain and Vision[edit | edit source]
Sight as a sense is primarily associated with the eyes but vision is a complex system of the eyes and the brain. The visual stimuli are received by the eye and then are sent to the visual processing centers of the brain via the optic nerve pathway. It is estimated that over 40 percent of the brain is devoted to visual function (Dutton, 2006). The occipital lobes are primarily concerned with vision. The images are sent from the occipital lobes on to the temporal and parietal lobes to be integrated with other sensory input for identification. When there is damage to one or more of these areas then there damage to the visual pathways. However, there is a period of plasticity of the brain to improve visual function with best results between birth and three years of age.
Video: Cerebral Visual Impairment: A Brain-Based Visual Condition
Medical Conditions[edit | edit source]
The most common conditions associated with CVI are also associated with CP. These are asphyxia, perinatal hypoxic-ischemic encephalopathy, intraventricular hemorrhage, periventricular leukomalacia, cerebral vascular accident, central nervous system infection, structural abnormalities and trauma (Huo, Burden, Hoyt, & Good, 1999; Jan & Groenveld, 1993).
Click here for a helpful book on: Visual Impairment in Children Due to Damage to the Brain.
Diagnosis[edit | edit source]
Cortical visual impairment is diagnosed by 1) a normal eye exam that cannot explain the lack of functional vision; 2) a neurological medical diagnosis; 3) presence of unique visual and behavioral characteristics (Roman-Lantzy, 2007; Jan, Groenveld, Sykanda, Hoyt, 1987) A child can have an ocular issue along with CVI thus making it difficult to determine if the behavior is due to ocular or cortical condition.
The unique visual and behavioral characteristics of CVI are:
- Distinct color preferences – strong color preference, especially red or yellow
- Attraction to movement – need movement to obtain visual attention and sustain it; either the object or the child can be moving
- Visual latency – the child is slow in looking at the object
- Visual field preferences –uncommon field areas and maybe loss of visual fields
- Difficulties with visual and environmental complexity – difficulty viewing in a complex environment with other sensory input, including noise
- Light-gazing or nonpurposeful gaze
- Difficulties with distance viewing
- Absent or atypical visual reflex responses – blink reflex to approaching object is delayed
- Difficulties with visual novelty – tend to prefer looking at familiar objects
- Absence of visually guided reach – unable to look and touch an object at same time
Children with CVI have been described as seeing better some days better than others. This is not true. They see the same but the environment around them is different each day affecting their perception and functional vision.
