Cortical (Cerebral) Visual Impairment And Its Impact On Children With Cerebral Palsy

 

Introduction[edit | edit source]

Cerebral Palsy (CP) 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 centres 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.”[1] 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 sent to the visual processing centre of the brain via the optic nerve pathway.  It is estimated that over 40 percent of the brain is devoted to visual function.[2]  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 , it affects the visual pathways.  However, there is a period of plasticity in the brain to improve visual function, with the best results between birth and three years of age.

For more information on: Cerebral Visual Impairment: A Brain-Based Visual Condition, watch this video:

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 haemorrhage, periventricular leukomalacia, cerebral vascular accident, central nervous system infection, structural abnormalities, and trauma.[3]

Diagnosis[edit | edit source]

The diagnosis of CVI is made 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 behavioural characteristics;[4]
  4. A child can have an ocular issue along with CVI, thus making it difficult to determine if the behaviour is due to ocular or cortical condition.

The unique visual and behavioural characteristics of CVI are:

  1. Distinct colour preferences: strong colour preference, especially red or yellow;
  2. Attraction to movement: need movement to obtain visual attention and sustain it; either the object or the child can be moving;
  3. Visual latency: the child is slow in looking at the object;
  4. Visual field preferences: uncommon field areas and maybe loss of visual fields;
  5. Difficulties with visual and environmental complexity – difficulty viewing in a complex environment with other sensory input, including noise;
  6. Light-gazing or non-purposeful gaze;
  7. Difficulties with distance viewing;
  8. Absent or atypical visual reflex responses – blink reflex to approaching object is delayed
  9. Difficulties with visual novelty – tend to prefer looking at familiar objects;
  10. Absence of visually guided reach – unable to look and touch an object at the same time.      

Children with CVI have been described as seeing better some days than others. This is not true. They see the same thing but the environment around them is different each day affecting their perception and functional vision.     

The CVI Range[edit | edit source]

The CVI Range, developed by Christine Roman-Lantzy to assess the functional vision of a child with CVI with a specialised protocol, The assessment encompasses interviews with carers and teachers who know the child’s medical history and day-to-day schedule; observation of the child in their natural environment; and face-to-face evaluation. The Range looks at the child’s behaviour in all of the behavioural characteristics and the degree to which each of the behavioural characteristics interferes with the child’s functional vision.  The score is then used to determine if the child is in one of the three Phases of CVI:[4]

  • Phase I – Building Visual Behavior
  • Phase II – Integrating Vision with Function
  • Phase III – Resolution of CVI Characteristics

Once the Phase is determined, it can be used with the CVI Resolution Chart to determine environmental considerations that should be implemented and needs of visual development. 

CVI Chart.jpg

Phase I – A child tends to view a single colour (preference for red or yellow), needs movement to localise the object, is delayed in viewing, and tends to have a visual field preference. They attend to an object in a simple environment and do not regard the human face. Sounds and other sensory input hinder their visual attention. They might tend to stare out the window, at the lights, or at the fan. They might see an object across a room if it is novel to them.  Also, they do not look at the object while touching it.

Phase II – A child may now prefer two to three different colours but still need some movement to attend to the object, with visual field preferences decreasing.  Latency can still be present and increases when the child is tired, stressed, or overstimulated. They start to look at faces and objects further away and no longer stare at the lights. They start to reach for familiar objects while looking at it. 

Phase III – A child no longer has a strong colour, object, or visual field preference; latency, look, and touch are resolved. Auditory stimuli can be tolerated in a musical toy or in the room. Visual novelty and complex environments are still concerns 

Watch this video on Cortical Visual Impairment and the Evaluation of Functional Vision:

Therapy Implications[edit | edit source]

When working with a child with Cerebral Palsy (CP), therapists need to look at the whole child and not just their motor skills. Therapists use sensory input to get the 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 or seeing objects. As therapists, we use toys and objects to help a child move and interact with their surroundings.  If the child is having a hard time understanding their environment, they tend to interact less with it.  It is important that we know how to adapt to the surroundings so the child feels safe and secure, and wants to move.

Phase I: When working with a child with CP in Phase I, they need to be in a simple environment with subdued lighting and decreased noise; this includes no to minimal talking while having them look for the object.  Present the child with a toy that is one colour and has some movement.  Introduce the toy in a variety of visual fields and give the child time to respond.  Remember that your clothing presents a complex visual field, so wearing a black shirt and having it on a plain blanket or mat while working with a child in Phase I will decrease the complexity.  The therapist might use a red light-up ball to get a child to track and roll to their side, then to their tummy. 

Phase II – Use the same colour object in a variety of familiar places or start to use a couple of colours during therapy.  The child still might need movement, and the object might be shiny. They might still have a visual field preference and be slower in responding.  They might be able to tolerate people talking around them when they are not stressed or tired.  Visual complexity is still difficult, so limit toys with noise, lots of colour, and many toys around the child.  Have a child crawl towards a red ball and put it into a yellow container.

Phase III – A child in Phase III will now play with objects of different colours but might have difficulty with objects with a lot of detail.  Their preferred colour can be used to help them focus their attention in a complex environment. For example, placing red tape around their bedroom door when trying to get them to navigate their wheelchair through the doorway. They might still need movement or shininess for distance.  Continue to give them time to respond or find the visual field they need.  They can tolerate more noise around them and need someone to describe the consistent features of objects. 

For more information, take a look at this classic literature on cortical visual impairment:

References[edit | edit source]

  1. Skoczenski,A.M , & Good, W.V. (2004). Vernier acuity is selectively affected in infants and children with cortical visual impairment. Dev Med Child Neurol. 46(8):526-32.
  2. Dutton, G. N., McKillop, E. C., & Saidkasimova S. (2006). Visual problems as a result of brain damage in children. British Journal of Ophthalmology, 90(8), 932-933.
  3. Huo, R., Burden, S. K., Hoyt, C. S., & Good, W. V. (1999). Chronic cortical visual impairment in children: Aetiology, prognosis, and associated neurological deficits. British Journal of Ophthalmology, 83, 670-755.
  4. 4.0 4.1 Roman-Lantzy, C. Cortical Visual Impairment: An Approach to Assessment and Intervention (New York, AFB Press, 2007).