Cortical Visual Impairment (CVI)

Cortical visual impairment (CVI) is an increasingly common cause of visual impairment in children in developed countries. It is commonly associated with other medical problems e.g. hearing loss, cerebral palsy, seizures. Children with CVI usually have structurally normal eyes. The problem lies with the parts of the brain that control vision. The amount of visual impairment can range from severe impairment to complete blindness.

CVI is caused by any process that causes damage to the brain.  Examples of these include hypoxia (lack of oxygen delivery to the brain tissues), developmental defects, stroke, infections e.g. meningitis, seizures, head injuries, hydrocephalus (increased pressure in the brain), and other neurological conditions.

How it affects vision

The extent of visual impairment is variable from child to child depending on the type and severity of the cause, when it happened in the child's development and which site of the brain was affected.

Common features of cortical visual impairment are:

• The level of vision does not stay constant and can change daily
• Poor attention and delayed responses to visual stimulation
• About 30% of children with CVI are very sensitive to light whilst the remainign two thirds appear to demonstrate a preference for looking at bright lights
• Vision improves when looking at moving objects
• Preference for looking at objects at close range or at odd angles

Prognosis

Visual function in children with cortical visual impairment is difficult to assess initially due to its variable and unpredictable course. It is also dependent on any other co-existing neurological and developmental abnormalities

Treatments that may be available

• The treatment of CVI is aimed mainly at early rehabilitation
• The care of children with CVI typically involves a multidisciplinary team of healthcare professionals and is tailored according to the child's specific needs
• Typically, the team consists of a paediatric ophthalmologist and/or neurologist, primary care physician, Physio and Occupational Therapists, Speech and Language Therapists and Orientation and Mobility Therapists.

The following visual stimulation has proven to be useful in children with CVI:

• Large, light reflective and moving objects
• Simple visual targets presented to the child at different angles
• Variable light levels
• Avoiding visual overstimulation
• Avoiding visual stimulation when the child is tired, irritable, hungry, upset etc.