Cortical Vision Impairment- CVI

Students with CVI experience a vision loss that is not due to a structural problem with the eye, but a disruption in the brain function with seemingly contradictory results.  You might wonder how can the eye be almost normal and the child not see?  How can the child reach for a toy one moment and completely ignore and even brighter toy the next instant?  How can the child see an object and not know what it is? (From Cortical Visual Impairment in Children by Marieke Steendam)

CVI occurs when there is damage to the visual cortex or the posterior visual pathways or both places in the brain.  It is a unique impairment because it is an abnormality of perception and not an ocular disorder.  In general, the brain is receiving the visual information in a normal way, but the information is unable to be processed, organized or understood by the brain.  The visual cortex is the sight of this lack of perception that is also known as the occipital lobe of the brain.

Seeing is a process that is taken for granted.  Vision is the unifying sense.  We learn to see and understand what we see through experience, repetition, then grouping and interpreting information.  Children with CVI have difficulty grouping visual information into meaningful units.  For them, visual information is incomplete.

The visual cortex usually controls visual input by enhancing certain aspects of information and suppressing others.  The natural filtering system is damaged or lost in CVI students.  Since the visual cortex won’t suppress information, then touch and language are needed to quantify visual input.