Cortical Blindness


Cortical blindness is the total or partial loss of vision. Although Cortically blind and Cortical visual impairment are basically the same thing usually if there is full vision loss it is referred to as cortically blind while if there is only partial vision loss it is referred as cortical visual impairment, CVI for short. Neurological vision impairment is also another medical term used and often one of the three terms are used depending on where in the brain the visual damage is affected.

Cortical blindness is not due to a problem with the eye, but is caused by the brain not processing the proper kind of information from the eye due to damage to the visual area in the brain, called the occipital cortex. The eye may appear normal and have normal reflexes like dilating and constricting in response to changes in light to the eye. This is because responses to light is a reflex.


What causes Cortical Blindness – Cortical visual impairment (CVI)?

There are many causes for cortical blindness, the most common is loss of oxygenated blood flow to the occipital cortex from either unilateral or bilateral cerebral arteries.

Other causes include stroke, surgery, head trauma, meningitis, some prescription drugs used to treat epilepsy can cause cortical blindness.

Symptoms of cortical visual impairment CVI, include visual ability that varies from one day to the next, depth perception, discrepancy in vision between the two eyes. The discrepancy in vision from one eye to the other will sometimes lead to one eye becoming more dominant while the other eye becomes weaker due to not relying on it as much. Due to the difficulties in depth perception, physical movements are often affected. For example, reaching for things will be impacted by lack of proper depth perception.

Some children and adults with CVI experience hallucinations and denial of blindness. Cortical blindness is often associated with cerebral palsy and different types of developmental delays.

Some children and adults suffering from cortical blindness are able to see moving objects but not stationary objects, while other cortically blind children or adults may be able to read a book but can not tell the difference between different faces. Some may be sensitive to bright light or like to stare into bright lights. Often sufferers of cortical blindness also have a delay to responsiveness to any visual stimulation.

Some sufferers of cortical blindness may rely much more on their peripheral vision than their central vision. Since much of a person’s activities and vision comes from the central and not peripheral spheres of vision, this may be why during therapy they may give inconsistent results to responses of visual stimuli. Often children or adults with cortical blindness are attracted to movement of objects in their peripheral vision.


Is therapy for Cortically blind or Cortical visual impairment possible?

Since cortical blindness and cortical visual impairment is caused by damage to that part of the brain that perceives images from your eyes, it is possible that partial vision may recover. It is also possible that sufferers of being cortically blind or cortical visual impairment may have this problem persist over a lifetime or fully recover.

There is no exact way to predict if a child or adult who suffers from being cortically blind will recover their vision. Every child or adult will have different vision problems, some cortical blindness may fluctuate on a daily basis between being able to see well to not being able to see as clearly as before.

Cortical blindness does not affect all children and adults the same way. Some sufferers of cortical blindness may recover fully while some people may recover vision partially with proper therapy.

Visual stimulation of the peripheral vision in recent studies has shown improvement in vision for children or adults that suffer from being cortically blind.

There are many different ways to help treat a child or adult who is cortically blind. It may not be possible to say that one thing alone will help. It will take a lot of patience and trial and error to find a therapy that will progress toward better vision. Through different therapy, once you find something that is helping the child or adult’s vision, it’s always best to use more of the therapy that is getting the better results as some therapies may just be not effective in helping regain better vision. When assisting a child with cortical blindness therapy, it will always be important to wait several seconds for a response to any visual stimulation and carefully interpret if that visual stimulation is working. There may be only a very subtle response from a child with cortical visual impairment, it may be difficult to tell whether they are responding to the visual stimulation.

Any type of cortical visual impairment therapy will have to be treated patiently as usually someone who has CVI will take a while to recognize even simple objects and faces, even after repeated exposure to the object or face. The process of recognizing an object to a child or adult with cortical blindness often will involve touching the object as well, often repeating the process of touching than looking. It may be hard for them to touch and look at the object at the same time as this may be too much information for them to process causing over stimulation.

Using the Maribelle Exercise Assist System may help someone that has cortical visual impairment. Movement is thought to help cortically blind people and we have had very good feedback from some of our clients noting visual improvement after therapy sessions in the Maribelle Exercise Assist System.