CVI Mascot - VIC

Resources

CVI v OVI & Neuroplasticity Paper

CVI v OVI & Neuroplasticity Paper

Cerebral versus Ocular Visual Impairment: The Impact on Developmental Neuroplasticity
Journal - Frontiers in Psychology

This paper (link above) considers the difference between the brain's development where there is lack of vision from the eyes (ocular visual impairment) as opposed to the brain (cerebral visual impairment). It raises some really interesting points that we wanted to share.

  • Due to improvements in medicines, treatments and surgical techniques, ocular visual impairments (OVI) are decreasing.
  • Due to improvements in neonatal care for premature babies, cerebral visual impairments (CVI) are increasing.
  • Cerebral visual impairment is the leading cause of visual impairment in children in economically developed nations.

So, what are the differences where vision loss is due to the eyes or brain? Do the same strategies apply and work for both? This paper argues not, and found that:

"educational strategies designed to increase independence and functionality in children with ocular visual impairments are largely ineffective, and perhaps even detrimental, when applied to children with CVI"

We share this view. For many CVI is understood in terms of

  • low vision
  • reduced vision
  • absence of vision

In our experience...

  • Difficulty or inability giving visual attention
  • Inconsistent vision
  • Inaccurate vision
  • Unreliable untrustworthy vision
  • Frightening vision

...need to be added, for many affected children

The paper notes in relation to CVI:

"Most striking, however, are impairments in visual processing and attention which have a significant impact on learning, development, and independence."

We know that many children with CVI are affected by reduced visual attention, please see our Simultanagnosia Spectrum sections for more information. The Visual Acuity Simultanagnosia Problem section is an example of the ineffectiveness of an approach focusing on low vision, where a child also has reduced visual attention.

Historically, the majority of vision research has focused on conditions affecting the eye and optic nerve. CVI, with little understanding, was initially tagged onto OVI and we know from speaking to teachers of the visually impaired how difficult it was, even twenty years ago, working with children who had CVI with very little guidance, having to "muddle our way through".

Today there is much more understanding, but it is a complicated condition, and it cannot be understood without a basic understanding of how the brain processes vision.

The paper states the importance of

"accurate descriptive terms to characterise and localise the site of the brain based injury".

This means that rather than use umbrella or generic terms, like CVI, or MDVI (multiple disabled with visual impairment), the exact nature of the condition needs to be understood in terms of each individual cerebral visual impairment for each individual person. We have repeated this many times, that CVI is so completely unique to each individual child that generic approaches are inadequate. As Gordon Dutton once said

"when you've met one child with CVI, you've met one child with CVI"

We couldn't agree more, and our entire website follows the visual brain, and tries to explain, without using technical language, the different areas of the brain that are affected with individual cerebral visual impairment (many of which are further spectra).

You can't understand CVI without understanding the visual brain.

You can't understand the brain without understanding the visual brain.

You can't understand CVI without understanding the visual brain.

The research behind this paper looked at images of brain activity comparing persons with:

  • normal vision
  • ocular (eye) blindness from a young age and
  • CVI

The findings are fascinating, because the eye blind seem to create new pathways in the brain to compensate for their vision loss

"The brain undergoes dramatic structural and functional changes in response to ocular blindness"

This is wonderful for those with ocular blindness and shows how effective habilitation and rehabilitation strategies have been, to allow such development, so that the individual may lead a full and independent life.

But what about CVI?

Not all children with CVI have a diagnosis of CVI, but even where they do, many of the accommodations and strategies are still based on an understanding of low vision, which historically comes from an understanding of low vision in terms of ocular visual impairments.

We know better now and this needs to be extended and customised for our children.

Figure 1 Images

Please click here to view the images that are Figure 1 of this paper.

These three images show the visual pathways in the brain where affected people have:

  • a. Normal sight
  • b. OVI
  • c. CVI

Without knowing anything about the images, the pictures show the considerable impact CVI has on the brain.

The images show the occipital cortex, and three visual pathways.

  • SLF (superior longitudinal fasciculus) - This pathway starts at the occipital lobes and conducts the dorsal stream, continuing through to the frontal lobes. Fasciculus means bundle of fibres.
  • ILF (inferior longitudinal fasciculus) - This pathway starts at the occipital lobes and conducts the ventral stream and continues through to the frontal lobes.
  • IFOF (inferior fronto-occipital fasciculus) - This pathway runs from the front to the back of the brain connecting eye movements with attention. The frontal lobes are where our conscious attention is and decisions are made. Sometimes it is called the 'executive function' or 'control panel'. The frontal lobes have been fed information from the dorsal and ventral streams, as extended to SFL and ILF above, and thinks... "I wonder what that movement over there is, I'll look" and thus a signal is sent back along the IFOF to a bit of the brain deep within the occipital lobes that instructs the eyes to follow the target.

For us this highlights a number of key points:

  • CVI should never be considered an extension or variant of OVI.
  • CVI needs to be considered beyond a mere understanding of low vision.
  • CVI is the leading cause of visual impairment in children in the developed world, and the training of all professionals who care for children with visual impairments should reflect this (currently CVI is an inappropriately small, and sometimes optional elective)
  • We know that if the unique individual nature of the child's CVI is identified and understood, with suitable accommodations making learning accessible (see our Access section for more information), the potential for affected children is without limits.

This seminal paper shows that much of the brain is affected in children with CVI. It is clear that all efforts to teach affected children need to take this new knowledge into account by understanding and accommodating the needs of 'the whole child' and not just their vision.

Cerebral versus Ocular Visual Impairment: The Impact on Developmental Neuroplasticity
Frontiers in Psychology

The Laboratory for Visual Neuroplasticity, Harvard Medical School

HELP SUPPORT US

Your generous donations will be put to immediate use in supporting our charity...

Donate Here

About Us

At CVI Scotland we are devoted to helping people understand cerebral visual impairments, and together working towards developing the understanding of this complex condition.