We have created this small subsection about lower visual field impairments because they can vary considerably from one person to another, as we show with the different examples below.
Please take the time to read each account. If you suspect a lower visual field impairment, it is important to also consider whether dorsal stream dysfunction is present, as they frequently occur together.
Connor is a little boy and has a lower visual field impairment. Connor's visual world varies depending on multiple factors including how noisy or busy the environment is, and how he is feeling. For Connor the same scene can vary considerably:
Connor has no visual awareness in his lower peripheral visual field. In addition to this, the clarity of Connor's vision (see visual acuity) is reduced from the midline down. Connor would be completely unaware that he was standing on the edge of a very steep hill.
The lower visual field in the above picture hasn't magically disappeared. Connor has no visual attention in this area. It is called visual neglect, which we will discuss in the following Assessing CVI sections.
The severity of the lower visual field impairment can range from person to person, for example:
Daniel and Connor, are two boys who have all the features of Balint Syndrome.
Recently, playing around the metal fence shown below, Connor tripped over the concrete feet of the fence, over and again. Daniel tripped over one once, then learnt and remembered, and did not trip over any of them again. Connor does not form memories from his lower visual field. Connor's lower visual field impairment has additional visual neglect, whereas Daniel's does not.
Gordon Dutton, in his blog 10 explained:
"Children with lack of the lower visual field commonly but by no means always have associated simultanagnosia."
For this reason, if someone has a lower visual field impairment, it may be a good idea to check for dorsal stream dysfunction or the more marked variant, Balint Syndrome.
Adam developed cerebral palsy when he was a young child. It was the type where he was late to walk because it affected his legs (called spastic diplegia). Adam was always being asked to walk standing up straight but insisted on looking down. Once Adam's lack of vision below the midline of his gaze was identified it became clear why he did this. Take a piece of card and put it just below your nose so you can't see down and try walking about. You'll soon realise why Adam insisted on looking down, it's the only way he can see the ground ahead of him. Now Adam has learnt to look ahead and look down in turn. Adam loves horse riding because he can sit up straight and doesn't need to look down. The horse does this for him.
Calum is a teacher. From an early age, he would never jump off a bench or into a swimming pool. He was unable to play hockey and hated sport. Calum talked about this with an expert in CVI one day who found that he was unaware of his feet whilst walking. Calum was surprised to learn that other people are aware of their feet. Calum explained that he had never really known where his feet are, but assumed that this was normal.
Lack of lower visual field can lead to:
to name but a few behaviours.
Some children with lower visual impairments show a love of climbing with no obvious fear of heights or falling. This could be explained because the potential fall is in their lower visual field, which they may not be aware of. For some, climbing back down is considerably more challenging.
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