University of Edinburgh

Functional Vision Assessment

Factors that can affect how well a person can see


I'm going to look at the factors that affect how well a person can see. Now these are the aspects that I would consider for children with no other difficulties. So this would generally be for children whose vision was their main additional support need. However for children with other additional support needs we also need to look at different things and I'll go over that in a moment. Now this is a list according to Andrew Blaikie who is a Consultant Paediatric Ophthalmologist. It's also the list that Dr Karl Wall uses in his Habilitation Programme. It's the list that I use on the postgraduate programme so this is the list that I'm familiar with. I'm just going to very briefly say what each of these is. So visual acuity; that is how clearly we are able to see detail. Visual field; and that's the area that we're able to see. The control of eye movements; we've all got very smooth, or most of us have very smooth eye movements. You need that when you're reading; you need it for looking. If you look at a very young child and roll a ball along in front of them, their whole head moves, up until they're about a year, when they're following it. That's a very simple test that you can use to see if the eyes are not working as smoothly as we would expect them to. You need to look at the light when you're working with children and the degree of lighting. There are meters that you can buy where you can test the level of light in a room but I usually use myself as the control. If the light is the same as it normally is for me then it should be the same for the child, and if I notice a difference in the way that they are working, then I would look at that in more depth. We would look at colour vision. We would look at contrast and Lynn is going to look at some of these assessments later. It's important that we know when the visual need became apparent. The reason I'm saying that is that we develop our vision at a very early age. So if a child hasn't had good vision from when they were a baby, they won't have any visual memory. They won't have any visual clues to fall back on. But if you or I were to lose our vision, now we have lots of clues that we would use. We know the shapes, we know the size of things. We know what colours are; and so we have a lot of visual memory. So that really influences the input we would have to young children and when we were assessing them. The severity of their visual need; we would get that information from the clinicians. The exent and use of their vision at an early age; so how soon were they getting support for their vision? Now in most local authorities children would be supported from birth, with a significant visual impairment. They would be identified at birth. But there are some authorities where, even now, they don't have any input from education or from a multi-agency team until they're in nursery. In my opinion that is far, far too late because you develop most of your visual skills in the first years of your life. More importantly you would work with the parents at that time and develop a good attitude so that they don't develop learned helplessness and have everything done for them. It is important. People will say to you "why are you working with that wee one, they're only 4 months old, what can you teach them? You're a teacher." Well no I won't be teaching the kids but I'll be working with the parents so that good practice is established from a very early age. And high expectations are in place from a very early age. Also it's very important that we take into account the level of cognitive development. Now that's a bit of a chicken and egg thing here because if they don't have good vision then that may influence their ability to develop good cognition. It can be that they have a visual impairment that they're not able to learn. A few years ago we had a working group in the Scottish Sensory Centre; I was part of that working group. We looked at cerebral palsy and visual impairment in children. That book is available on the SSC website if you want to have a look at it. And there is a chapter in there that Andrew Blaikie wrote; chapter 6. He's talking about assessment of visual function and how especially when you're working with children with cerebral palsy, you need to look at refractive errors and near focusing skills in more depth. Also to look at fast and slow eye movements. But that would probably be outwith our remit. I'm just telling you that so that you're aware that that's something he'd take into account. I said to you earlier the girl I had, her vision fluctuated on a day to day basis, especially if her general health was poorer. They may only cooperate with you for a very short time when you're doing a functional assessment. Also they will become tired very quickly and that's the same for a lot of children with a visual impairment. It is quite hard for them to use their vision for an extended period of time. Yet we sometimes say "take this work home with you and do it later". And they've already found it difficult to sustain near vision tasks. Then you say "just take it home, do it in the evening". So we really need to look at what are our expectations of these children? So it's possible and indeed I would say it's positive and good that only segments of a full assessment would be performed at any one time. You wouldn't go and do a whole battery of these tests in the one day because the child is going to be tired. And that's a luxury that we have that you don't have in a clinical vision assessment. It's possibly most meaningful, especially with children who have other needs, to do the assessment in a place that's familiar to the child. So either in a school; a classroom that they're familiar with or, for young children, at home. Some place that they are happy and relaxed.

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