Vision for Doing
Assessing Functional Vision of Learners who are Multiply Disabled
Chapter 7 Assessing Vision for Doing
In the sections of this chapter, we set out different aspects of visual functioning and how to assess these.
For each section there is a diagram to help understand what we mean, and an explanation as to why to make observations of that type. This is followed by a description of what to do. The remainder of each section takes the form of trying to increase understanding of the meaning of your findings for curriculum design.
There are a few things to note about the way we have chosen to set out this chapter.
Least to greatest visual ability
The chapter is made up of ten related sections and a Summary Chart. Within each section there is a chance to compare specific aspects of information about the visual world. For instance in assessing the effect of difference in size, there is opportunity to record the effect of using different sized objects.
Not only is quantity of visual information our concern. We are also interested in the different qualitative aspects of visual information. Therefore sections help you to investigate the effects of intensity of light, size of objects, the effect of changes in contrast between an object and its background, how well the field of view of the learner is functioning, as well as other aspects of usual visual functioning. Taken together these correspond to functional vision or Vision for Doing.
By the final section a great deal of vision is needed in order to be able to respond to the activities suggested. At that point we refer the user to Appendix III.
NB In order not to confuse results between items, make sure that a stimulus used in an earlier item is not still present when trying the next item. For example, suppose you have just investigated the effect of bright sunlight. You now want to determine whether a light being switched on is noticed. If this is done while the sun continues to shine at the learner, any response would be ambiguous. The response might have been to the light or to the sun.
What? No sound?
It might seem rather obvious that this section of the protocol should be carried out with no sound associated. This is much more difficult to achieve in practice than it "sounds"! Rest assured that on those occasions when you find it difficult not to give a word of encouragement while carrying out the assessment, it only shows how important the whole person is to you and your style of working. When this happens (as it surely will), don't worry. Try again.
Making things easy
Two is company
Try to arrange a time when you will be able to have another person to help. It is very difficult to present the material, observe the presence of a response, and note it down - all at the same time. If there are two people, the tasks can be shared and a second opinion made available!
Time and place
We would suggest carrying out sections of this chapter as time becomes available. Do not attempt it all at once, otherwise you will never want to see it again! It is important to re- assess after a period of time as some visual improvement may occur as motivation increases and progress in other areas take place. On a more practical note, it is important to choose a time when there are as few distractions around as possible. Time of day will probably play a part in the learner's response due to a variety of factors: medication, feeding, tiredness.
The place is often problematic. Very few schools have a dark room or a suitable quiet room. If the room is unfamiliar it will be important to accustom the learner to it before assessment. As well as being able to control the lighting and noise level, the distraction level from wall or hanging decorations needs to be minimised, if it is not possible to eliminate it altogether.
The accompanying example (in the caption) gives an idea how your assessment will work.
Section 8 Observing the Learner's Eyes
Where to start
When working with staff in designing these guidelines they frequently commented that they had never really taken time to observe the learner's eyes. Now is the time to begin to do so.
First of all, make sure you know if the learner has an artificial eye. It wouldn't be the first time someone has tried to assess the vision of a glass eye! Also, does the learner normally have eyes open except when asleep? If they are normally closed, you will have a difficult task in one way. In another you will have learnt something without any effort - he won't see with closed eyes!
Pupils react to light
Observe the pupils of the eyes under normal lighting conditions, noting any unusual features, eg; constant small constrictions or dilations. (See Figure 7.8.1 for diagram of human eye). Then increase the amount of light and see if the pupil gets smaller. Decrease the light and see if the pupil dilates or gets larger. There are a number of ways of controlling the light, the simplest is to use a torch holding it at a distance of about 30cm. Switch it on, watch the pupil of the eye, then switch off.
Figure 7.8.1 The Human Eye
Should the pupil change in size this is a rough indication that there is light perception (LP). Only rarely will it be found that there is no change in pupil size as the level of light increases or decreases. Pupil response is a reflex action and is controlled by a different area of the brain from that which interprets what we see. However, reaction may be sluggish or variable between eyes and this will let you know that visual adaptation between light and dark will be slow. This will have an effect when moving from one environment to another - from dim light into daylight or vice-versa.
You may find a learner will show no constriction or dilation of her pupils when a light is shone towards her eyes. A few conditions exist which prevent movement of the pupil of the eye. This does not mean necessarily that the learner does not see. It may be helpful to use darker lenses in situations where the light is bright.
Begin by placing the learner in a position that she finds comfortable (if you are still uncertain as to appropriate positioning to prevent physical problems, you should consult with a physiotherapist or occupational therapist, as suggested in Chapter 5). Check that there is enough light in the room for you to see both eyes. Note whether the eyes are clear or cloudy. If the eyes are not clear it is likely that the information getting through will also be less than clear.
Eyes move together..
Here we mean that when the eyes move they tend to do so in a coordinated way. Should the eyes not move together this may be caused by muscle imbalance, which may in turn affect binocular coordination (the ability of the eyes to work together as a 'team. If this is the case, there may be several consequences. Difficulties may occur in judging distance. This could also affect mobility1.
Next try to determine if there is a squint or turn in one or both eyes. It is often difficult to tell which is the squinting eye because of the fact that you may be looking at the weaker eye when you think that the learner is focusing upon you. In order to decide which is the squinting eye, attract the learner's visual attention to an object, or your face, then cover one eye. An easy way to do this if the learner is co-operative is to hold a wooden or plastic serving spoon in front of the eye, if possible not touching it, as some learners do not like this. If the uncovered eye moves rapidly in any direction and stays there it is likely to be the squinting eye. Distress at having one eye covered may indicate it is the better eye or may just be pure annoyance!
Where you are still unsure if a squint is present then you could try the following technique. Shine a light into the eyes from directly in front and about 75cm to 1 metre distant. Note where the light is reflected from both eyes. If the two eyes reflect light from different positions, then it would be worth referring the learner for further testing by a specialist. Some conditions - such as aniridia, or no iris - make it very difficult for you to see the reflecting light.
The presence of a squint means that visual discrimination in that eye may not be so clear as in the other non-squinting eye (a condition known as amblyopia). Normally each eye has a slightly different image of a scene, with the brain fusing these into one image. With a squint this fusion cannot work as well. So one eye tends to dominate with information from the other eye being ignored. Otherwise two different images would be seen.
Where a squint is present in one or both eyes then it may be possible for the squint to be corrected. An operation is performed to bring the deviating eye into balance with the undeviating eye. It is an operation which, to obtain optimum results, needs to be carried out early in life - within about the first two years of life. Beyond this age, operating on the affected eye does not result in full use of vision. Between 2 and 8 years of age some visual benefit will be obtained. After this age the operation may be done for cosmetic reasons - to improve the appearance of the person. Any surgery carries risk. Medical personnel might then justifiably refuse to operate.
If caught in that predicament where the learner has a squint then two questions should be asked of the medical professionals. First, if this learner had no disabilities, other than the visual one, would the operation be carried out? Second, does this learner have additional complications which would pose a greater risk during surgery (such as heart defect)? If the operation would have been carried out had there been no other disabilities, and there are no additional complications (such as heart defect), then persist in requesting surgery. (Note though that there are other reasons why surgery may be inappropriate).
It is possible that one or both eyes has a squint. And the squint may only be occasional,or it may be present consistently. Squint is most common when it occurs with the eyes fixed on one distance, but absent when the eyes are fixed on other distances. If 'Occasional' is ticked then it is likely that the squint is noticed at times when the learner is tired. Good contrast of materials is useful when squint is present.
Now look to see whether the learner's eyes fix steadily when looking at an object. Uncontrolled trembling or oscillating movement of the eyes is referred to as nystagmus. These unusual movements of the eyes occur most often in a horizontal direction but can occur vertically or with a circular motion. Nystagmus is never a specific diagnosis, instead it refers to an effect caused by some problem. If nystagmus is present it may indicate a visual defect. Nystagmus rarely occurs in one eye only, we have, though, left space on the checklist should the nystagmus be present in only one eye.
It is normal for eyes to make very small movements as they fixate on an object or scene. Usually it is difficult to see these eye movements. The tremors described as nystagmus movements differ in being larger. There are different types of nystagmus. One type occurs when you see the eyes making wide sweeps first to one side and then to the other. Another type is where the wide sweep may occur to one side, to be followed by jerky movements back again. There may be jerky movements in a vertical or circular direction.
One effect is often to make it difficult to focus steadily on a word or details of a picture. The more the eyes oscillate then the more difficult it be comes to retain the image of the detail. You might also observe that the learner adopts unusual head postures when up close to pictures, Where this does occur don't discourage it, as it may be an effective strategy for seeing.
There are several different causes for nystagmus. The loss of central vision (vision for detail) at an early age (the younger the age at time of loss of central vision the more likely it will develop) may often result in nystagmus.
Transferring results to Section 18:
When you are finished this section move on to Section 9.