University of Edinburgh

Vision for Doing

Assessing Functional Vision of Learners who are Multiply Disabled

Chapter 7 Assessing Vision for Doing

Section 15 Responses to Size Differences

Aims of Section 15

You will be interested in this section if you have established from the other sections in this chapter that the learner responds visually to objects. If you have not already discovered that some visual responsiveness does exist, you should return to do Sections 9 through 14 before embarking on this section.

You now want to find out the size of objects to which the learner responds. As we will see, however, any investigation you make of the effect of size must, in some way, also include the factor of distance. Rather than offering two quite separate sections, we thought it would be more intuitive for the reader if these were combined. In any case to some extent you have already observed the effect of distance from the object or event to the learner.

  • Responses to distance were observed in both Section 10, in relation to reflected light, and in Section 11 for approaching objects.

Knowledge of the effects of size and distance helps you to adjust materials so that they are more appropriate to the learner.

How to use

section 15

Large: furniture , large toys, balls, dolls, soft toys, clothes.

Medium: lego, duplo, small toys, smarties.

Small: hundreds-and-thousands, crumbs, beads, very small toys.

Begin by using large objects which offer good contrast against the background, and for which you have found the learner to have some success. Present objects in a position that you have found to work well (often this will be in the midline); begin with the object at around arm's length. After this use different distances and observe any inconsistency in the learner's responses at these distances.

What to observe

Refer to the diagram. The diagrams are not drawn to scale but are offered to give you an impression of what to observe. Above the dotted line you will see three diagrams which show the observations you will make. The top left diagram represents use of large objects. Below this represents use of medium sized objects. To the right is the use of small objects (these are placed on a table top).


the dotted line there is a table on which to record the results of your observations. The usual system is presented of Consistently (for consistent responses), Occasionally (where responses are present but not consistent), Never (for no response).

Cautionary Note

As we stressed before, remember not to allow previous items to influence subsequent items.

Transferring results to Section 18:

As with the other sections, you now have to decide what the results of your observations mean for the Summary Chart in Section 18. In that Summary Chart, you will find that in the row for Section 15 there is space to tick under a variety of boxes. It depends on which particular size of object you are using. Consistent or Occasional response to objects that are large size allows you to tick Aware. Consistent responses to medium size to tick Attend; and Consistent responses to small objects to tick Localise.

As before, if the learner makes a very specific response (eg; naming the object being presented), this would mean he could Recognise through vision. If you happen to have additional information by all means tick boxes in the filled areas as appropriate.

No response to objects of any size?

If he Never shows any response, try again on subsequent occasions with different objects and in different lighting conditions (that is in other Settings). You should still try the remaining sections in this chapter. If these too result in Never you should refer back to the curriculum suggestions in Sections 9, 10, 11, 12, 13 and 14. It would be unusual to have obtained responses to Sections 12, 13 and 14 without having any responses in the present section.

OR score localise if:

the learner Consistently notices objects that are of large, medium and small size. In this case go to the Summary Chart (Section 18), find row 15, and tick Localise. In this case it is very likely that you will be able to obtain additional information to show that he can also Recognise.

OR score attend if:

the learner Consistently notices objects of large and medium size, but not small objects. In this case go to the Summary Chart (Section 18), find row 15, and tick Attend. Try objects in different positions and note these for your own records. You will probably want to return to the suggestions for curriculum development given in this present Section as well as using the ones contained in other sections.

OR score aware if:

he shows responses only to large size objects. If so, go to the Summary Chart and tick Aware. Again trying different positions for objects and under different lighting conditions, noting optimum responses by the learner. Then move on to Section 16. You may well want to return and use the curriculum suggestions given in this present Section as well as those in previous sections.

AND score aware if:

you observe Occasional response to large or medium size objects.

Where to go now?

Having noted the results of your observations and transferred these to the Summary Chart, you are then ready to make a choice. The choice you make will depend on the results you obtained.


you can skip the remainder of this section and proceed directly to Section 16, dealing with assessment of visual responses to people. By doing this you will continue your assessment of use of Vision.


postpone further assessment and read the remainder of this section. In it we suggest activities for curriculum development.

Developing a curriculum

Improving awareness:

If from the Summary Chart you have found the learner to be functioning at this "level" then you should refer back to Sections 9 to 14 for suggestions on intervention. In addition there are suggestions to be found in Section 17 and the four sections that make up Chapter 6 (The Other Senses).

Improving attending:

The same argument applies as set out in the above topic 'Improving Awareness'. Refer to Sections 9, 10, 11, 12, 13 and 14 in this Chapter, and to the sections in Chapter 6.

Improving localising:

You will be interested in referring to the suggestions given here if the learner is found, from the Summary Chart, to function at the level of Localising.

Size and distance

When you come to think about it, Size must pose a bit of a problem for all of us. After all the size of an object's image on the retina (the 'camera film' at the back of the eye) will vary according to the distance of that object from the learner. How then can an object be seen as being of the same size despite being at different distances? As an example look at a small child about 2 metres from you. Now look at an average size adult 20 metres away. Which is bigger? Of course its a silly question. But its not so silly when you realise that the image of the adult on your retina is smaller than the image of the child on your retina. Where this works fine it is often known as size constancy. That is, we tend to see an object as being of the same size despite changes in distance from the viewer.

In the able sighted person size constancy may be regarded as being less of a problem than how we actually perceive distance in the first place. We have already pointed out (in Section 11) that this is not as simple as it might seem. After all the retina is relatively flat or 2-dimensional. How can it perceive distance in 3 dimensions? We saw that many different stimuli may be used to help in distance perception. And it is usually assumed that anyone (or indeed any animal) capable of perceiving distance should be capable of size constancy. However this may not be the case in those whose sight is impaired. In the case of the learner who is multiply disabled, there may be an even greater difficulty in perceiving size and distance correctly.

One of the things that may go wrong in the learner who is visually impaired is that his eyes may not adjust for changes in distance. As an object approaches an observer, the lens of the eye must 'bulge' in order to keep the object in focus. Those who are visually impaired from birth may well not have developed this ability. Their eyes may not accommodate to changes in distance. In your own observations of the learner try to discover whether greater difficulty is experienced when smaller objects are brought nearer to the learner.

In general you would want to present unfamiliar materials or new activities at a size that is known to be perceived by the learner and at a distance that is most easily coped with - often this will be in the midline but you should refer to Sections 10 and 13 to determine the most effective positions. We have in several places referred to this as compensating for the visual defect by making changes in the environment.

But you would also want to try to increase the range of sizes to which the learner does respond. When doing this use objects that are familiar and which are therefore most likely to utilise any abilities in size/distance constancy that the learner possesses. Clearly you will at some time reach the limit of visual ability.

Jumping jacks

Use a variety of four to ten centimetre objects placed into and out of containers. Continuancy toys like jumping jacks and 'worm in the apple' encourage attention to more complex detail.

Place an interesting toy or object in a box with a brightly coloured string dangling. Hold the box at the child's eye level and encourage him/her to pull on the string to make the toy jump out. Vary this by lowering the box so that she has to pull upwards for the object to appear.

Improving recognising:

You will be interested in following up this section if results in the Summary Chart suggest the learner is functioning at the level of Recognising objects and events in the world. You will probably have found Consistent responses to a range of sizes of objects.

"Peering close"

Often you will observe the learner who is visually impaired bringing objects up close to the eye or else moving so that his eye is close to the object. In this way a greater surface of the retina is covered by the image. It is important to appreciate that this does not indicate good accommodation. This may be quite the wrong conclusion to be drawn. For the learner may be preferring a large, but very blurred, image to a smaller, sharper image.

Use of computers

Information on places to obtain sugestions for use of computers is provided in Appendix II.

Improving understanding:

You will be interested in following up this section if results in the Summary Chart suggest the learner is functioning at the level of Understanding objects and events in the world. You will probably have found Consistent responses to a range of sizes of objects.

A child being introduced to the language of action could be shown a glove-puppet acting in some appropriate way; for example on the child saying "jump!" the puppet would do so. If this is successful, the puppet may be reduced in size, be hidden under, over, behind, inside other objects. Again use language appropriate to these concepts.

Concept building

Descriptive terms we commonly use in a sighted world constantly reinforce such basic concepts as in, on, behind, under, on top, big, small. To offer a similar understanding to the learner with severe visual disability we need to offer more direct learning experiences than those that can come through touch alone. As the vocabulary of a learner with multiple disability will often not be large, verbal descriptions need to be supported by cues from the other senses.

We have to be careful to identify for the learner the intended characteristics of sameness. For example, a yellow plastic model of a pussy-cat may look like a pussy-cat, but does not feel like one to the learner. It is very easy to confuse figures that look similar but do not feel similar while at the same time trying to teach the learner how to understand sameness.

Size may be explored through nesting pots and pans, plates, saucers and clothing. Also comparisons of large and small be given through people, chairs, portions of food. Over/under may be related to the branches of trees or in stepping over puddles. In/out given through boxes, different spoons in pots, seated in a car, placing feet in shoes and entering or leaving the house. Top and bottom can be given in relation to the body, shelves, drawers and clothing.

Refer also to Section 14 on contrast.

Use of computers

Information on places to obtain sugestions for use of computers is provided in Appendix II.

Testing visual acuity

If you have progressed to the point at which the learner can see small objects, you may want to proceed to carry out a simple test of visual acuity - ie; the ability to resolve detail. Although not highly precise the results you obtain could certainly be useful for the purposes of further curriculum development.

We would refer the reader on to Appendix III. There we discuss use of the BUST. This is a simple and reasonably accurate test of visual acuity carried out in the form of a game. The materials can be used flexibly, adjusting the manner of introduction to suit the learner. It is not appropriate for learners who are operating below the level of Recognising, and in fact is most suitably used with those functioning at the level of Understanding. Although we do not present the materials in Appendix III, we do offer a short and systematic guide to how to use the materials.