Video for VI Learners
Effects of visual impairment
Difficulty changing focus
What is meant by Problems with Changing Focus?
Normally while watching videos on a screen you don't need to change
focus, as the main action or object of interest is usually captured
in clearest focus for you by the camera.
However, in the educational setting where there may be a lot of other
things going on in classroom or lecture hall you may be called upon
to focus your attention (and eyes) on different things. You may be asked
to look at a list of items on an overhead projector screen and then
see how many you can identify from a video excerpt.
Difficulty in focusing and refocusing is usually related to one or
other of the following:
- eye muscle problems
- lack of elasticity in the lens in the eye
- refractive errors caused by the shape of the eye eg long sight,
short sight, astigmatism.
What effects does difficulty in changing focus produce?
Some people can't avoid changing spectacles or magnifying lenses to
adjust between objects in the near, far or middle distance.
If you need to use a monocular or binocular
it takes some time and a good deal of skill to find and focus on the
object person or text through it, even if you know their rough whereabouts.
If you have a an eye condition causing restriction of the visual fields,
it will be very difficult to find visually the person or object on which
At certain distances you may have to put up with a blurred image, particularly
if, by the time you manage to focus, the object or person moves off
All of the above slow down learning processes and impede concentration.
What general situations make this worse?
Focusing and refocusing is very tiring if you are having difficulties:
long sessions with many focus changes don't help.
Using any kind of low vision aid increases the workload and associated
If the environment is very busy and the lighting conditions are not
suitable for your needs that can often worsen the situation.
How does this affect video screens?
Whether you have your own individual monitor or a group monitor or
a central screen it is better if you don't have to keep focusing and
refocusing on different areas of the class or lecture hall. Careful
positioning of the student helps, keeping all people and teaching aids
within a small search angle.
What would improve access to video (and other educational resources)?
Several practical things can be done:
- use appropriate glasses or low vision aids;
- ask for your own copy of overhead material;
- suggest best positioning for different audio visual aids and the
- view the video beforehand or ask if you can go over the work after
class to have more time.
What names of eye conditions
should I look out for?
- myopia (short sight)
- hypermetropia (long sight)
- retinitis pigmentosa (tunnel vision).