convergence problems
To see clearly and without confusion at close distances the two eyes must be aimed precisely at the object you are trying to see.
Unfortunately not everyone develops this ability in childhood. Inaccuracy of the alignment of the eyes can result in visual fatigue, blurred or double vision, poor judgement of depth, eye ache, head ache and mental fatigue.
Convergence excess
Convergence excess is a condition in which a child’s eyes have a tendency to aim closer than at the object which the child is trying to see. It is possible to achieve correct aim only by exerting extra effort (Figure 1). Prolonged periods of close work can cause considerable discomfort.
Many cases of convergence excess are due to longsightedness. The need which longsighted people have to exert extra focusing (accommodation) to see clearly at close range has the effect of making the eyes tend to turn in too far, which creates the convergence excess.
Convergence excess affects about 10 per cent of school children.
Convergence excess can be treated with reading spectacles or bifocals which relax the convergence and focusing systems, removing the need for extra effort.
This often allows longer and more efficient concentration on close tasks. Eye exercises are not usually successful in treating convergence excess.
Convergence insufficiency
Convergence insufficiency is a condition in which the eyes have a tendency to aim farthur away than the object at which they are supposed to be pointed. Correct aim can be achieved only through extra effort (Figure 2 ). Convergence insufficiency affects about five per cent of children and up to 10 per cent of adults.
Convergence insufficiency is perhaps the simplest and most successfully treated eye co-ordination problem. Eye exercises are employed to train the eyes to aim efficiently without excessive effort. Normal convergence is usually attained after three or four weeks of daily exercises.
Spectacles may be a useful aid to treatment, especially where there is also a focusing problem involved, although on their own they will rarely solve the problem.
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