Not all vision problems can be corrected by spectacles or contact lenses. Some people, including many children, have difficulty in coordinating their two eyes. In order to see something clearly, both eyes must be aimed correctly and focussed at the right distance. Any problems with the aiming or focussing of the eyes can cause a variety of symptoms, including intermittent double vision, blurred vision, headaches and feelings of eyestrain. Children with these problems often do not complain about them, but may simply avoid tasks such as reading which are difficult or cause discomfort.
Vision is the process of deriving meaning from what is seen.
Vision is not entirely innate but continues to develop after birth and is influenced by the visual environment and the individual's experience. If a person's visual system has not developed to its optimal level, visually demanding activities may lead to inefficient or uncomfortable vision. Good visual acuity and healthy eyes are no assurance that an individual does not have a vision problem. Each program of vision therapy must be designed to suit the specific needs of the individual. Diagnostic testing, training procedures and the use of lenses and prisms may be integral components of the successful treatment of a vision problem.