Convergence insufficiency is not a muscle problem – it is not that either eye cannot turn inwards; rather they are unable to turn inwards together, and sustain this posture. Occasionally the problem is congenital or occurs very early in life. However, almost always it is a fatigue problem caused by close work in susceptible individuals. One of the reasons for this may be that the child had never refined this ability. With the commencement of school work and learning to read, this problem becomes more apparent. Another reason can be that the visual system may be fatiguing and allowing one eye to drift out. In other words there is a breakdown in the ability to sustain near alignment of the eyes due to visual fatigue.
Individuals who have never refined the ability to maintain their eyes converged generally have very few visual symptoms. Children with this problem do tend, however, to have poorer fine eye-hand and visual motor skills and will tend to avoid near tasks as they have difficulty performing them. Those children who have acquired the convergence insufficiency problem tend to have more symptoms, particularly when doing prolonged near tasks. These symptoms may include, but are not necessarily limited to the following:
The management of the case and the duration of the treatment will depend on why the child has the convergence insufficiency problem. If it is because the child has never refined this ability, then a broader optometric visual therapy program will be required, of which developing convergence skills is but one aspect. In addition, glasses may or may not be required.
Treatment of acquired convergence insufficiency will generally require the prescription of glasses. In some cases, because these lenses reduce the visual demands on the visual system this is all that is needed to be done. In other cases, however, vision therapy will also be needed to rebuild and develop the visual stamina and convergence skills. It is important that the glasses are worn in the classroom as well as for all homework, reading, computer, or any prolonged close work tasks.
In an uncomplicated acquired convergence insufficiency case, a unit of vision therapy comprising of six in-office visits spaced one week apart, may be all that is required. For the developmental convergence insufficiency case, a longer period may be required to develop and teach all the required visual skills.
Often the reading glasses need to be worn throughout schooling years however they may be able to reduce their wearing time. Periodic follow up should be provided at least every 12 months during the child’s school life since the demands of the classroom increase throughout the school years.