Convergence insufficiency (Ci) is the way we describe a person’s inability to converge and aim their eyes at a near target when doing close work eg. reading, writing, computer, etc. There is a breakdown in the ability to sustain the near alignment of the eyes often due to visual fatigue.
The first point to make is that the person (usually a child) does not have a muscle problem. They are unable to co-ordinate the two eyes well enough when they are required to look inwards, and sustain this posture for long enough. Occasionally the problem is thought to be congenital or may occur very early in life and one of the reasons for this may be that the child never refined this ability. This is often a fatigue related problem that affects susceptible individuals and is caused by sustained near vision. The problem generally becomes more apparent with the commencement of schoolwork and learning to read.
Individuals that have never refined the ability to maintain their eyes in the converged posture may have very few visual symptoms. These children do however have poorer fine eye-hand and visual motor skills and will tend to avoid near centred tasks as they have difficulty attending to these. They may also require more tactile involvement (feeling) in learning about their world than would be expected for their age.
Those children that have acquired convergence insufficiency tend to have more symptoms, particularly when doing prolonged near centred tasks. These symptoms may include, but not necessarily limited to the following:
- Difficulty sustaining attention at visually demanding tasks.
- Visual fatigue or stress symptoms such as red eyes, sore eyes, frontal or temporal headaches, transient near and/or distance blur.
- Occasionally a child will also complain of double vision or the letters moving or running (swirling)
- Abnormal postural adaptations when trying to centre on near tasks, including head tilting or holding their work very close.
- General fatigue and orbital pain around the eyes.
The management of the case and the duration of the treatment will depend on the cause. If it is because the child has never refined this ability (Developmental Ci), then a broader optometric visual therapy program will be required. Spectacle prescriptions are often not required in these cases.
Acquired Ci will often require prescription spectacles to reduce the demands on the visual system and this may be all that is needs to be done. Some people benefit from concurrent visual therapy to rebuild and develop the visual stamina and convergence skills. It is important to wear these glasses in the classroom as well as for all homework, reading, computer, or any prolonged close work tasks to protect the system from the effects of excessive fatigue. There are special lens designs available to moderate the effects of visual stress and fatigue.
In an uncomplicated acquired convergence insufficiency case, visual therapy may take between 4 to 6 office visits which are usually spaced 2 weeks apart. For the developmental convergence insufficiency case, a longer period may be required to develop and teach all the required visual skills.
Periodic follow up should then be provided every 12 months during the child’s schooling life as the demands of classroom tends to increase throughout school years.
SCOURCE: The Australasian College of Behavioral Optometry [www.acbo.org.au]