Convergence insufficiency is a common problem of binocular vision. This disorder can affect children or adults but tends to be more common in childhood. Many adults may not feel the onset of symptoms until they get their first bifocal, get a job involving a lot of near-related visual work such as computers or go back to school to further their education.
Convergence Insufficiency can produce visual symptoms which also include blurred vision, double-vision, or jumbling and scrambled print as you try to read.
Convergence insufficiency occurs because of poor eye-teaming ability. Initially when we view something up close the lines-of-sight from each eye should cross directly where we look at. A tendency for the eyes to want to drift outward is present in individuals with this disorder. In order to to keep the image clear and single, more effort is required in order to concentrate on the task. This ever increasing effort is taxing and soon results in symptoms. This disorder can run in some families.
Blurred vision at near, eyestrain while doing near work, headaches, sleepiness while reading, double-vision, frequent loss of place when reading, inaccuracy while checking columns of figures or lists are common complaints. Severe cases can result in an eye turn.
A complete and thorough vision exam is required in order to detect this disorder. During this exam tests must be performed at a near distance in order to measure the eyes tendency to drift and how much ability the eyes have to compensate for this effect. If not performed this disorder can be missed by the doctor.
Vision therapy is by and far the most successful treatment available for convergence insufficiency. The goal of therapy is to build eye teaming ability to a level necessary to overcome the outward drift tendency.
Prism incorporated into an eyeglass prescription is a second option. Success with this form of treatment is much limited than with vision therapy. Very often adaptation to the new prescription occurs and the convergence insufficiency returns.
Alternatives include ocular muscle surgery however most experts do not support this mode of treatment today except in unusual cases.
Video on Convergence Insufficiency
Workstation Design Challenges
The patient with convergence insufficiency needs an efficient workstation design.
Our eyes are nearly always efficient with vertical eye movements (Y axis in illustration)
and usually efficient with horizontal eye movements unless a problem such as a saccadic dysfunction exists (X axis in illustration)
The Z axis is the most complex eye movement as it involves not only the eye teaming requirement of convergence but also an accommodative (focusing) change.
Workstation ergonomics goes way beyond the information presented here but a summary of placement of monitors should work upon (in priority)
Keeping the working distance identical for every monitor to minimize the z-axis differences
Keeping the monitors at equal levels of positioning. The example below shows the laptop lower than the full size monitor. Raising the laptop with a special lift or lowering the regular monitor would be more efficient.
Minimizing the horizontal distance between each monitor. The example below shows two different sizes which may be a common problem. Arranging the larger monitor above the laptop could be one consideration to experiment.
So many other dynamics exist that each case may need a specialized assessment. For example seating and posture, lighting, open or enclosed room / cubicle design, sounds, enviromental controls, and keyboard / mouse positioning and quality just begin to appear on the list of items to examine.