Vergence Excesses
This is part 8 of the vision therapy series and will focus on vergence excesses—Convergence Excess and Divergence Excess.
If you have not read the previous portions of the vision therapy series, it is highly advisable that you review them as they cover information that will not be re-explained here.
This article will be a bit shorter than previous vergence articles as excess disorders are essentially treated with same vision therapy exercises as vergence insufficiencies, but opposite.
In other words, the exercises for convergence insufficiency will be managed similarly to exercises for divergence excess whereas divergence insufficiency exercises are often utilized to help individuals with convergence excess.
To learn about the different vision therapy exercises for vergence disorders be sure to check out Parts 6 and 7 of the vision therapy series—“What are Phorias, Tropias, and Fusional Vergence Dysfunction?” and “3 Advanced Exercises for Convergence and Divergence Insufficiency”.
Convergence Excess
Going back to the definitions of these disorders, convergence excess is a condition in which the eye muscle(s) over-respond to a given target at near. They tend to overshoot and will focus too far inward, or in front of, a target.
To put this concept into better light, if a person was focusing on a pencil 40 cm in front of his or her nose, their vergence system would respond as if he or she was focusing only 20 cm in front of his or her nose. The only way to avoid double vision in this circumstance is to have a high negative fusional vergence system to overcome the difference between the muscle response (20 cm) and where the actual target is (40 cm).
As you can imagine, over-converging can be quite draining on the system as it is constantly being overworked—think about trying to hold a 5 pound weight out in front of you for hours at a time, it would get exhausting!
Individuals with convergence excess often complain of headaches, fatigue, double vision, and avoidance of near tasks.
To treat convergence excess, the eyes will need to learn how to more accurately converge in response to a stimulus. It is also important for the system to learn how to diverge appropriately in circumstances when the system “locks-up” into an overly converged state.
Exercises used to help strengthen and fine-tune the vergence system to alleviate symptoms associated with convergence excess include pencil push-ups, Brock String, Lifesaver Cards, Aperature Rule, Eccentric Circles, Vectograms, Tranaglyphs, and Stereoscopes.
Exercises will focus initially on learning how to diverge, and then more accurately converge.
Divergence Excess
Divergence excess occurs when the eye muscles are stimulated to sit in an overly-diverged position (outward) making it difficult to converge to a near target.
Thinking back to the pencil target at 40 cm, individuals with divergence excess will try to focus on the target at 40 cm, but the muscle response will be that of a target at 60 cm, forcing the positive fusional vergence system to make up to 20 cm difference to avoid double vision.
Individuals with divergence excess also complain of double vision (when the fusional vergence system is unable to make up the difference) headaches, eye strain, and avoidance of near tasks.
The main difference in symptoms between an individual with convergence excess and divergence excess is that a convergence excess individual may complain that his or her eyes “feel stuck” when doing near tasks. He or she may notice that after doing near tasks things in the distance appear blurry as the vergence system is “stuck” in a converged state.
Divergence excess individuals, on the other hand, will feel like their eyes cannot move in enough—they physically cannot make their eyes converge to do near tasks, and will therefore often just avoid these types of tasks.
Therapy for divergence excess focuses on getting the divergence eye muscles to relax and stimulating the convergence eye muscles.
Exercises for divergence excess training are the same as convergence excess, however therapy will focus on learning to relax the divergence system and fine-tune the convergence system.