Convergence Insufficiency (CI) is the most common interference with maintaining precise binocular alignment in which a person’s eyes cannot be seen to turn. It is one of a class of conditions which produce similar signs and symptoms. Each of these conditions are treated with lenses, prisms, and/or optometric vision therapy. To be visually comfortable and efficient, binocular alignment must be within a ½ degree angle. Eyes that slip in, out, up, or down from this precise alignment compromise visual input. The effects are most obvious in reading due to the complexities of the task and the requirement for sustained ocular motor precision and speed. Eyes jump and stop to look four times a second while reading, or about 250 times a minute. When eye alignment drifts even minutely during these jumps, the eyes must realign at each stop or the degraded visual input will interfere with perception.
Because there is no obvious deviation of the eyes, these conditions are often overlooked. Problems are observed but it may not be realized that they are visual. Individuals, particularly children, may not report their visual disturbances because the disturbances are normal for them. A problem-focused history may bring them out. (See the Convergence Insufficiency Symptom Survey at the end of this blog.) Diagnosis of these conditions requires additional testing, beyond what is usually considered to be a comprehensive examination. Examinations which do not include this testing tend to add to the confusion when patients are told that there is nothing wrong with their eyes.
Convergence insufficiency causes a person’s eyes to not triangulate accurately and automatically for reading, writing, and using electronics. The system may work for a limited time but not have the stamina to maintain comfort, attention, and accuracy.
Convergence insufficiency rarely occurs in isolation. It is almost always associated with difficulty focusing and is often coexists with poor tracking. Like other neuromuscular coordination problems which lead to compensations, it is subject to fatigue. The problem is exacerbated by prolonged eyestrain. This occurs as the school year proceeds or after additional eyestrain at work over a period of weeks or months. Staring is particularly stressful. This happens to children when they must stare to decode words as they are reading. It also takes place in the early years of writing before making letters and words become automatic and children must stare at their pencil point as they are drawing letters.
Avoidance is the most common sign in children. For adults who find avoidance impossible, eye fatigue, headaches, and sleepiness are most common. When the limits are exceeded, double vision, blurring, and apparent movement of print can occur. Convergence insufficiency is common with post-concussion syndrome and is associated with amplified symptoms in this population.
Lenses, prisms, optometric vision therapy, and modifications of workstations and lifestyle are necessary to treat binocular vision dysfunctions. There must be adequate rest. Each visual system has its own tolerance for how long it can stare at illuminated screens without symptoms. Many work stations are set up poorly and people often do not take sufficient breaks. Children often have excessive homework in the early grades.
Adequate treatment requires that eye alignment, focusing, and tracking become automatic and sustainable for extended periods of time. Being able to consciously align your eyes is not adequate. We cannot think about our eyes and simultaneously think about what we are doing. Analogously, I can still run, but ball sports do not work well when getting to the ball uses attention needed for deciding what to do and doing it when I get there.
Optometric vision therapy uses techniques to develop accurate eye movements and perception supported by practice at home to develop automaticity. Trying harder may work for a time, but performance will be inconsistent and cannot be sustained. When treatment is continued to completion and appropriate visual habits are maintained, these problems should not recur.
Other blogs you may find interesting: