Sometimes, the extra-ocular muscles are taxed beyond their power to maintain single, binocular vision and can result in episodes of diplopia (double vision), or even to a point where using both eyes is not possible. When a convergence excess exists, it requires the muscle coordination system to work harder to maintain alignment of the eyes. “Distance” describes vision that is aimed at least 20 feet away.) (In this context, “near” means vision used for reading or computer work, usually at a distance of about 16 inches or 40 cm. Usually, this mismatch between where the eyes aim and where the object is located in space has more of an effect on vision up close, as opposed to looking farther away. “Convergence excess” is the term used to describe an eye muscle imbalance, which causes a tendency for the eyes to want to aim more inwardly than needed. But what happens when we converge too much? We need to be able to converge our eyes while eyes looking straight ahead are not normally converged, when we read something up close, our eyes must converge somewhat so we don’t have double vision. (In figure 1 we see a diagram of how the muscles are attached to the globe.) When they work as they should, in perfect synchrony, they help provide effortless coordination of the eyes at all distances and ranges of vision, all day long. Treatment duration will depend on the particular patient’s condition.There are six muscles attached to each eye called extra-ocular muscles that are responsible for moving the eyes in tandem in all directions. If vision therapy is required it usually consists of six in-office visits spaced one week apart, along with home based therapy between these visits. Therapy teaches better control but does not relieve the fatigue component. Visual therapy on its own does not work well to alleviate these problems. In some cases, vision therapy may be required in addition to the glasses. Usually over time prescriptions can be reduced and wearing time reduced. This is a therapeutic treatment that requires monitoring over time to ensure the excessive demand is reduced to within a normal range of focus and convergence. The lenses are typically worn for close work tasks such as reading, writing, computer work and copying from the blackboard. Management of convergence excess requires therapeutic prescription lenses to enhance the focus efficiency thus reducing the need to pull the eyes closer in. ![]() This leads to a mismatch between vergence and focus, thus affecting binocular vision accuracy. The eyes are aimed closer in than desired in an attempt to compensate for reduced focus stamina or focus ability. This excess of vergence is commonly associated with an accommodative insufficiency. When they get close enough to the page they may be using their ‘stronger eye’, thereby reducing the confusion and strain of trying to use both eyes together. Some children may move their book closer or forward to ‘see better’, when in fact what they are doing is trying to relieve their convergence excess difficulties. Rapid changes in convergence demands such as copying from the blackboard are often very difficult for children with convergence excess. Symptoms of convergence excess include eyestrain, headaches, blurred vision, double vision, sleepiness and (if reading) trouble remembering what was read. As a consequence, blur, confusion or fatigue may result.Ĭonvergence excess will effect near work tasks, especially reading and writing. Convergence excess describes a condition where the eyes do not exactly aim together rather, they aim too close or in front of the object.
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