Convergence Insufficiency (CI) is a common binocular (two-eyed) vision disorder in which the eyes do not work at near easily. An eye teaming problem in which the eyes have a strong tendency to drift outward when reading or doing close work (exophoria at near). If the eyes do drift out, the person is likely to have double vision. Symptoms of Convergence Insufficiency include: eyestrain, headaches, blurred vision, double vision, inability to concentrate, short attention span, frequent loss of place, squinting, rubbing, closing or covering an eye, sleepiness during the activity, trouble remembering what was read, words appear to move, jump, swim or float, problems with motion sickness and/or vertigo.
There is a wide range of prevalence, particularly for convergence insufficiency in Spain and it ranges between 2.25–33 %.
A multi-site randomized clinical trial funded by the National Eye Institute has proven that the best treatment for convergence insufficiency is supervised vision therapy in a clinical office with home reinforcement (15 minutes of prescribed vision exercises done in the home five days per week). The scientific study showed that children responded quickly to this treatment protocol...75% achieved either full correction of their vision or saw marked improvements within 12 weeks. Another method of treatment include, Prismatic (prism) eyeglasses can be prescribed to decrease some of the symptoms. Although prism eyeglasses can relieve symptoms, they are not a "cure" and the patient typically remains dependent on the prism lenses. In addition, adaptation problems can lead to the need for stronger prescriptions in the future.
The ongoing researches on Convergence Insufficiency in Spain include: Prevalence of general binocular dysfunctions in a population of university students, Acid-sensing ion channels detect moderate acidifications to induce ocular pain.