This study was performed to investigate whether vision therapy (vision training) was an effective way to influence fusional vergence and asthenopic symptoms in case of convergence excess. Patients who had esophoria at far and near had history and symptoms (horizontal diplopia, eye strain, asthenopia and blur). Among them for one chosen patient who had convergence excess, vision therapy and added plus lens were prescribed and trained for 7 weeks. 7 weeks later vision therapy was quite effective, that is, it was an effective means of reducing symptoms, improving fusional vergence and decompensating esophoria in patient with convergence excess. Therefore continuous research of vision therapy in binocular dysfunction was necessary.