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The symptoms and signs associated with convergence insufficiency are related to prolonged, visually demanding, near-centered tasks. They may include, but are not limited to, diplopia (double vision), asthenopia (eye strain), transient blurred vision, difficulty sustaining near-visual function, abnormal fatigue, headache, and abnormal postural adaptation, among others.
Seeing 3D movies can increase rating of symptoms of nausea, oculomotor and disorientation, especially in women with susceptible visual-vestibular system.This is caused by a “disagreement” between the vestibular system and the visual input, causing that the body interprets it is moving, creating a contradiction with the vestibular system. [5]
Accommodative insufficiency (AI) involves the inability of the eye to focus properly on an object. Accommodation is the adjustment of the curvature of the lens to focus on objects near and far. In this condition, amplitude of accommodation of a person is lesser compared to physiological limits for his age. [ 1 ]
Accommodative excess may occur secondary to convergence insufficiency also. In convergence insufficiency near point of convergence will recede, and positive fusional vergence (PFV) will reduce. So, the patient uses excessive accommodation to stimulate accommodative convergence to overcome reduced PFV.
Suppression of an eye is a subconscious adaptation by a person's brain to eliminate the symptoms of disorders of binocular vision such as strabismus, convergence insufficiency and aniseikonia. The brain can eliminate double vision by ignoring all or part of the image of one of the eyes.
Vergence control, and over-convergence associated with the extra accommodation required to overcome a hyperopic refractive error, play a role in the onset of accommodative esotropia. The classical explanation for the onset of accommodative esotropia is a compensation of far-sightedness by means of excessive accommodative convergence.
A large-scale randomized clinical trial known as the Convergence Insufficiency Treatment Trial (CITT) found that office-based vision therapy combined with at-home therapy was more effective than placebo therapy (in-office placebo treatments) for improving symptoms and clinical signs of convergence insufficiency in children and adults.
Presbyopia, physiological insufficiency of accommodation due to age related changes in lens (decreased elasticity and increased hardness) and ciliary muscle power is the commonest form of accommodative dysfunction. [50] It will cause gradual decrease in near vision.