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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.
Negative relative accommodation (NRA) was proposed by Joseph Kearney of Oxford University in 1967 as a measure of the maximum ability to relax accommodation while maintaining clear, single binocular vision.
Symptom assessment is a key component of dry eye diagnosis – to the extent that many believe dry eye syndrome to be a symptom-based disease. Several questionnaires have been developed to determine a score that would allow for a diagnosis. The McMonnies & Ho dry eye questionnaire is often used in clinical studies of dry eyes. [29]
Convergence insufficiency - usually associated with accommodative difficulties, the fusional convergence range of these patients is reduced. Divergence insufficiency- although rare and usually associated with a neurological condition, the PFR is able to detect a reduced divergence range.
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.
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.
Fusional amplitude and relative fusional amplitude training are designed to alleviate convergence insufficiency. The CITT study (Convergence Insufficiency Treatment Trial) was a randomized, double-blind multi-center trial (high level of reliability) indicating that orthoptic vision therapy is an effective method of treatment of convergence ...
Clinically, accommodative convergence is measured as a ratio of convergence, measured in prism diopters, to accommodation, measured in diopters of near demand. The patient is instructed to make a near target perfectly clear and their phoria is measured as the focusing demand on the eye is changed with lenses.