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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.
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. [5]
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.
Vision therapy is a broad concept that encompasses a wide range of treatment types. [3] These include those aimed at convergence insufficiency – where it is often termed "vergence therapy" or "orthoptic therapy" – and at a variety of neurological, educational and spatial difficulties. [3]
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 ]
Near (1/3m): 15Δ BI → 35-40Δ BO; Distance (6m): 5-7Δ BI → 15Δ BO; Vertical: 3Δ BU → 3Δ BD; If patient results do not reflect the normal values, they may have the following issues: Convergence insufficiency - usually associated with accommodative difficulties, the fusional convergence range of these patients is reduced.
Vision assessment and cycloplegic refraction should be done. If there is any refractive errors, it should be corrected before considering orthoptic treatments.The accommodative infacility is commonly treated with vision therapy/orthoptics; one study found that 12 weeks of treatment had a significant effect on visual accommodation.
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.