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Convergence insufficiency. 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.
Accommodative convergence is that portion of the range of inward rotation of both eyes (i.e., convergence) that occurs in response to an increase in optical power for focusing by the crystalline lens (i.e., accommodation).
Accommodative vergence is measured as the ratio between how much convergence takes place for a given accommodation (AC/A ratio, CA/C ratio). Proximal vergence is sometimes also called voluntary vergence , which however more generally means vergence under voluntary control and is sometimes considered a fifth type of vergence. [4]
Convergence insufficiency is characterized by one or more of the following diagnostic findings: patient symptoms, high exophoria at near, reduced accommodative convergence/accommodation ratio, receded near point of convergence, and low fusional vergence ranges and/or facility. Some patients with convergence insufficiency have concurrent ...
The accommodation reflex (or accommodation-convergence reflex) is a reflex action of the eye, in response to focusing on a near object, then looking at a distant object (and vice versa), comprising coordinated changes in vergence, lens shape (accommodation) and pupil size.
Accommodative insufficiency. Accommodative insufficiency is the condition where amplitude of accommodation of a person is lesser compared to physiological limits for their age. Premature sclerosis of lens or ciliary muscle weaknesses due to systemic or local cases may cause accommodative insufficiency.
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.
Vergence-accommodation conflict (VAC), also known as accommodation-vergence conflict, is a visual phenomenon that occurs when the brain receives mismatching cues between vergence and accommodation of the eye.
A spasm of accommodation (also known as a ciliary spasm, an accommodation, or accommodative spasm) is a condition in which the ciliary muscle of the eye remains in a constant state of contraction. Normal accommodation allows the eye to "accommodate" for near-vision.