The part of the range of convergence, i.e., inward rotation of both eyes that arises in response to a change in optical focusing power by accommodation. When the eyes engage the system of accommodation to focus on a near target, a signal is automatically transmitted to the extraocular muscles responsible for inward eye movement. It helps to maintain a single, comfortable and clear vision during near tasks, such as reading. AC is measured as a ratio of convergence, expressed in prism diopters, to accommodation, expressed in near demand diopters.
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