Ocular Accommodation: The Autofocus Mechanism of the Human Eye.

Ocular accommodation, the autofocus mechanism of the human eye, is fundamental for the achievement and maintenance of clear vision across viewing distances. Together with its close ally, vergence eye movements, this mechanism also ensures that binocular single vision is achieved at all these distances. Several dimensions of this mechanism have been investigated for well over a century. The present article summarizes this large volume of work under three themes: (a) biomechanics and neural control of the accommodative apparatus, (b) its behavioral properties, and (c) control-engineering modeling endeavors that offer a theoretical framework for gaining insights into the functioning of this mechanism. Built into these themes is a discussion on the development of accommodation, its loss with aging (presbyopia), sensory cues that aid the generation of these responses, and the technologies available for the measurement of these responses. The article also raises several unresolved questions for future research.