The role of retinotopic cues in deciphering the direction and magnitude of monocular dynamic ocular accommodation: A review.

Accommodative responses of humans operate seamlessly to ensure clear vision of targets at different viewing distances, up until the onset of presbyopia. To achieve this, the visual system must correctly decipher the polarity and magnitude of retinal defocus in real-time, and often under very challenging viewing conditions. The past seven decades of research in this area has identified several retinotopic cues that may potentially provide the desired odd- and even-error information to the visual system for solving these challenges. These studies have used a variety of technology, experimental paradigms and outcome measures to determine the putative contribution of a given cue, or set of cues, in solving this problem. A variety of results, some offering consensus and others conflicting, have been observed in these studies. The present review distils this large volume of literature into specific, take-away points for the early reader of this topic, acknowledging that the problem is non-trivial and far from being solved. The review also reveals that many of these studies may not have used appropriate/sensitive methodology or outcome measures to tease apart the relative contribution of a cue in solving the direction and magnitude challenge. The review concludes with the proposal that, since a multitude of cues may be used by the visual system for solving these problems, future studies could employ a Bayesian statistical cue-combination approach to address this problem. Such approaches have yielded very meaningful insights in other areas of human decision-making involving multiple inter- and intra-modal combination of cues.