Human accommodative visuomotor function is driven by contrast through ON and OFF pathways and is enhanced in myopia

The human eyes are continuously adjusting refractive power, vergence angle, and pupil diameter when exploring the visual environment. Adjustment errors in these visuomotor functions reduce the stimulus contrast driving ON and OFF retinal pathways, and ON retinal pathways become weaker, slower, and less sensitive in refractive disorders such as myopia. Here, we demonstrate that, in addition to these sensory deficits, myopes also have deficits in visuomotor functions driven by ON and OFF pathways during lens accommodation. We show that humans with myopia have excessive accommodative eye vergence with reduced ON pathway dominance and excessive accommodative pupil constriction. The excessive accommodative pupil constriction that we demonstrate could potentially weaken ON pathway responses and cause ON pathway deficits. This mechanism could explain why myopia increases with activities that maximize accommodative pupil constriction, such as near work, and decreases with activities/treatments that reduce it, such as outdoor activity, atropine, positive defocus, and low contrast. VIDEO ABSTRACT.