Abstract
To clearly view approaching objects, the eyes rotate inward (vergence), and the intraocular lenses focus (accommodation). Current ocular control models assume both eyes are driven by unitary vergence and unitary accommodation commands that causally interact. The models typically describe discrete gaze shifts to non-accommodative targets performed under laboratory conditions. We probe these unitary signals using a physical stimulus moving in depth on the midline while recording vergence and accommodation simultaneously from both eyes in normal observers. Using monocular viewing, retinal disparity is removed, leaving only monocular cues for interpreting the object’s motion in depth. The viewing eye always followed the target’s motion. However, the occluded eye did not follow the target, and surprisingly, rotated out of phase with it. In contrast, accommodation in both eyes was synchronized with the target under monocular viewing. The results challenge existing unitary vergence command theories, and causal accommodation-vergence linkage.
Highlights
To clearly view approaching objects, the eyes rotate inward, and the intraocular lenses focus
Strabismus is often accompanied by amblyopia, manifest as poor acuity in the misaligned e ye[31,32,33,34]
A previous s tudy[59] investigated smooth pursuit of target motion in depth in monkeys. While these researchers found evidence of asymmetric vergence during binocular viewing in support of independent control, target motion in their study was usually aligned with one eye, where asymmetric vergence is expected
Summary
To clearly view approaching objects, the eyes rotate inward (vergence), and the intraocular lenses focus (accommodation). The models posit that all eye movements are a response to retinal signals, but that vergence is driven by monocular depth cues and, critically, by a unitary accommodation signal that focuses the intraocular lens to clearly view objects in d epth[24,25,26,27]. Some studies measured behavior of the viewing eye with one eye occluded, but within dichoptic viewing paradigms[27,44,45] This method usually eliminates monocular depth cues that are ubiquitous in natural environments and drive accommodation and v ergence[46,47,48,49,50,51,52]. While these researchers found evidence of asymmetric vergence during binocular viewing in support of independent control, target motion in their study was usually aligned with one eye, where asymmetric vergence is expected
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