The Importance of the Interaction Between Ocular Motor Function and Vision During Human Infancy

Abstract

Numerous studies have demonstrated the impact of imposed abnormal visual experience on the postnatal development of the visual system. These studies have provided fundamental insights into the mechanisms underlying neuroplasticity and its role in clinical care. However, the ocular motor responses of postnatal human infants largely define their visual experience in dynamic three-dimensional environments. Thus, the immature visual system needs to control its own visual experience. This review explores the interaction between the developing motor and sensory/perceptual visual systems, together with its importance in both typical development and the development of forms of strabismus and amblyopia.

Keywords: accommodation; amblyopia; hyperopia; strabismus; vergence; visual development.

Figure 1

An illustration of the accommodation and vergence motor demands of the developing human visual system and the ways in which infants control their own postnatal visual experience. (a) Compared with adults, infants are typically more hyperopic. By increasing the optical power of their eyes via accommodation, they can move an image forward into focus on the retina. (b) Compared with adults, infants also have a narrower interpupillary distance and therefore need to rotate their eyes through a smaller angle to align both eyes at a target.

Figure 2

Individual trials collected from eight participants viewing a cartoon movie on a screen moving back and forth around a viewing distance of 50 cm on a motorized track (Seemiller et al. 2016). Uncalibrated vergence and accommodation responses were collected simultaneously at 50 Hz (PowerRef 3, Plusoptix). Data are smoothed over a 1-s window, and stimulus profiles are provided at the bottom of each panel for comparison. Abbreviations: D, diopter; MA, meter angle.

Figure 3

The role of fusional vergence in maintaining binocular eye alignment during typical development. The two graphs show alignment error as a function of hyperopic refractive error of individual participants aged (top) 3–5 months and (bottom) 2.5–5 years. The alignment error in pd is plotted for a target at an 80-cm viewing distance (1 pd is approximately 0.57°). Black circles indicate latent alignment error revealed when one eye was occluded (heterophoria), as shown in the center-left illustration. These participants typically have a small adult-like exophoria (divergent alignment error). Orange triangles indicate the maximum amount of convergent prism demand that was overcome to maintain reflex alignment in binocular conditions, as shown in the top-left illustration. Purple squares indicate the maximum amount of divergent prism demand that was overcome to maintain reflex alignment in binocular conditions, as shown in the bottom-left illustration. The distance between the triangles and squares indicates the range of errors the participant overcame to achieve alignment. Positive errors indicate convergent error, whereas negative errors indicate divergent error. U symbol indicates participants whose refractive errors were unknown (Sreenivasan et al. 2016). Abbreviations: BI, base in prism; BO, base out prism; D, diopter; pd, prism diopter.