The Oculomotor Systems Ability to Adapt to Structural Changes Caused by the Process of Senescence: A Review

Abstract

Age-related binocular vision anomalies are frequently encountered during clinical examination of mature patients. Observations of both concomitant and incomitant restrictions in eye motility indicate that all oculomotor system levels are implicated, from cortical neurons down to extraocular muscles. The system can make adaptations in response to changes induced by growth and ageing, which it does by monitoring and adjusting its own performance. This adaptive mechanism, which is important for maintaining motility, spatial orientation, and perceptual stability, seems to rely on extra-retinal information about eye position in relation to the head and trunk. Receptors in the extraocular muscles and the vestibular system, assumed to contribute to this type of information, also undergo age-related changes. This may compromise their ability to assist in the adaptive process and in potential calibrations of other neural systems. Furthermore, recent observations of a dual, common, final pathway and double insertions of distal extraocular muscles suggest that muscle and tendon receptors may facilitate other, still unresolved, functions in the visual system. Consequently, age-related changes in certain mechanoreceptors may have more severe implications for ocular motility and visual functions than previously assumed.This review aims to detail some of the most frequent neurogenic and myogenic age-related changes that take place in the human oculomotor system and relevant pre-motor structures. It will also address clinical implications of these changes and the potential adaptive mechanism they initiate.

Neuroanatomical Structures in Human Extraocular Muscles and Their Potential Implication in the Development of Oculomotor Disorders

“…[49][50][51] In humans, they have been observed at both the proximal and distal muscle insertions of infants and mature individuals. 52 It was reported that this tendon nerve ending in extraocular muscles is composed of myelinated nerve fibers that penetrate the tendon and then turn back 180 degrees to divide into several approximately parallel running branches exclusively on the tip of multiply innervated muscle fibers. 49 Greater numbers of myotendinous cylinders are found within the horizontal rectus muscle when compared with the vertical rectus or oblique muscles.…”

Visual and psychological stress during computer work in healthy, young females—physiological responses

“…They stated that this interaction between the eyes and the neck/shoulder muscle may be a neural command between sustained eye-lens accommodation when fixating on a near target and the postural muscles in the neck and shoulder area, which is activated to stabilize gaze during visually demanding conditions, such as near-visual work. In line with this, proprioceptive information from the oculomotor muscles and from somatic neck muscles has been shown to be mutually influential (Biguer et al 1982 ; Bruenech et al 2012 ; Han and Lennerstrand 1995 , 1998 ). The eyes and the head are activated synchronously with eye movements when looking at a visual target (Biguer et al 1982 ), and proprioceptive signals (vibration) of different neck muscles induce eye movements (Han and Lennerstrand 1995 ).…”

Neuroanatomical Structures in Extraocular Muscles and Their Potential Implication in the Management of Strabismus

“…This indicates that the oculomotor system can make muscle-force increments by activating one single muscle fiber at the time. This outranks all other somatic muscles in terms of motor control [15].…”