Does the perception of gravitational orientation, variations in the subject's position, influence binocular fusion?

Introduction: To perceive the environment, the brain jointly processes a multitude of sensory information provide by sensory modalities (auditory, visual, interoceptive, proprioceptive) and the subject's position in relation to gravitational orientation. Gravitational orientation influences sensory processing (standing compare lying position) and motor control (benefit or against gravity). Influence of gravitational orientation on binocular fusion (cortical mechanisms, role of ocular proprioception, corollary discharge, motor synchronisation of both eyes) was assessed by Perceptive Maddox, which revealed Labile Vertical Heterophoria (LVH), very small variations of the vertical angular deviation and expose the stability of both eyes when retinal fusion.Method: The lability index (LI) of 62 subjects with LVH (hard/crispondiabetes®/black pyramids®) was calculated between the following conditions: lying, sitting, standing, with the axis of gravity perpendicular (lying) and parallel (sitting/standing) to the subject.Results: LI scores: standing/lying: 49; seating/lying: 53; sitting/standing: 47 (Fischer exact p<0.000). No effects of genre and age were reported.Discussion/conclusion: Perception of gravitational orientation results in LVH lability equivalent. The lying position (perpendicular of the gravity) induced the seam variation that in sitting and standing (parallel of the gravity)). LVH, instability of visual spatial reference, reflecting a difficulty in integrating sensory information (difficulty/incapacity of the central nervous system to process adequately the flow of sensory information arriving in the brain in order to respond correctly to the demands of the environment), would be independent of gravitational orientation. The Perceptive Maddox can only complement the various clinical tests and confirm or invalidate the therapeutic proposal in multidisciplinary care.