Role of optic flow on postural control in subjects with retinopathy

Abstract

Purpose : During our daily life we are continuously exposed to optic flow patterns which provide crucial information about self-motion and environmental structures. The aim of this study was to assess how optic flow processing contributes to the control of posture and if it requires the predominant activation of cortical networks involved in motion perception or the intervention of subcortical loops.

Methods : To this purpose, we recruited 34 volunteers with different retinal functionality: 13 people at early stage of retinopathy (retinopathy group, average age 62), 8 people who underwent a laser treatment on the peripheral retina (laser group, average age 62) and 13 healthy subjects (control group, average age 59).
Subjects looked at a tangent screen, covering 135 x 107° of visual field, on which radial optic flow fields were presented: full field, in the foveal or in the peripheral regions. The spatial distribution of dot speed was manipulated to simulate specific heading directions. Postural responses were recorded using surface electromyography (EMG) and stabilometry during visual stimulation. EMG data were recorded bilaterally from the anterior tibialis and soleus, while subjects stood on two Kirstel force platforms. We analyzed four center of pressure (COP) parameters: antero-posterior (AP), medio-lateral (ML), speed and area. Fixation in the dark was used as baseline.
A repeated measures ANOVA was performed on the normalized EMG and COP parameters, with side (right–left) as within-subjects and group and stimuli as between-subjects.

Results : We found significant differences between groups in all COP variables (p<0.001). A main effect of side and an interaction effect of group x side were found for COP_ML (p<0.001), COP_Area (p=0.010) and COP_Speed (p<0.001). The EMG analysis showed a significant main effect for group (p<0.001). Post-hoc test showed a significant difference between control and retinopathy (p<0.001) and laser and retinopathy (p=0.002).
People with retinopathy and people who underwent a laser treatment showed a higher postural instability than controls.

Conclusions : Based on these findings, the postural control seems to be a process dependent to the perceptual analysis via cortical networks involved in motion perception.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.