Abstract
Purpose :
The impact of infantile nystagmus (IN) on postural control is poorly understood. IN is often associated with other visual diseases, such as albinism leading to poor stereovision and foveal hypoplasia reducing the quality of central vision. We investigated the role of central binocular and peripheral monocular visual fields for postural responses in IN compared to controls. To explore the contribution of vision relative to other sensory inputs we used: (1) a sway-referenced (SR) platform to reduce somatosensory inputs, and (2) the phenomenon of vection to motion.
Methods :
Postural responses in the anterior-posterior (A-P) plane were recorded using an Equitest system (Neurocom) in 20 participants with IN (unassociated: n=9; albinism: n=11) and 15 age-matched controls under the following conditions: (1) eyes closed compared to static visual stimuli in the central or peripheral fields under both fixed and SR platform conditions; (2) simulated 3D sinusoidal visual motion (0.05-4Hz) in the A-P plane in the central and peripheral visual fields to generate frequency response functions (static platform only). Responses were quantified using spectral analysis of sway in the A-P plane.
Results :
For the fixed platform condition, no significant differences in postural responses were observed between eyes closed compared to static visual stimuli in the central or peripheral fields for all participant groups. However, for the SR platform condition, the presence of either central or peripheral field static visual stimuli dramatically reduced postural sway compared to the eyes closed condition in the control group (p<0.001). In contrast, in the IN group, central static visual stimuli moderately reduced postural sway compared to eyes closed, with peripheral stimuli making less difference. Frequency response functions were similar for simulated central and peripheral motion in controls. In contrast, in participants with IN (albinism and unassociated), motion in the peripheral visual field led to a distinct peak of instability at 0.5Hz but not for motion in the central visual field.
Conclusions :
Individuals with IN rely less on vision in general for postural control compared to controls, particularly on peripheral visual information. They also have a propensity to experiencing vection for sinusoidal motion at 0.5Hz in the peripheral visual field leading to postural instability which might have functional implications.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.