Does Stimulation of Plantar Mechanoreceptors Alter Visual Spatial Localization?

Area of Science:

• Ophthalmology
• Biomechanics
• Neuroscience

Background:

• Postural control involves complex interactions between visual and somatosensory systems.
• The relationship between foot sole mechanoreceptors and vertical heterophoria (VH) is not well understood.
• Existing methods for assessing minimum VH are limited, especially for values below 1/2 prism diopter (pD).

Purpose of the Study:

• To investigate how stimulating foot sole mechanoreceptors affects VH.
• To introduce a novel, rapid method for assessing minimum VH.
• To explore the interrelation between the foot and gaze systems in postural control.

Main Methods:

• Assessed VH using the Maddox rod test with a new circular box device for precise measurement.
• Evaluated VH in 95 adults in an upright posture under various plantar stimulations (pins, foam).
• Measured minimum VH, particularly for values less than 1/2 pD.

Main Results:

• Nearly half of subjects had minimum heterophoria (VH < 1 pD), with 96% having VH ≤ 1/2 pD.
• Plantar stimulation (pins or foam) altered VH, shifting orthophoric subjects to heterophoric and vice versa.
• The new device facilitated rapid assessment of even the smallest heterophorias.

Conclusions:

• Plantar mechanoreceptor stimulation significantly influences VH, highlighting the foot-gaze interaction in posture.
• The novel device offers a fast and easy method for assessing subtle VH and the impact of postural interventions.
• Clinicians may benefit from this device for evaluating postural changes, though further validation is needed.