L'effet de la distance sur le quotient de Romberg

Romberg's test usually shows a stabilizing effect with eyes open than with eyes closed. Romberg's quotient (RQ) is generally 2.5. We examined the role of the converging angle on the quotient. We measured postural stability using a posture graphic platform in 18 young adults (mean age 25.3) and 17 elderly patients (mean age 61.6). They were instructed to fix a target 40 to 200 cm away. The RQ was of 2 to 40 cm but dropped to 1 at 200 cm. In a second experience, 15 subjects (mean age 26.7) passed the same test but this time the conditions were light versus dark, 5 distances were tested (20, 40, 90, 200 and 350 cm) and the converging angle was measured with a video oculometer. The RQ at 20 and 40 cm was close to 2 and once again it dropped to 1 for the greater distances (90, 200 and 350 cm). In parallel, the converging angle between light and dark was significantly greater for the closer distances (20 and 40 cm) than for the greater distances (90, 200 and 350 cm). Thus, the RQ co-varies with the deviation of the converging angle between light and dark. Regarding the widely admitted idea according to which the RQ signals the benefit of sight, this study provides certain doubts on such an interpretation, at close distance the signals relative to the loss of the converging angle in the dark would be a source of instability.