左右逆転プリズムの身体動揺に対する影響について : 重心動揺計による定量的検討

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The visual sensation plays on an important role for the maintenance of upright standing posture in addition to labyrinthine and proprioceptive sensation. In general, visual-vestibular interaction keeps standing posture stable, but on the contrary, optical reversal, as one form of visual stimuli, causes it to become unstable because the gain control system of vestibulo-ocular reflex is disturbed. The purpose of this paper is to study the effect of optical reversal. on the standing posture of normal subjects by measuring motion of the center of gravity and to discuss the possibility of using optical reversal as a clinical tool for detecting vestibular disorders.The subjects were 16 normal young adults (24 to 30 years of age). Three different visual conditions for stimuli were used i. e. with eyes open, with eyes closed and with the optical reversal. Horizontal vision reversing prisms (RP) with visual angles of 60 degrees was used for the optical reversal. The center of gravity was analyzed in Romberg and Mann positions. The total shifting length (TSL) of the center of gravity for 40 seconds was measured and analyzed by a computerized system. Recordings of eye head coordination of a normal subject without and with reversing prisms were performed for the study of ocular dysmetria.Results were as follows: 1) In Romberg position, the TSL with optical reversal was significantly longer than with eyes open (P<0.01) but not different from with eyes closed. 2) In Mann position, the TSL with optical reversal was longer than with eyes closed (P<0.01) and still more with eyes open (P<0.001). 3) The adaptive effect of optical reversal in six subjects during an hour was studied every 10 minutes in Romberg and Mann position, but the TSL did not change during that limited time. 4) Head movement with reversing prisms was just the opposite direction to normal. Reversing prisms created vestibulo-ocular dysmetria.Our data suggest reversing prisms could give two kinds of opposite effects for standing postures. The one which was demonstrated in Romberg position is to maintain standing posture stable as well as usual sensation. The other effect which was demonstrated in Mann position is to cause standing posture to become unstable because the reversing prisms creates vestibuloocular dysmetria. Since these two effects compete together for postural control, reversing prisms would have a possibility for a clinical tool as screening test of vestibular disorders.
社団法人日本耳鼻咽喉科学会の論文

左右逆転プリズムの身体動揺に対する影響について : 重心動揺計による定量的検討

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