THE OTOLITHIC-OCULAR REFLEX AND VISUAL SENSATIONS DURING VERTICAL ACCELERATION

Background: We investigated the effect of vertical acceleration upon t he otolithic-ocular reflex of 22 healthy people. The study was perform ed to obtain standard Values for subsequent investigations at patients . Methods: People sitting on a chair were accelerated in the vertical axis with an amplitude of 4 cm and the frequencies of 0.5 Hz, 1 Hz, 1. 5 Hz, 2 Hz, 2.5 Hz and 2.7 Hz. The movements of the ocular globe were initially recorded during vertical acceleration with the eyes closed. Then visual acuity was tested during linear acceleration with the eyes open. As parameters of evaluation we used coherence and alteration of the Visual acuity. Results: When the frequency was increased while th e eyes were closed, coherence increased and the number of people with vertical eye movements increased. Amplitude was observed to increase a nd a phase shift occurred. A significant value of cohrence (> 0.8) was observed at a frequency above 2.5 Hz. During the test of visual acuit y, coherence also increased but did not reach quantity we observed ini tially. A significant loss of visual acuity occurred at a frequency ab ove 2.5 Hz. A phase shift was also observed. The reason for the loss o f visual acuity was the increment of amplitude and the phase shift, wh ich had a negative influence on fixation. Conclusions: In summary, rea ctions with closed eyes are best tested at frequencies of 2.5 and 2.7 Hz. We recommend frequencies of 1.5 and 2 Hz for testing visual acuity .