Effects Of Gaze Before And After Air-conducted Sound Stimulation On Ocular Vestibular Evoked Myogenic Potential (oVEMP) In Healthy Young Adults

The ocular vestibular evoked myogenic potential(oVEMP)is a short-latency myogenic response via air-conducted sound(ACS),bone-conducted vibration(BCV)or galvanic stimulation,which can be recorded by surface electrodes placed over the contralateral extraocular muscles.The oVEMP is mainly originated from the utricle and passes through the superior vestibular nerve to the contralateral inferior oblique muscle,reflecting predominantly otolith-ocular function,which is an effective method to detect the function of the utricle-superior vestibular nerve pathway.At present,the international standards for methods and parameter settings of the test for oVEMP have not been established.Scholars have studied oVEMP mainly from the following aspects:the type,phase and intensity of stimulus,body position,gaze angles,electrode positions,and so forth.In order to find out the appropriate gaze occasion for oVEMP and provide a basis for clinical work,this article will focus on the difference of oVEMP elicited by gaze before and after ACS stimulation in healthy young adults.Objectives:To investigate the difference of oVEMP elicited by gaze before and after ACS stimulation in healthy young adults and to select the appropriate gaze occasion for oVEMP.Methods:Fifteen healthy young adults(30 ears)were enrolled in this study.Two gaze methods were used,including gaze at the fixed target before and after ACS stimulation successively.The response rate,nI latency,pI latency,nI-pI interval,nI-pI amplitude,asymmetry ratio and the incidence rate of eye fatigue were recorded and compared between the two gaze methods.Results:The response rates of oVEMP were 100%(30/30)and 96.7%(29/30)respectively by gaze before and after ACS stimulation.No significant differences existed in terms of the response rates,nI and pI latencies,nI-pI interval,nI-pI amplitude and asymmetry ratio between the two gaze methods.The incidence rate of eye fatigue by gaze before ACS stimulation was greater than that by gaze after ACS stimulation(P<0.05).Conclusion:Although the length of gaze which was the time of extraocular muscles’contraction and eye movements did not affect oVEMP under the conditions of this experiment,the incidence rate of the subject’ eye fatigue increased with the extension of gazing time.Both the two methods of gaze before and after ACS stimulation can be used for oVEMP test.The method of gaze after ACS stimulation is recommended as the clinical preferred method,for its lower incidence rate of eye fatigue,subjects’ less discomfort and shorter test time.