The Plasticity of Compensatory eye Movements in Rotatory Tests: 1.The effect of alertness and eye closure

Abstract

Fifteen voluntary subjects with a mean age of 26 years (17-39), participated in two rotatory experiments. The rotatory test used was sinusoidal harmonic acceleration (SHA) test at frequencies of 0.01-0.32 Hz. Compensatory eye movements were measured by means of EOG. Experiment A included rotation in darkness during alerting tasks (day 1), rotation in darkness with no tasks (day 2) and rotation in darkness during alerting tasks (day 3). In the alertness tests, the gain varied between 0.5 and 0.77. Phase values decreased with increasing frequency. The alertness results between days 1 and 3 did not differ in gain or phase. The gain of day 2 (no tasks) displayed significantly reduced gain at all frequencies, and a more pronounced decrease in phase than in the alertness tests. Experiment B comprised testing with eyes open (day 1) and eyes closed (day 2) during alerting tasks. These tests displayed significantly decreased gain at all frequencies with eyes closed compared with eyes open and with more negative phase at 0.08-0.32 Hz with eyes closed. The results indicate a central effect of the alertness level on compensatory eye movements, and the effect of eye closure might be explained by bio-mechanical and possibly even central effects on the eye movements. In low-frequency testing, as short a test time as possible should be used, and due to different alertness levels, the results should be evaluated with great caution.

Normative data for ages 18‐45 for ocular motor and vestibular testing using eye tracking

“…For example, Peterka et al 57 report VOR gain, phase, and asymmetry at 0.05, 0.2, and 0.8 Hz (216 subjects ages 7‐81), Maes et al 31 report gain, phase, and asymmetry at 0.01‐0.16 Hz (150 subjects ages 18‐40), Chan et al 30 present VOR gain at 0.01‐0.64 Hz (100 subjects ages 6‐78, reported by age groups 6‐12, 13‐17, 18‐30, 31‐50, and >50. 30 Other papers report data from smaller cohorts, including Wall 58 (50 subjects ages 20‐59; 0.005‐1.0 Hz), Moller 59 (50 subjects ages 17‐39; 0.01‐0.32 Hz), Li 13 (41 subjects ages 21‐67, 0.01‐0.64 Hz). Collectively, these studies reflect the importance of this test and need for normative data.…”

Bilateral Vestibular Hypofunction: Challenges in Establishing the Diagnosis in Adults

“…This could result in a false-positive diagnosis of vestibular hypofunction. Many vestibular laboratories prefer to have the eyes of the patient open during testing, since closing the eyes decreases gain of the vestibulo-ocular reflex [132]. For the VST, it is preferred to use the first rotation for familiarization with the test to get responses as accurate as possible [131].…”

Influence of Head Position on the Vestibulo-ocular Reflex During Rotational Testing

“…Also the situation of eye closure is known to influence the intensity of nystagmus (12). Moller et al (13) established a significant decrease of gain during rotation at all frequencies with eyes closed compared with eyes open in the dark. In contrast, instructing the patient to maintain alertness by giving them arithmetic tasks during rotation increases the gain of the VOR.…”