Eye Tracking Device (ETD) - 03.19.15
The Eye Tracking Device (ETD) will determine the influence of prolonged microgravity and the accompanying vestibular (inner ear) adaptation on the orientation of Listing's Plane (a coordinate framework, which is used to define the movement of the eyes in the head). Science Results for Everyone
Here’s looking at you, kid – or at least trying to. Researchers found that, while microgravity does not directly influence visual function, the changes it causes to the vestibular system – the inner ear and nerves that maintain our body’s balance and orientation –lead to a decrease in visual tracking ability. Similar disturbances in the accuracy of visual tracking and compensatory movements, seen in previous spaceflights, lead to an increase by a factor of three or more in the time it took astronauts to examine and identify a target. Complete recovery of eye tracking function was not observed at 9 days postflight but gradual restablization was noted. Experiment Details
Kayser Threde, Munich, Germany
Sponsoring Space Agency
European Space Agency (ESA)
ISS Expedition Duration
October 2003 - April 2008
Previous ISS Missions
Performed on ISS Expeditions 9, 10, 11. ^ back to top
- The Eye Tracking Device (ETD) investigation will determine how the vestibular (inner ear) system adapts to a weightless environment and how this relates to the occurrence of space sickness in manned space flights.
- This type of research can further provide an insight into vestibular disorders on Earth such as Meniere's disease (balance disorder of the inner ear) and related vestibular symptoms such as vertigo and nausea.
The working hypothesis is that in microgravity the orientation of Listing's Plane is altered, probably to a small and individually variable degree. Further, with the loss of the otolith-mediated gravitational reference, it is expected that changes in the orientation of the coordinate framework of the vestibular system occur, and thus a divergence between Listing's Plane and the vestibular coordinate frame should be observed. While earlier ground-based experiments indicate that Listing's Plane itself is to a small degree dependent on the pitch orientation to gravity, there is more compelling evidence of an alteration of the orientation of the vestibulo-ocular reflex (VOR), reflex eye movement that stabilizes images on the retina during head movement by producing an eye movement in the direction opposite to head movement, thus preserving the image on the center of the visual field, in microgravity.
Furthermore, changes in bodily function with relation to eye movement and spatial orientation that occur during prolonged disturbance of the vestibular system most likely play a major role in the problems with balance that astronauts experience following re-entry from space.
In view of the much larger living and working space in the ISS, and the extended program of spacewalks (EVAs) being planned, particular care must be given to assessing the reliability of functions related to eye movement and spatial orientation.
The performance of the experiments in space are therefore of interest for their expected contribution to basic research knowledge and to the improvement and assurance of human performance under weightless conditions.
Examination of the orientation of the Listing's plane during the course of a prolonged space mission is of particular interest, as on Earth the Listing's plane appears to be dependent on input from the vestibular system, i.e., detected through the head position with relation to gravity. By exposing the astronaut to the weightlessness of space, this experiment can follow the subsequent adaptation of the astronaut's vestibular system during the flight and after re-entry.
This study has important implications understanding basic mechanisms of motor control in microgravity and for rehabilitative training of neurological patients with impaired motor control.
The ETD consists of a headset that includes two digital camera modules for binocular recording of horizontal, vertical and rotational eye movements and sensors to measure head movement. The second ETD component is a laptop PC, which permits digital storage of all image sequences and data for subsequent laboratory analysis. Listing's Plane can be examined fairly simply, provided accurate three-dimensional eye-in-head measurements can be made. Identical experimental protocols will be performed during the pre-flight, in-flight and post-flight periods of the mission. Accurate three-dimensional eye-in-head measurements are essential to the success of this experiment. The required measurement specifications (less than 0.1 degrees spatial resolution, 200 Hz sampling frequency) are fulfilled by the Eye Tracking Device (ETD).
Using the ETD all of the subjects, both short-duration and long-duration, are examined:
- Pre-flight , on the ground, at L- 6 months (launch minus), then four times leading up to the launch typically at L-3 months (+/- 2 weeks), L-21 days (+/-2 days), L-14 days (+/-2 days) and L-7 days (+/-2 days). The total duration of each session is approximately 30 minutes total for each subject except the last one at L-7 days, which has a duration of 1 hour.
- In-flight , at 48-hour intervals for a maximum of 4 sessions (Flight Day 3, 5, 7 and 9). Each session lasts approximately 30 minutes.
- Post-flight , for readaptation on days R+0 (return plus), R+2, R+4, R+6, R+8, R+10 and R+12, and once again at approximately R+60.
Visual functions were observed in-flight for 31 astronauts under prolonged microgravity conditions. The precision and speedy parameters of all the forms of visual tracing such as fixational rotations of the eyes (saccades), smooth tracking of linear and curved movements of a focal point stimulus, and following a vertical pendulum-like movement stimuli became worse, and in a number of cases a complete disintegration of the smooth tracing reflex occurred as well as an increase in the time taken to fix the gaze on a target (by factors of 2 or more), and decreases in the frequency of stimulus tracking. During the initial period of adaptation to spaceflight and periodically during prolonged flight, the system of smooth visual tracking was found to undergo a transition to a strategy of saccadic approximation (abrupt rapid movements of both eyes). These impairments, seen in virtually all the crewmembers, are apparently due to vestibular deprivation in space. Pre- and postflight examinations of 9 cosmonauts participating in ISS missions 3-9 were performed using a computer-aided method to investigate eye motion control and vestibular function after long-term stay in microgravity (126–195 days). Studies of the vestibular function, intersensory interactions, and the tracking function of the eyes in the crew members were performed on days 1-2, 4-5 and 8-9 after return to Earth. The role and significance of the vestibular system (the vestibule and semicircular canals of the inner ear and the vestibulocochlear nerve which work with the brain to maintain balance and orientation) in eye tracking were determined. Results of the postflight examinations showed a significant change in the accuracy, velocity, and temporal characteristics of eye tracking and the muting of the vestibular response. Although, microgravity does not directly influence visual functions, changing the level and pattern of inner ear sensory/receptor input leads to a decrease in the accuracy and velocity of all forms of visual tracking. Eye destabilization related to an increase in slow drift, the appearance of a great number of saccadic (abrupt fast) movements, and the emergence of spontaneous nystagmus (involuntary eye movement) was found. Similar disturbances, as those previously seen during flight, in the accuracy of saccadic and smooth tracking (especially in the vertical plane) and the development of a new tracking strategy (the gaze approaches a target and follows its movement using a set of saccadic movements) were demonstrated and lead to a considerable increase (by a factor of three or more) in the time required for examining and identifying a target and setting the gaze on targets post landing. In the selected period of examination (nine days after the flight), no recovery of the indices of the tracking eye function to the baseline level was observed; however, a tendency for normalization was recorded.^ back to top
Clarke AH, Just K, Krzok W, Schonfeld U. Listing's plane and the 3D-VOR in microgravity--the role of the otolith afferences. Journal of Vestibular Research - Equilibrium & Orientation. 2013 January 1; 23(2): 61-70. DOI: 10.3233/VES-130476. PMID: 23788133.
Clarke AH. Listing's Plane and the 3D-VOR in microgravity. 2008 Life in Space for Life on Earth Symposium, Angers, France; 2008 June 22-27 2 pp. [Also: AH. Clarke, (2008) Listing’s Plane and the 3D VOR in microgravity. J Gravit. Physiol, , Vol 15:1, 29-30.]
Clarke AH, Kornilova LN. Ocular torsion response to active head-roll movement under one-g and zero-g conditions. Journal of Vestibular Research - Equilibrium & Orientation. 2007; 17(2-3): 99-111. PMID: 18413903.
Kornilova LN. The Role of Gravitation-dependent Systems in Visual Tracking. Neuroscience and Behavioral Physiology. 2004; 34(8): 773-781. DOI: 10.1023/B:NEAB.0000038127.59317.c7.
Kornilova LN, Alekhina MI, Temnikova VV, Reshke M, Sagalovich VN, Malakhov SV, Naumov IA, Kozlovskaya IB, Vasin AV. The Effect of a Long Stay Under Microgravity on the Vestibular Function and Tracking Eye Movements. Human Physiology. 2006; 32(5): 547-555. DOI: 10.1134/S0362119706050082. [Original Russian Text © L.N. Kornilova, M.I. Alekhina, V.V. Temnikova, M. Reshke, S.V. Sagalovich, S.V. Malakhov, I.A. Naumov, I.B. Kozlovskaya, A.V. Vasin, 2006, published in Fiziologiya Cheloveka, 2006, Vol. 32, No. 5, pp. 56–64.]
Clarke AH. Listing's plane and the otolith-mediated gravity vector. Berlin: Progress in Brain Research (2008); 2008.
Ground Based Results Publications
Clarke AH, Haslwanter T. The orientation of Listing’s Plane in microgravity. Vision Research. 2007 November; 47(25): 3132-3140. DOI: 10.1016/j.visres.2007.09.001.
Clarke AH. Vestibulo-oculomotor research & measurement technology for the space station era. Brain Research Reviews. 1998 Nov; 28(1-2): 173-184. PMID: 9795204.
Bockisch CJ, Haslwanter T. Three-dimensional eye position during static roll and pitch in humans. Vision Research. 2001; 41(16): 2127-2137.
Columbus Mission - European Experiment Programme
The information provided is courtesy of the ESA Astrolab Mission web page.
NASA Image: ISS011E13710 - Cosmonaut Sergei K. Krikalev, Expedition 11 Commander representing Russia's Federal Space Agency, uses the Eye Tracking Device (ETD), a European Space Agency (ESA) payload in the Zvezda Service Module of the International Space Station. The ETD measures eye and head movements in space with great accuracy and precision.
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