Gravity affects brow, eyelid position
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Gravity has a more pronounced effect on brow position than it does eyelid position, according to a presentation at the virtual American Society of Ophthalmic Plastic and Reconstructive Surgery annual meeting.
“Spaceflight affects the eyelid and brow differently,” Justin Karlin, MD, MS, said. “While the brow elevates consistently, the eyelid may elevate, fall or stay the same height.”
Karlin and colleagues collected at least six front-facing portraits of 18 astronauts from the NASA image database and digitally measured the margin reflex and pupil-to-brow distances. Portraits included three from Earth and three from space captured within a 5-year period for each individual. The mean age of the astronauts at photograph capture was 45.9 years.
The margin reflex distance showed a 0.15 mm fall when moving from Earth to space, while pupil-to-brow measurement displayed a 3.4 mm rise (P < .01), Karlin said.
“This highlights the differing roles of the brow and eyelid,” Karlin said. “The brow is only activated secondarily for ocular protection, and its main role is facial expression. On the other hand, the eyelid is critical for ocular protection, and for this reason, it would make sense that eyelid height would be regulated more tightly than brow height.”
Future studies should use contour measurements to investigate the difference between lateral brow and medial brow elevation and whether cephalad fluid shifts common in space travel contribute to the brow shifts, Karlin said.
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Karlin J, et al. The effect of zero gravity on eyelid and brow position. Presented at: American Society of Ophthalmic Plastic and Reconstructive Surgery annual meeting; Nov. 20-22, 2020 (virtual meeting).
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