To determine the effects of postural changes, the effect of gravity on eyelid and brown position was analyzed. Researchers collected 112 front-facing portraits from 18 astronauts while they were on earth and in space from the NASA image database. A digital measurement of margin reflex distance 1 (MRD1) and pupil to brow distance (PTB) were collected.
“Analysis of the data revealed that with respect to MRD1 there was essentially no change in the mean and standard deviation…when moving from earth to space,” said Justin Karlin, MD, MS during a presentation at ASOPRS 2020 Fall Scientific Symposium.
However, when comparing earth to space, PTB measurement showed a 3.4 mm rise, which was statistically significant.
Dr Karlin concluded that the brow is susceptible to gravity’s pull where the eyelid height is more tightly regulated.
“The brow is only activated secondarily for ocular protection and its main role is in facial expression,” he said. “On the other hand, the eyelid is critical for ocular protection and for this reason it would make sense that eyelid height would be more regulated more tightly than brow height”
Future studies could potentially explore whether the lateral brow elevates more than the medial brow.
Karlin J. The effect of zero gravity on eyelid and brow position. Presented at ASOPRS 2020 Fall Scientific Symposium.