Spaceflight Results in Brow Elevation Without Consistent Eyelid Changes

Los Angeles, CA: A recent study revealed that spaceflight, although it does not consistently alter upper eyelid position, leads to a significant elevation of brow position. In simpler words, gravity has a more pronounced effect on brow position than it does on eyelid position. The study appears in the journal Ophthalmic Plastic and Reconstructive Surgery.

Study Overview

In the study, Justin Karlin, University of California, Los Angeles, CA, and colleagues aimed to describe the effect of spaceflight on upper eyelid and brow position.

For this purpose, the researchers collected images of astronauts on Earth and in space from a National Aeronautics and Space Administration image library. The researchers obtained front-facing portraits captured within a 5-year period for each astronaut. At least 6 photos were collected per astronaut, 3 taken on Earth, and 3 in zero gravity.

Measurements from the center of the pupil to the upper eyelid margin (MRD1) and the center of the pupil to the inferior eyebrow margin [pupil-to-brow (PTB)] were performed digitally for each image and averaged for each condition and each individual. Differences in mean MRD1 and PTB were assessed to illustrate the effects of zero gravity on eyelid and eyebrow position respectively.

Results

The researchers in total retrieved one hundred and twelve photographs (55 Earth, 57 space) from 18 astronauts (4 women, 14 men; mean age 45.9 years).

• Zero gravity resulted in a mean PTB increase of 3.7 mm but did not result in a significant change in MRD1.
• Post hoc power analysis of the measured MRD1 difference was performed by simulation.
• At an MRD1 difference of 0.5 mm, the probability of a type II error is 2.6%, equivalent to a beta power of 97.4%. Thus, the researchers were 97.4% confident that a difference in MRD of 0.5 mm or greater would be detected.

"While spaceflight led to a significant elevation of PTB, it did not consistently alter MRD1," wrote the authors. "As such, the brow and eyelid appear to be independently regulated with respect to gravitational changes."

Reference

Karlin, Justin N. M.D., M.S.*; Farajzadeh, Justin M.S.†; Stacy, Stephanie C.Phil.‡; Esfandiari, Mahtash Ph.D.‡; Rootman, Daniel B. M.D., M.S.* The Effect of Zero Gravity on Eyelid and Brow Position, Ophthalmic Plastic and Reconstructive Surgery: November/December 2021 - Volume 37 - Issue 6 - p 592-594 doi: 10.1097/IOP.0000000000001961