The Effect of Zero Gravity on Eyelid and Brow Position. 2021

Justin N Karlin, and Justin Farajzadeh, and Stephanie Stacy, and Mahtash Esfandiari, and Daniel B Rootman
Division of Orbital and Ophthalmic Plastic Surgery, Doheny and Stein Eye Institutes, University of California.

To describe the effect of spaceflight on upper eyelid and brow position. Images of astronauts on earth and in space were collected from a National Aeronautics and Space Administration image library. For each astronaut, front facing portraits captured within a 5-year period were obtained. 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 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. Linear-mixed effects modeling, analysis of variance and post hoc power analysis were performed. One hundred and twelve photographs (55 earth, 57 space) from 18 astronauts (4 women, 14 men; mean age 45.9 years) were retrieved. Zero gravity resulted in a mean PTB increase of 3.7 mm (p < 0.01) but did not result in significant change in MRD1 (p = 0.21). 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, we can be 97.4% confident that a difference in MRD of 0.5 mm or greater would be detected. While spaceflight led to significant elevation of PTB, it did not consistently alter MRD1. As such, the brow and eyelid appear to be independently regulated with respect to gravitational changes.

UI MeSH Term Description Entries
D008297 Male Males
D008875 Middle Aged An adult aged 45 - 64 years. Middle Age
D011680 Pupil The aperture in the iris through which light passes. Pupils
D001763 Blepharoptosis Drooping of the upper lid due to deficient development or paralysis of the levator palpebrae muscle. Ptosis, Eyelid,Blepharoptoses,Eyelid Ptoses,Eyelid Ptosis,Ptoses, Eyelid
D005138 Eyebrows Curved rows of HAIR located on the upper edges of the eye sockets. Eyebrow
D005143 Eyelids Each of the upper and lower folds of SKIN which cover the EYE when closed. Eyelid
D005260 Female Females
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D014893 Weightlessness Condition in which no acceleration, whether due to gravity or any other force, can be detected by an observer within a system. It also means the absence of weight or the absence of the force of gravity acting on a body. Microgravity, gravitational force between 0 and 10 -6 g, is included here. (From NASA Thesaurus, 1988) Microgravity,Zero Gravity,Gravity, Zero

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