The Effect of Zero Gravity on Eyelid and Brow Position

Head rotation and the perception of eyelid height and contour

PURPOSE

Effective visual perceptual processing is one of the many components of surgical competence. Human face identification is most efficient when viewed upright. However, it is not yet clear how this perception sensitivity impacts eyelid symmetry. This study investigates surgeons' and laypeople's accuracy and efficiency in perceiving eyelid asymmetry from different spatial perspectives.

METHODS

A prospective psychometric experiment was conducted where oculoplastic surgeons were recruited from the American Society of Ophthalmic Plastic and Reconstructive Surgery and the Brazilian Oculoplastic Surgery Society, and control participants were recruited via crowdsourcing (Amazon's Mechanical Turk). Standard illustrations of the human face with varying degrees of eyelid abnormality, laterality, gender and rotation were presented to participants who were asked to judge whether the eyelids were symmetric or asymmetric.

RESULTS

The survey was completed by 75 oculoplastic surgeons (49.33% male; mean age of 46.9±10.7) and 192 lay individuals (54.6% male; mean age 34.6±11.3 years). Among oculoplastic surgeons, deviation from upright was significantly associated with increased reaction time and decreased proportion correct (OR per 45° for peak 0.68, 95% CI 0.60 to 0.77, p<0.001; OR per 45° for ptosis 0.52, 95% CI 0.32 to 0.87, p=0.012; OR per 180° for aggregate responses 0.56, 95% CI 0.51 to 0.61, p<0.001). Oculoplastic surgeons demonstrated increasing accuracy and decreasing reaction time with additional trials for both peak and ptosis.

CONCLUSION

Oculoplastic surgeons perceive eyelid asymmetries more accurately and can better compensate for inverted sensory information. However, accuracy increases and reaction time decreases with additional trials, suggesting trainability and potential for improvement in inversion disability.

Dry eye disease in astronauts: a narrative review

Long-duration spaceflight can have adverse effects on human health. One of the most common ocular conditions experienced by astronauts is dry eye disease (DED). Symptoms of DED include feelings of eye irritation, eye strain, foreign body sensation and blurred vision. Over 30% of International Space Station expedition crew members reported irritation and foreign body sensation. We reviewed the current literature on the prevalence and mechanisms of DED in astronauts and its potential implications for long-duration spaceflight, including the influence of environmental factors, such as microgravity and fluid shift on tear film physiology in space. DED has negative effects on astronaut performance, which is why there is a need for further research into the pathophysiology and countermeasures. As an in-flight countermeasure, neurostimulation seems to be among the most promising options.