Short-term Structural and Microvascular Ocular Changes Induced by Hypergravity Exposure During Human Centrifuge Training.

Purpose: To analyze the short-term effects of hypergravity on ocular parameters, particularly retinal and peripapillary microvasculature changes, in participants undergoing human centrifuge training.

Methods: This prospective, observational study enrolled healthy trainees who participated in centrifuge training at the National Army GangShan Aviation Training Center, Kaohsiung City, Taiwan, from August to September 2023. Ocular data were collected at four time points: 24 hours before training, immediately after, and 15 and 30 minutes after exposure to gravitational force along the head-to-foot axis. Assessments included non-contact tonometry, optical biometry, and optical coherence tomography angiography. Nonparametric statistical methods were used for data analysis.

Results: Nineteen participants (12 male, seven female) with a mean age of 27.89 ± 4.4 years were included. Intraocular pressure, corneal curvature, and pupil diameter remained unchanged after centrifugation. However, axial length decreased immediately after centrifugation (25.79 ± 1.54 mm vs. 25.77 ± 1.57 mm; P = 0.012), then rebounded at 15 minutes (25.81 ± 1.53 mm) and 30 minutes (25.81 ± 1.54 mm; both P = 0.005). Central corneal thickness increased and remained elevated for 30 minutes. Retinal and peripapillary retinal nerve fiber layer thicknesses significantly increased after training (P < 0.05). Meanwhile, the parafoveal and perifoveal vessel density of the right eye showed a decreasing trend immediately after hypergravity exposure, followed by a rebound, although the change was not statistically significant.

Conclusions: Short-term exposure to hypergravity induces transient yet measurable alterations in ocular parameters, particularly retinal thickness and vascular density. These novel findings suggest potential mechanisms underlying hypergravity-associated visual impairment and highlight the importance of monitoring ocular health in individuals exposed to high-G environments.