To evaluate changes in intraocular pressure (IOP), central corneal thickness (CCT) and corneal biomechanics before and after exposure to hypobaric hypoxia, accounting also for Time of Useful Consciousness (TUC) as a parameter of short time exposure to systemic hypoxia.
Methods
This prospective, observational study recruited 45 healthy individuals training in Hypobaric Chamber. IOP, CCT and corneal biomechanics were evaluated before and immediately after the end using the Corvis ST. Comparisons of score values before and after hypoxia were performed with paired t-test for normally distributed differences. Difference between the IOP measurements was correlated with differences in CCT, corneal biomechanics and TUC with multivariate mixed effect linear regression models.
Results
Biomechanically corrected IOP (bIOP-Corvis) and pneumotonometry IOP as produced by Corvis ST (NCT) showed statistically significant higher values before hypoxia (p = 0.048 and p = 0.047 respectively). We observed a strong negative correlation of the difference between bIOP-Corvis before and after hypoxia with the difference in Deformation amplitude ratio (DARatio) (p < 0.001) and a significant positive correlation with the difference in Integrated Inverse Radius(IntegrRadius) (p = 0.01), Stiffness parameter at the first applanation (SPA1) (p < 0.001) and TUC (p = 0.023). We observed a strong negative correlation of the difference between NCT before and after hypoxia with the difference in DARatio (p < 0.001) and a significant positive correlation with the difference in IntegrRadius (p = 0.023), SPA1 (p < 0.001) and TUC (p = 0.025). The R-squared values of the regression models were 0.6420 and 0.6626 for the bIOP and NCT respectively.
Conclusion
We demonstrated reduction in IOP after hypoxia exposure. A combination of alterations in corneal biomechanics explain a degree of this IOP reduction, whereas CCT did not have a significant role in IOP changes.TUC was found to significantly correlate with IOP changes.
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