Abstract
Purpose :
To evaluate the effect of simulated high altitude on intraocular pressure (IOP) in healthy volunteers after 3-hour exposure to 4000m simulated altitude in a hypobaric chamber.
Methods :
IOP was measured with Accupen tonometer at ground level (44m above sea level, Beijing,T1) ,at half an hour(T2),2nd hour (T3),3th hour (T4) during hypobaric hypoxic exposure (equivalent to 4000 m above sea level) and immediately(T5) ,1st hour(T6),3th hour(T7) at ground level again after this exposure. For each condition, the mean of 3 consecutive measurements of IOP was calculated. Central corneal thickness(CCT) was also measured by as-OCT at T1 andT5.
Results :
IOP continually decrease was observed at T2(16.43±3.5mmHg,p=0.049),T3(15.79±3.02mmHg,p=0.006) ,T4(16.11±3.54mmHg,p=0.045) during exposure to simulated high altitude compared with T1(17.27±3.08mmHg),and IOP at T5 was lowest(14.99±2.71mmHg,p=0.000).IOP began to resolve at T6(15.73±2.45mmHg) but still lower than T1（p=0.001) . IOP finally returned to baseline at 3 hour after exposure to 4kmASL (17.47±1.31mmHg,p>0.05). There was no significant difference between CCT in the pre-hypoxic and post-hypoxic conditions (542.56±41.75&538,81±42.87,p>0.05).
Conclusions :
Exposure to simulated 4000m ASL caused a continually significant decrease in IOP in healthy individuals. After 1th hour return to ground level IOP began to recover and would return to baseline at 3th hour .Such IOP changes can’t be solely explained by CCT –related estimation error.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.