| Along with the development of spaceflight technology, to enter outer spaceis not a privilege of a few professional astronauts. Some scientists, as payloadspecialists, have called at the microgravity environment, and have worked, livedin space station for a long time. Outer space exploration with participant ofeveryman has been realistic, and commercial space flight is becoming a populartopic. That is one of the people's final intentions to explore the outer space. Butthe difference of systemic health condition between payload specialist, touristand professional astronauts is largish, so how to select the person who not onlywill adapt to the microgravity situation, but also will excelwork in microgravitysituation is an austere challenge in front of the aerospace medical specialist.Several epidemiological studies have shown that presence of glaucoma issignificantly associated with the myopic refractive error, age, and lOP. For thepayload specialist or tourists astronauts, the risk factor of glaucoma and opticnerve damage may be possess simultaneity if they entry microgravity situation.firstly as a specialist of some knowledge, he or she should have higherdegree ofeducation and should have had worked in near distance for long time, so they might be have myopic refraction error with different degree. Secondly thepayload specialists have to study, work and train for a long time beforeparticipate in the space mission. Finally when people enter into the microgravitysituation, the IOP will be increased rapidly and will be maintained for a time. Sowe could regard that microgravity situation is an impotent provocative factor toincrease of IOP, payload specialist or tourist astronauts with determinate age andrefractive state, once entered into the microgravity situation, the risk of ocularhypertension or glaucoma is existent and might cause incapacity in space flight.Considering the emotion tension, work load, circadian rhythms and otherelements, the possibility of happening above dangers will be higher. However,the method that ai(?)d to predict the happening of glaucoma during space flightin earth situation is infrequent. Diagnostic methods and provocative testing forglaucoma that have been applied in clinical practice, do not consider theinfluence of microgravity, and a few IOP measurement in the clinic office isprobably not adequate for the optimal management of glaucoma, say nothing ofspace flight situation.The purpose of the present investigation was to study the changecharacteristic of IOP and OPP in subjects with different refractive state during21rain of the -15°HDT bed rest, more specifically to pursue a predictor forhappening of ocular hypertension and glaucoma before the payload specialist ortourist astronaut entry into microgravity situation.Material and Methods1. To study the change of IOP and OPP of sixty five healthy subjects(students of Fourth Military Medical University, age from 22 to 23 years) during-15°HDT 21min, analysed the characteristics of lOP and OPP change insubjects with different degree of myopia. 2. Studied the change of IOP and OPP of sixty one healthy subjects, whointend to take LASIK, during -15°HDT 21min, analysed and estimated thecharacteristics of IOP and OPP change in subjects with moderate and highdegree of myopia.3. Studied the change of lOP and OPA in hundred subjects with differentdegree of myopia pre-LASIK and post-LASIK, estimated the difference of IOPand OPA in subjects with different degree of myopia; studied the influence ofLASIK on IOP and OPA.4. To observe the change of BPV and BRS in myopia and emmetropiasubjects before, during and after -15°HDT 21 min, estimated the possibleabnormalitiesof blood pressure auto-regulation in myopia subjects.Results1. The mean values of IOP had significantly increased in all eyes during-15°HDT tests, the peak values of IOP had been observed at 6min inemmetropic, low myopic and moderate eyes; however the mean values of IOPwere increased with the HDT time in high myopic eyes. The mean values of IOPand IOP in moderate-to-high myopic eyes were significantly higher than inemmetropic and low myopic eyes. Mean values of OPP were significantlydecreased in moderate-to-high myopic eyes compared with emmetropic and lowmyopic eyes during -15°HDT test. Mean values of SBP, DBP inmoderate-to-high myopic subjects were lower than emmetropic and low myopicsubjects during -15°HDT test, the variable of SBR DBP were minimum inmoderate myopes, but the differences were not statistically significant.2. Eliminated the influence of cornea, the mean values of IOP inmoderate-to-high myopic eyes were significantly higher than in low myopiceyes, meanwhile the mean values of OPA were significantly lower than low myopic eyes; After LASIK, the mean values of IOP and OPA inmoderate-to-high myopic eyes were still higher than in low myopic eyes, but thedifferences of IOP were not statistically significant.3. The mean values of HF/LF in myopes were significantly higher during-15°HDT, meantime, the mean values of HF in myopes were significantlylower than in emmetropes, the mean values of LF were closely in all subjects;the mean values of BRS in myopes were lower than in emmetropes, but therewere not statistically different.Conclusion1. The IOP in eyes with moderate-to-high myopic refraction error wassignificantly higher than in emmetropic and low myopic eyes during -15°HDT21min; The OPP in eyes with moderate-to-high myopic refraction error wassignificantly lower than emmetropic and low myopic eyes during -15°HDT21min;2. Before LASIK, the mean values of IOP in moderate-to-high myopic eyeswere significantly higher than in low myopic eyes, the mean values of OPA inmoderate-to-high myopic eyes were significantly lower than in low myopic eyes;LASIK was able to advance the visual acuity, but could not to improve IOP andOPA for myopes.3. Abnormalities of blood pressure auto-regulation in subjects withmoderate-to-high myopic refraction error might be interpreted as a factor for thepathogenesis of IOP increase and OPP decrease during HDT;4. Measured IOP during -15°HDT 21min repeatedly might be applied inpredict of the IOP and OPP for payload specialist and tourist astronauts duringspace flight. 5. Values of IOP by NCT and DCT were significantly correlated with centralcorneal thickness and corneal curvature; values of OPA by DCT weresignificantly correlated with degree of myopic refraction error.
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