Hypobaric hipoxia. effects on contrast sensitivity in high altitude environments

BACKGROUND: Effects of hypobarism and hypoxia on visual performance and mainly on contrast sensitivity (CS) are well known. The purpose of this study was to compare the adjustments of corneal thickness in hypobaric hypoxia conditions with changes in contrast sensitivity. METHODS: There were 12 healthy, emmetropic subjects assigned to the 14(th) Wing Aircrew based in Pratica di Mare AFB (Rome, Italy) who were evaluated for changes occurring in central corneal thickness (CCT), measured by portable ultrasonic pachymeter, and CS, assessed after reading the standard Pelli-Robson charts, during modification of atmospheric pressure and, therefore, of oxygen partial pressure. RESULTS:Hypobaric hypoxia conditions in pilots raised CCT (550 μm to 600 μm) and reduced CS (1.95 log to 1.05 log) in a statistically significant result. DISCUSSION: The study demonstrated that hypoxia and variations of atmospheric pressure may produce corneal edema, including changes of CCT and, correlatively, CS reduction.