Lee KM, Yoo SJ, Woo SJ. Central retinal vein occlusion following hypobaric chamber exposure. Aviat Space Environ Med 2013; 84:986–9. Background: Mountain climbers who ascend to a high altitude could suffer high altitude retinopathy, which varies from tortuous retinal vessels and hemorrhages to retinal vascular obstruction. As hypobaric chamber training could imitate a fast ascent and could lead to decompression sickness, a simulated flight could also lead to a high altitude retinopathy. Case Report: This paper will present a case of central retinal vein occlusion that occurred after exposure to a hypobaric chamber and Valsalva maneuver. Although the patient was treated with an intravitreal bevacizumab injection, his macular edema was aggravated after a helicopter flight, which involved re-exposure to high altitudes and a Valsalva maneuver. Discussion: Systemic evaluation including blood coagulation and carotid Doppler studies did not reveal any lesion. Notably, central retinal vein occlusion can occur in young, healthy individuals after hypobaric chamber exposure.