Sara R. Zwart*, Charles R. Gibson†, Jesse F. Gregory‡, Thomas H. Mader§,1, Patrick J. Stover¶, Steven H. Zeisel‖ and Scott M. Smith (2017). Astronaut ophthalmic syndrome. The FASEB Journal.
*Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston, Texas, USA;
†Coastal Eye Associates, Webster, Texas, USA;
‡Food Science and Human Nutrition Department, University of Florida, Gainesville, Florida, USA;
§Moab, Utah, USA;
¶Division of Nutritional Sciences, Cornell University, Ithaca, New York, USA;
‖Nutrition Research Institute, University of North Carolina at Chapel Hill, Kannapolis, North Carolina, USA;
#Human Health and Performance Directorate, National Aeronautics and Space Administration Lyndon B. Johnson Space Center, Houston, Texas, USA
During and after missions on the International Space Station, some astronauts experience ophthalmic changes, including choroidal folds, optic disc edema, cotton-wool spots, globe flattening, and refraction changes. Astronauts with ophthalmic issues had significantly higher plasma concentrations of metabolites that are associated with the 1-carbon metabolic pathway than those without ophthalmic issues. We hypothesized that genetic differences might explain the metabolite differences. Indeed, genetics and B vitamin status were significant predictors of ophthalmic issues. We now have developed a hypothesis regarding the mechanisms that link 1-carbon pathway genetics and the condition that we suggest calling, “astronaut ophthalmic syndrome.” We maintain that this condition is genetically predisposed and is associated with endothelial dysfunction that is induced by oxidative stress. Subsequent edema can hinder cerebrospinal fluid efflux and can lead to locally increased pressures in the subarachnoid space within the orbit, which impinges on the optic nerve and/or eye in affected individuals. Confirming this hypothesis will help characterize the genetics of 1-carbon pathway metabolism, homocysteine, oxidative stress, endothelial dysfunction, and cardiovascular and potentially other diseases.