Active - Task currently funded
Over the last 40 years there have been reports of visual acuity impairments associated with spaceflight through testing and anecdotal reports. Until recently, these changes were thought to be transient, but a comparison of pre and postflight ocular measures has identified a potential risk of permanent visual changes as a result of microgravity exposure. There are limited pre and postflight measures to define the risk and very few in-flight measures. These data show that there is a subset of crewmembers that experience visual performance decrements, cotton wool spot formation, choroidal fold development, papilledema, optic nerve sheath distention and/or posterior globe flattening with varying degrees of severity and permanence. These changes define the visual impairment/intracranial pressure (VIIP) syndrome. It is thought that the ocular structural and optic nerve changes are caused by events precipitated by the cephalad fluid shift crewmembers experience during long-duration spaceflight. It is believed that some crewmembers are more susceptible to these changes due to genetic/anatomical predisposition or lifestyle (fitness) related factors. Three important systems, ocular, cardiovascular, and central nervous, will be evaluated to understand the risk of developing the VIIP syndrome. Several hypotheses have been proposed to explain the identified visual acuity and structural changes including increased intracranial pressure, localized ocular changes such as ocular hypotony, decreased venous compliance, and alterations in cerebrospinal fluid dynamics. As there is little data to determine the extent or cause of the VIIP syndrome, there is a knowledge gap related to etiology of the changes and the postflight resolution. This lack of knowledge gives the basis for increased pre, in-, and postflight monitoring to characterize the risk. It will be very important to determine the risk of developing the VIIP syndrome and if there is an increase in severity corresponding to mission duration for exploration class missions.
The VIIP evidence book will capture the current evidence for the risk and outline potential hypothesis and future research areas.