Publication Exclusive: Monitoring long-term effects on vision in microgravity a priority for NASA’s future flight to Mars

NASA is banding together with thought leaders in ophthalmology and industry to try to remedy vision problems encountered by astronauts in space for lengthy periods of time. The hope is that in-flight monitoring and treatments will counter the detrimental effects of living in essentially a gravity-free environment.

“When you are in space, you do not have gravity like we do on Earth,” OSN Chief Medical Editor Richard L. Lindstrom, MD, said. “In the head, gravity assists blood return to the heart. But in weightlessness, not only is this assist absent, but up to 2 L of fluid shifts headward from the lower body. The core etiology is probably related to elevated venous pressure, which then causes an elevated cerebral spinal fluid pressure. This can result in disc edema and choroidal swelling.”

Richard L. Lindstrom

Lindstrom is one of a handful of ophthalmologists and industry leaders with diverse backgrounds who convened twice last fall as part of a special advisory group to the National Space Biomedical Research Institute (NSBRI) in Houston, a NASA-funded consortium.

“After 8 to 12 weeks in space, some astronauts start to shift hyperopic, developing blurry vision at distance,” Lindstrom said.

The cause is swelling of the choroid, flattening of the globe shortening the axial length of the eye and sometimes associated disc edema. “This presents additional requirements for corrective lenses inflight for astronauts as they try to do their work,” Lindstrom said.

Some astronauts who have experienced disc edema have also had suggestive mild transient visual field defects. However, after returning to Earth, “they do not demonstrate any permanent vision loss, at least so far,” Lindstrom said. Returning to space a second time may exacerbate the situation.

NASA’s Journey to Mars is targeted to get underway around 2030, with the roundtrip journey taking up to 950 days. With such a long flight, there is concern that the astronauts’ vision might progress to severe visual loss or even blindness. “To date, there have been no solutions,” Lindstrom said.

Through a literature search, Lindstrom and others have found rare instances of a similar syndrome on Earth with progressive hyperopic shift, papilledema and choroidal swelling. The condition is called “idiopathic benign progressive hyperopia with choroidal folds and papilledema” and has been reported in a small number of patients not exposed to space travel. The cause of this condition is unknown, but this Earth-bound syndrome and the space-induced changes seem similar.

Overall, it appears men are more prone to developing vision problems in space. NASA medical researchers have found that the cardiovascular risk profile among male astronauts, although clinically normal, is higher compared with female astronauts, suggesting that men may have slightly stiffer blood vessels that may contribute to higher cerebral spinal fluid pressure in space.

Unique technologies

In addition to NASA medical monitoring and a significant research effort in ocular health, NASA has asked the NSBRI to participate in this ocular research effort. NSBRI began in 1997, but it has only been since October 2014 that the institute emphasized ocular health, starting with its Vision for Mars Challenge to accelerate unique technologies for both space and terrestrial applications. In addition to funding by NSBRI for three selected companies, money was earmarked for medical community education, including a workshop, for a total of close to $500,000 to date, according to Dorit B. Donoviel, PhD, deputy chief scientist and industry forum lead at NSBRI. The grants awarded were matched at 100% by private funds, creating a unique public-private partnership.

Click here to read the full cover story published in Ocular Surgery News U.S. Edition, June 25, 2015.