A recent NASA study that showed astronauts who have
spent more time in space are more likely to have cataracts
will pave the way for developing new techniques to protect
space travelers.

A research team led by Dr. Francis A. Cucinotta of the
Radiation Health Office at NASA’s Johnson Space Center in
Houston studied 48 cataract cases in current and retired
astronauts. The team discovered a significant increase in
cataracts for those who had higher “lens doses” from space
radiation. They also found those exposed to higher amounts of
space radiation got cataracts at a younger age than
astronauts who received lower dosages.

The team linked the increased incidence of cataracts to the
presence of heavy-ion radiation in space — outside Earth’s
protective atmosphere. The study suggests that long-duration
space station crewmembers are at higher risk for cataracts
than space shuttle astronauts. In the past, space shuttle
crewmembers spent less time in space and often in lower
inclinations where Earth’s magnetic field offers some
protection from radiation.

NASA is developing countermeasures to further protect space
travelers. These include reducing exposure to ultraviolet
(UV) radiation from sunlight, use of selective UV-blocking
eyewear, adding shielding on the International Space Station,
and conducting research to investigate the effectiveness of
anti-oxidants like vitamins C and E and beta-carotene in
slowing the progression of age-related and radiation-induced

Research studies on cataracts and the effectiveness of anti-
oxidants will be performed by NASA-funded investigators at
Brookhaven National Laboratory in Upton, N.Y., where particle
accelerators can reproduce the high-energy heavy ions that
occur in space.

NASA already is improving the space station’s existing
radiation shielding, especially in the living areas like the
sleeping quarters and the galley where astronauts spend most
of their time. Materials with high hydrogen-content like
polyethylene have been shown to reduce radiation. NASA also
actively monitors space radiation levels so astronauts can
move to the best-shielded locations if radiation levels
increase because of solar disturbances.

In addition, NASA follows standard radiation-protection
practices recommended by the U.S. National Academy of
Sciences Space Science Board and the U.S. National Council on
Radiation Protection and Measurements to determine acceptable
levels of risk for astronauts.

To help protect astronauts’ health, NASA is improving the
astronaut optometric exam to include digital imaging and
analysis of the crystalline lens of the eye. This will allow
NASA to better understand the different types of cataracts
occurring in astronauts and their progression from mild to
more severe.

This current study was not able to determine whether
astronauts as a group are more susceptible to cataracts than
other people, since good vision and health are two criteria
for astronaut selection. However, NASA is reviewing a
proposal to perform a follow-on study that would compare
astronauts to a group of people with similar characteristics
who have not participated in space missions. Results from
this study should be available in three to five years.

The results of the study, Space Radiation and Cataracts in
Astronauts, by F. A. Cucinotta, F. K. Manuel, J. Jones, G.
Iszard, J. Murray, B. Djojonegoro and M. Wear, have been
published in the November 2001 issue of the journal Radiation
Research. An abstract of the study is available on the
Internet at: