Washington: A study of astronauts' eyes and brains shows that they are affected after a long space stint. This includes flattening of the rear of the eyeball, bulging of the optic nerve and changes in the pituitary gland and its connection to the brain, according to University of Texas Medical School, Houston researchers.

Researchers performed Magnetic Resonance Imaging (MRI) and analyzed the data on 27 astronauts, each of whom were exposed to microgravity, or zero gravity, for an average of 108 days. Eight of the 27 astronauts underwent a second MRI exam after a second space mission that lasted an average of 39 days, the journal Radiology reports.

"The MRI findings revealed various combinations of abnormalities following both short- and long-term cumulative exposure to microgravity," said Larry A. Kramer, professor of diagnostic and interventional imaging at the Texas Medical School, according to a statement.

Findings included expansion of the cerebral spinal fluid space surrounding the optic nerve in nine of the 27 astronauts. Flattening of the rear of the eyeball was found in six (22 percent), bulging of the optic nerve in four (15 percent) and changes in the pituitary gland and its connection to the brain in three (11 percent) of the astronauts.

 "These changes that occur during exposure to microgravity may help scientists to better understand the mechanisms responsible for intracranial hypertension (buildup of pressure within the skull), in non-space travelling patients," concluded Kramer.