Blind before you get to Mars
British astronaut Tim Peak has now spent 100 days in space. He is expected to remain in space for a total of 6 months. The effects of space on the human body have been well documented. The severe side effects on the body include stomach churning motion sickness, muscle wasting and bone thinning.
Recent studies have shown that eyes can be seriously affected too.
Because weightlessness increases the amount of fluid within your upper body, astronauts can suffer from a build up of fluid within the brain, known as raised intracranial pressure. This pressure can be transferred to the optic nerves at the back of the eye causing swelling and compression leading to blurred vision. This is a serious complication in an extreme working environment.
Another observation is that the eyeballs of astronauts become flattened at the back. This causes a shift to long-sighted vision and a change in prescription.
Folds in the layer at the back of the eye known as the choroid have also been observed. (Years ago, I recall an astute fellow ophthalmology trainee answering a question ‘what are the causes of choroidal folds?’ with ‘space travel’.)
Some of these changes reverse when astronauts return to Earth. However, there are reports of permanent eye damage. Especially when space flights are long making manned missions to Mars is especially risky.
Tim Peake is part of the NASA team who are contributing to research into the effects of microgravity on eyes. They are reported to be performing fundoscopy – a detailed examination of the retina. Optical coherence tomography – a non-invasive cross sectional imaging of the retina. A visual acuity test and an Amsler grid test to screen for central visual field of vision disturbances. Tonometry which is a measurement of eye pressures with blood pressure. An ocular ultrasound to image the eyeball in 3 dimensions. And a cardiac ultrasound and trans-cranial Doppler imaging with blood pressure measurement. The results should be very interesting.
Astronauts take extreme risk with space travel and it seems the human body may not be very well adapted to it. It would take approximately 500 days for the round trip to Mars – lets hope our that our astronauts’ eyes can tolerate the journey to see it.