A month or two back there was a news article (or several) about how spending long-duration flights in space caused astronauts’ eyesight to deteriorate. Since “long-duration” in this case means flights of over a month in low earth orbit the doctors who published the study were rightly concerned about the effect a longer trip in space might have on the astronauts making it; any exploration of the solar system outside of the Moon’s orbit is going to involve flights lasting many months, meaning that this symptom of time spent in low-G environments – which wore off after the astronauts had spent a week or two back on Earth – might suddenly become a hugely relevant problem. However, while I completely get that this is a bad thing that must be avoided or mitigated if at all possible, when you stack it up against the other hazards involved in true long-duration space flights it starts to look positively benign. If only cataracts were the worst an extended journey in interplanetary space could do to us. Unfortunately it’s not quite that simple.