[Self tonometry during the German 1993 Spacelab D2 mission]

Microgravity during space missions leads to a fluid shift from the lower to the upper parts of the body that also affects the intraocular pressure. In the early phase after reaching microgravity there is an intraocular pressure peak. In order to analyse the potential health risks for astronauts, a self-tonometer was developed to examine the early phase of microgravity. During the German-Russian MIR mission the equipment was tested for the first time in space. As one result we found an initial pressure increase of 92% compared to the baseline data values. In order to obtain more detailed information on the intraocular pressure alterations in space, similar equipment was used during the 10-day German Spacelab D2 mission. Two German scientists and one American astronaut obtained self-tonometric pressure profiles on 6 mission days (44 pressure values determined out of 144 measurements). The initial peak values 15 min after entering microgravity revealed pressure increase of 114% compared to the baseline data (average pressure: right eye 10.0 mmHg, left eye 9.9 mmHg; peak values: right eye 22.6 mmHg, left eye 22.2 mmHg). Pressure values exceeding the baseline data by more than 50% were registered up to the 3rd mission day. As to circadian rhythm, there was no difference between inflight data and baseline data before and after the mission.