Self-tonometry under microgravity conditions.

Microgravity leads to a "fluid shift" towards the upper parts of the body and, therefore, to a rise of the intraocular pressure. Parabolic flights have also demonstrated some rise of the intraocular pressure. During the first German Spacelab mission D1, changes of the intraocular pressure were investigated for the first time in space. The first pressure readings were obtained 44 min after entering microgravity and showed a pressure rise of 20 to 25% compared to the baseline data. To get earlier measurements in microgravity a fully automatic self-tonometer was developed which functioned independent of position and microgravity. It was used during an 8-d manned space mission in March 1992. Measurements of the intraocular pressure have been performed 16 min after reaching microgravity. The pressure readings revealed a 92% rise of the intraocular pressure compared to the daytime-correlated baseline data on Earth.