The 1st German-Russian MIR mission 1992 is one result of the agreement about technical and scientific cooperation between Germany and the former Soviet Union. Fourteen experiments have been performed during the 8-day manned space mission, one of which was called "TON": self-tonometry in mu-gravity. A total of 70 measurements of intraocular pressure (IOP) was performed in the SOJUS TM capsule as well as in the MIR space station with the automatic self-tonometer. The first pressure readings 16 min after reaching mu-gravity revealed a 92% rise in the IOP compared to the baseline data on earth followed by an adaptation phase lasting several hours. Important information about the handling of the self-tonometer in mu-gravity was obtained. Its use is also planned for the 2nd German D-2 Spacelab-Mission in March 1993.