1. Open opencards file in impress.
2. Copy all cards into clipboard
3. Paste cards into Openoffice
4. Export file as Text file
5. Open Text file in Text editor
6. Find and replace all ";".
7. Find all question and answer fields and seperate them by ";"
8. Import into Anki.
There also seems to be a way to do this by converting the slides to powerpoint, then using this macro. I'm giving up for now. Any more hints would be appreciated, because I still have tons of cards! :)