Well, the pins are for an electrical S/PDIF connection... you might able to able to get some sort of electrical -> optical hookup. (Usually it's something as simple as a bright LED connected to a jack).
Does the sound card have an optical output? (They look different from most jacks. It looks kinda like the hole that speaker leads would be connected to (by stripping the wires and inserting))
Many stereo system components and DVD players have these connectors. Your soundcard might not.
However, the pinout for the SPDIF header is pretty widely understood, so it should be pretty easy to connect something to it (assuming your speakers can take a coaxial input for SPDIF).
It's possible that your soundcard might have a coax output built in already. Sometimes, it just routes the SPDIF through the regular analog jacks (as is the case with my sound card), you have to turn on an option in the volume settings to enable digital output.
But again, neither of these are optical. You will need to connect the speakers through coax / RCA to get SPDIF input unless you can somehow connect an optical transmitter to the SPDIF output pins.