You don't say if the output from the optos needs to be steady or if it can be pulsed. If the latter is ok, then you could use a pic to receive the serial data from the pc and convert it to a suitable data stream to send to LED matrix drivers, such as Maxim's MAX6960, 61, 62 or 63. Each of these chips will drive 64 leds at a time (in an 8x8 matrix), but they will be multiplexed. These chips cost about $6 US. You could use any of several other Maxim chips to do the same thing, but their outputs will also be multiplexed. Look for those chips with 8 digits and 7 segments+DP.
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JB