It was also explained in that episode that he can selectively look at different parts of the spectrum.

The dialog says something like "picking out a conversation in a crowded room."

Pfft, Geordi is the least of Worf's problems at that table. Data is literally a walking computer, Troi can read minds, and Riker is evidently the greatest poker player who ever lived.

There was also an episode where he explained he could see through the cards to discern their values.

He doesn't look until after the hand ends... or so he says.

Oh, you sweet summer child.