Eyes + glasses means that he watches over everything that goes on around in the valley.  His glasses have yellow rims which symbolize being corrupt, in two different ways:  all he sees is corruptness, and he sees through the eyes of someone who is corrupt.

Consider what glasses do: sharpen images; provide clearer focus; even changes the appearance of the wearer. Consider, too, where the billboard displaying the ad is located overlooking the valley of ashes, almost God-like. Focus on the entire scene when determining what it means, not just an isolated image. There are a variety of motifs from which to choose: corruption, dishonesty, power, desire. See which one works for you. 

The GOLD or YELLOW rim of the eyeglasses in The Great Gatsby represent the desire for wealth and materialistic things - specifically gained through corruption.   The presence of glasses represents moral blindness.