1. To be unable to see because the sun is shining directly into one's eyes. I have the sun in my eyes—can you read that sign? My mom hates having the sun in her eyes, so she keeps her sunglasses with her at all times.

2. To be drunk. The phrase might refer to the unsteady gait of one who is drunk (likened to one who is blinded by the sun). A: "Don't mind him, he just has the sun in his eyes." B: "Seriously? How is he drunk already?"