Possible eye infection.
What Does It Mean When My Dog Has Excessive "Sleep" In His Eyes?
Your dog has yellow crust in it's eye... That's all. Go to the vet
There are many different reasons that this could happen, the main is probably allergies.
It means that there "goo" around his eyes. It could be caused by many things.
My puppy a boxer lab mix has sleep in the corner of his eyes, he is 9 weeks old. Is this normal? His next vet appointment is another week away.