I would personally consider any eye injury (to human OR pet) as an emergency, since eyes are, you know, rather important...

So when you made this appointment, did you make it clear to the vet's office that this may be an emergency to prevent loss of vision or the eye of the pet?

If not, I would call them back for a much sooner appointment. Antibiotics work much better BEFORE infections become extensive, and for all you know, he may
have debris (a foreign object) in his eye causing the problem. I've had my share of eye injuries (corneal abrasions) over the years...few if any body parts become
infected faster than eyes do, but they also can heal fast with proper & timely medical care by knowledgeable professionals.