That's not plywood on petran79's chin house?I would think it's similar to other animals of the same species, humans for example all have roughly the same size eye balls regardless of race, gender, or age. The difference is the skin (and fur) around the eye as well as the size and shape of the skull can vary from person to person or chinchilla to chinchilla making the eyes appear smaller or larger. I could be wrong though I don't have anything to back up that theory about chins eyes but it would make sense to me.
My standard grey does also. In fact he has been the healthiest and most beautiful of the 10 chins I've had over the years, and he came from PetSmart! He's 17 years old and is cute and peppy as a baby. And loaded with personality!My standard grey definitely had bigger eyes and wider nose than my black velvet does.