Are you sure he 'couldnt' open the eye, not that he 'wouldnt'?
I askm because sometimes in the early morning, my guys will sit with one eye closed for a few minutes, then as they wake up they open both and begin their ritual of exploring their homes and bug hunting, possibly some rubbing and some eye bulging to clean out their eyes.
Did the eye look different than normal? any crusting, oozing, etc?
did he recently shed?
did he bulge the eye out at all?