up to one’s eyeballs

(in) up to (one's) eye(ball)s

Extremely busy; deeply involved or engrossed (in or with something). I'd love to come for a pint, but I'm in up to my eyeballs with work for my class on Monday. John has been up to his eyes with the kids lately.
See also: up
Farlex Dictionary of Idioms.

up to one’s eyeballs

and up to one’s ears
mod. filled up with something. We are up to our eyeballs with trouble around here. She’s up to her ears in marriage proposals.
See also: eyeball, up
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions
See also:
  • (in) up to (one's) eye(ball)s
  • eyeball
  • up to eyeballs
  • up to your eyeballs
  • up to your eyes
  • (in) up to (one's) elbows
  • a busy bee
  • busy bee
  • (as) busy as popcorn on a skillet
  • popcorn