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

(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

(in something) Go to up to one's neck (in something).
See also: eyeball, up
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

up to your eyeballs

If you are up to your eyeballs in an unpleasant situation, you are very deeply involved in it. He was out of a job and up to his eyeballs in debt. I simply won't have the time — I'm up to my eyeballs in work.
See also: eyeball, up

up to your eyes

If you are up to your eyes in work or in an unpleasant situation, you are very busy with it or are deeply involved in it. I'm afraid I'll be late getting back. I'm up to my eyes in work. He's up to his eyes preparing for the trip. By this time Walker was up to his eyes in debt.
See also: eye, up
Collins COBUILD Idioms Dictionary, 3rd ed.

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:
  • eyeball
  • up to eyeballs
  • up to one’s eyeballs
  • up to your eyeballs
  • up to your eyes
  • (in) up to (one's) elbows
  • a busy bee
  • busy bee
  • popcorn
  • (as) busy as popcorn on a skillet