Why does my optometrist get a "co management fee" when he sends me to get surgery with an Ophthalmologist?

I live in New York City and my optometrist sent me to an MD to get cataract surgery. He told me that he gets a comanagement fee from the M.D.(basically a cut of the surgery) I thought the stark law prevented doctors from getting co management fees from other doctors. He told me that it was done so patients don't have to go miles to get followup care from the surgeons in rurul areas. I live in New York City. Sounds like a kickback to me!