I've done a lot of IC work.
Usually done one of two ways: You're a leaseholder in a commercial location and pay space rent. In the olden days, the entity you leased from would bill your insurance for you (because they billed the glasses and exam together) and they'd cut you a monthly reimbursement check with a statement on what each individual insurance paid for the exam. Nowadays, you have to bill your own insurance because it's easier and mostly done online.
Have you heard of the CMS1500 form?
When I did some IC work, I liked to use Office Ally for insurance billing. They are very inexpensive. You can fill out the CMS1500 form online and they will mail out a hardcopy for you, or can submit electronically with a code listed in the address box. If you call their customer service, they can walk you through it. But, MOST insurances allow you to bill online using their own websites. For instance, Davis Vision is really easy to bill. You just get an authorization number and click a checkbox and hit submit. VSP is harder to bill because their Eyefinity website is less user friendly. Just depends on individual plans. Again, call customer service for each insurance and ASK QUESTIONS.
The second way to do IC is working for someone and that other person bills insurance for you. You're usually paid a flat rate per diem. Sometimes per hour. Sometimes there's a base rate plus bonus incentive. You don't bill your own insurance. You pay no rent.
You are responsible for: Malpractice (professional liability) insurance, licenses and fees, state and federal tax withholding's (including additional self-employment tax), and any other business expenses. Save your receipts. Your business expenses will be listed on Schedule C and you can deduct pretty much everything. Hire a CPA to do your taxes for you, but just keep good records.
At the end of the year, you'll be issued a 1099-MISC form from people you've worked for (excepting those where you made less than $600 for that year). File a tax extension because optometrists are notorious for submitting LATE 1099-MISC forms. I got one in JULY one year!
Make sure you fill out a W-9 form for everyone you do IC work for. That enables them to submit you a 1099-MISC. Also, insurance companies will submit you a 1099 form if YOU bill them. If you work for someone (or a lessor bills for you) that person will submit you a 1099 and not the insurance company. That is, if there's a middle-man, you wont get 1099 from an insurance company.
Do good bookkeeping. Keep track of who pays you cash, credit card, check and if any portion of their bill is paid by an insurance company. That helps!
First years a learning curve! Best wishes.