I've worked at practices (none eye related) that have done it both ways. I personally prefer NOT to collect deductibles at time of check in. Here's why:
1) Perhaps pt saw another clinician last week and that claim will be processed before yours.
2) You need to know to the penny what the insurance allowable is for each of the codes (for services you haven't even provided yet at check in).
3) You need to know (again to the penny) how much deductible is left.
4) If your fee schedule is not up to date, patients may still have balances, or may also owe for co-insurance.
5) You wind up having to write an awful lot of refund checks which to me is a pain you know where and causes angry phone calls.
Unless you have a patient population that is non-compliant with paying bills, I prefer to inform the patient at check in about the possibility of a deductible, and let the insurance decide exact patient responsibility. Another option is to collect a "deposit" of a set amount if you know there is definitely a deductible of at least a certain amount, again making sure patient understands they will be billed the remainder as determined by their insurance plan.
Side note - most billing software can tell you not only eligibility, but also the deductible and amount left. If you go the route of collecting deductible or a deposit, check with your vendor about that feature.