In some cases, such as refraction, the services were never typically covered by health insurance but had generally been performed gratis as part of an exam. In others, the fees are novel constructs. In any case, as insurers and providers fight over revenue in an era of cost control, patients often find themselves caught in the middle, nickel-and-dimed.

Some of the charges come directly out of patients’ wallets at the time of treatment and catch patients off guard. And if they do not write a check for the refraction fee, for example, many doctors will not dispense a prescription for the glasses.

When Laura Gottsman took her 15-year-old daughter to the Palo Alto Medical Foundation in California last month with a broken arm, she had to sign a special form agreeing to pay for the sling if the insurer did not. A sling charge? Both of her daughters previously had broken arms set at the clinic, and she had not encountered such forms or charges.

“There really wasn’t an option to say, ‘No, I don’t want the sling,’ ” she said. She had not yet received the bill. Liz Madison, a spokeswoman for Sutter Health, which owns the clinic, said that a sling counted as a type of durable medical equipment and that patients typically paid for such items.

Cindy Weston of the American Medical Billing Association, an industry group, said it was up to physicians to decide what to include in their principal payment and what merited an extra charge. She said they now “may be forced to charge” for new services because the Affordable Care Act “has shifted so much responsibility for payment from insurers to patients” and patients do not pay as reliably as insurers.