'Tis the season for elective surgery. Or eyeglasses. Or dermatology or dentistry.

Medical care providers say the year-end produces a boomlet of patients calling for last-minute appointments. Their motivation: trying to spend money left in employer-sponsored health-care spending accounts, or squeezing in one more visit before the new year brings a renewed obligation to pay insurance deductibles.

"I can remember not too many years back when you used to be able to put up a 'gone fishing' sign in December," said Mark Davis, manager of Apex Optical Co.'s store at Wisconsin Avenue NW near Tenley Circle. But now the store enjoys an uptick in business in December from customers buying eyewear to use health-care spending account funds they would otherwise lose, he said.

"People are coming in here and saying, 'I've got to spend it, and I don't want to get my teeth fixed,' " said Davis, who added that the increase begins in the first week in December. "We had someone in here last week who got his wife a pair, a pair for his daughter and a pair for himself," he said.

Flexible spending accounts for health-care or dependent-care expenses have been allowed by law since 1978, but they grew in popularity in the 1980s, when the Internal Revenue Service provided employers with guidance on how the plans should operate.

The plans allow employees to set aside pretax dollars--thus reducing their taxable income--in an account that can be used to pay health-care bills their insurance doesn't cover. These include deductibles, co-payments or expenses that normally wouldn't be covered, such as designer eyeglass frames or cosmetic dermatological procedures and prescriptions.

Leftover funds revert to the employer at the end of the year.

Employers like the plans because they reduce the total payroll they pay taxes on, and because they are popular with workers, said Tracy Cassidy, a consultant with William M. Mercer, an employee-benefits consulting firm. According to Mercer, 56 percent of the employers they surveyed provided health-care spending accounts in 1998, up from 53 percent the year before.

About 19 percent of employees take advantage of the benefit, setting aside an average of $930--up from $792 in 1997.

About 4 percent of all health-care spending accounts remain unspent at year-end. Employers use leftover funds for such items as a television for an employee lounge, said Cassidy. But most simply use the money to offset the administrative costs of the programs, she said.

The IRS doesn't limit the amount of money that may be set aside for health-care spending, she said, but most employers do: to around $2,000 or $2,500.

Some providers say it's the knowledge that the annual insurance deductible begins again in January that fills their waiting rooms. As Richard J. Castiello, a dermatologist in Chevy Chase, put it, "People are funny about medical spending. They don't want to do it" when it's their own money.

CAPTION: Apex Optical optician Garrett E. Drake, left, fits David Foster's glasses before year-end while Foster's wife, Olivia, watches at the Wisconsin Avenue store.