The Food and Drug Administration, which has been investigating patient complaints over the procedure, told health-care providers that commercials and other promotions that do not convey necessary warnings, side effects and other precautions are deceptive.

“Advertising and pro- motional materials for FDA-approved lasers used during LASIK procedures must be truthful, properly substantiated and not mislead- ing,” wrote agency official Timothy Ulatowski.

The letter comes more than a year after the FDA held a public meeting that drew dozens of unhappy patients who complained of blurriness, double vision, depression and other problems after undergoing LASIK.

Surgeons and other industry groups said the procedure is safe and effective when done properly and that most patients are satisfied with their vision afterward.

LASIK involves cutting a flap in the surface of the eye and then using a laser to reshape the cornea, aiming to improve patients’ vision so they can avoid glasses or contact lenses.

About 700,000 Americans have undergone the procedure since it was approved in 1998, industry estimates have shown.

Diana Zuckerman, president of National Research Center for Women & Families, said the FDA could have done more than send a “vague” letter that does not help patients “in any meaningful way.”

“The problem is there are certain people who are unlikely to benefit [from LASIK] and they don’t know who they are,” she said. “At this point, many people think LASIK is some kind of miracle . . . and that’s just not true.”