Three federal agencies — the Food and Drug Administration, the Defense Department and the National Eye Institute — announced recently they are launching a three-year effort to gauge how many, and which, patients suffer troubling symptoms after undergoing the vision correction procedure called Lasik.

At the same time, the FDA issued letters reminding 17 walk-in surgical centers performing Lasik surgery of their obligation to report poor outcomes and patients’ surgery-related medical complaints. The letters were issued after the FDA conducted a spate of inspections of Lasik facilities and found many had no system for collecting and transmitting to the FDA data on patients’ reports of post-surgical “adverse events.” More inspections are to come, the FDA said.

It has been almost two decades since the laser-assisted in situ keratomileusis procedure was first used in the United States, and between 1.1 million and 1.4 million patients a year now undergo the surgery to correct vision defects.

Aggressive marketing has made Lasik a $2 billion industry, one that has come under criticism for overselling the surgery’s benefits and underplaying its risks.

In May, the FDA circulated a letter to eye-care providers calling attention to “deceptive or misleading health care advertising claims” and outlining the limits of allowable claims that may be made for Lasik.

But while Lasik has many ardent admirers among the more than 12 million in the U. S. who have had it, between 2 percent and 5 percent of patients getting the surgery — as many as 75,000 a year—are thought to have lasting post-operative problems that include painful dry-eye, poorer vision, halos, glare and even blindness.

The FDA calls these “quality of life” problems and has acknowledged that it has recorded no more than a small fraction of such problems during the Lasik industry’s period of explosive growth. (In the 10 years leading to an early 2008 hearing on Lasik, the agency said it had received only 140 reports of post-Lasik eye problems.)

In the first phase of the FDA-led effort to measure Lasik’s effects, the agency is drafting a Web-based survey of patients who have undergone the procedure.

In its second phase, the Defense Department will gauge how many active-duty military patients suffered post-surgical eye problems, and whether certain populations of patients fared worse.

Phase 3, which will end in 2012, is to study a general patient population across the country to determine how many, and who, suffer problems from the surgery.

Dr. Jeffrey Shuren, director of the FDA’s Center for Devices and Radiological Health, says the study likely will identify which patients are at higher risk of poor outcomes and “could lead to a reduction” in those whose eye problems are made worse by the procedure.