It's a simple procedure that has helped millions of Americans see more clearly. Lasik surgery is truly a medical breakthrough.

But when the surgery goes wrong, it can change a person's life forever. That's why the federal government is taking a closer look at Lasik.

Perfect vision in the blink of an eye is the promise and the outcome for about 95 percent of Lasik patients. But the remaining 5 percent end up with strange effects including double vision, night blindness, star bursts and halos.

That's what life looks like for artist Barbara Berney.

"I cannot see to drive. I can't go out for a walk. I can't find my way around dimly-lit building," she said.

Berney's not alone. Abby Ellin says Lasik surgery left her with chronically dry eyes.

"It's just painful and I feel like there is a film around my eye all the time," she said.

Now more than a decade after approving the procedure, the Food and Drug Administration is preparing a nationwide study to see how patients are doing in post-surgery.

Dr. Roy Rubenfeld has performed thousands of Lasik operations. He insists complications are rare.

"The safety profile of this procedure, in my medical experience over a long period of time, has been unparalleled," he said.

Rubenfeld says anyone considering the procedure should know the risks. But even the best preparation can't completely rule out all complications, which is something Berney and Ellin know all too well.

"My vision is a lot like looking through a wrinkled piece of dirty plastic," Berney said.

"I want my glasses," said Ellin.

The FDA wants to hear from more patients who've had a bad experience with Lasik so that it can decide if the warning about the risks involved with the procedure need to be updated.

Most Lasik patients do walk away with crisper vision. But when things go wrong, patients can end up with poor vision even with glasses, pain, glare or painful dry eyes.

And remember this: Lasik isn't for everyone. Experts say one out of four people looking for Lasik should not have the surgery.