LASIK isn't always as awesome as we might think.

Millions of Americans each year undergo LASIK surgery to correct their vision. Given how common the procedure has become and how ubiquitous the ads are on radio and TV, you might be tempted to treat the decision to get the treatment pretty casually or think of it as purely a financial decision. A team of researchers from the Food and Drug Administration, the National Eye Institute and the Department of Defense would like to make sure you weigh the potential risks to your eyes more seriously.

In 2009, as LASIK was becoming a household word, the government scientists launched a major study to investigate reports of adverse impacts from the procedure. At the time, there were a lot of anecdotes flying around but little scientific information about patient outcomes. The results, published in October 2014, showed that some patients developed problems that adversely affected their day-to-day lives, such as difficulty driving at night or in sunshine. But it was such a small number — less than 1 percent — of the patients in the study that it was difficult to draw any strong conclusions from that data.

On Wednesday, the group released a follow-up report in JAMA Ophthalmology that provides more sobering information. The study suggests that the percentage of people who undergo LASIK and wind up with new visual symptoms — such as double images, glare, halos or starbursts — may be much higher. The data was based on a questionnaire that looked at patient satisfaction with their vision and at visual and dry-eye symptoms following surgery.

First, the good news. More than 95 percent of participants said they were satisfied with the improvements to their vision. In addition, the prevalence of dry-eye symptoms also decreased after surgery. The bad news is that a “substantial” percentage of the study participants said they had other, new symptoms following the procedure.

The study analyzed outcomes for two groups of LASIK patients. In the first group, which included 262 Navy personnel with an average age of 29.1, it was 43 percent reporting new symptoms. And in the second, consisting of 312 civilians at five practice and academic centers and with a median age of 31.5, it was 46 percent. In addition, about 28 percent of patients who had never had dry-eye symptoms before developed mild, moderate or severe symptoms three months after the procedure.

“To our knowledge, our study is one of the few that have reported the development of new visual symptoms,” Malvina Eydelman of the U.S. Food and Drug Administration and colleagues wrote. “While the overall prevalence of visual symptoms decreased, a large percentage of participants with no symptoms preoperatively reported new visual symptoms postoperatively.”

One interesting component of this study was that the survey showed that the percentage of people with symptoms may be much higher than what has been previously reported in studies involving direct interviews with health-care professionals. The authors of the new study note that the reluctance of patients to tell their doctors about “negative” events has been well documented.

The researchers cautioned that the study may not generalize to the LASIK population as a whole because of its small sample size and short follow-period, which was typically three months. However, they emphasized that “although the magnitude of the development of symptoms is uncertain, patients undergoing LASIK surgery should be adequately counseled about the possibility of developing new visual symptoms after surgery prior to undergoing this elective procedure.”

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