Dr. Barry Byrne listens to testimony concerning the approval of a drug for a form of blindness during a meeting Thursday at the FDA in Silver Spring, Md.

SILVER SPRING — A potentially groundbreaking treatment for a rare form of blindness moved one step closer to U.S. approval Thursday, as federal health advisers endorsed the experimental gene therapy for patients with an inherited condition that gradually destroys eyesight.

The panel experts to the Food and Drug Administration voted unanimously in favor of Spark Therapeutics’ injectable therapy, which aims to improve vision by replacing a defective gene needed to process light.

The vote amounts to a recommendation to approve the therapy. The FDA has until mid-January to make its decision and does not have to follow the panel’s recommendation.

If approved, Luxturna would be the first gene therapy in the U.S. for an inherited disease and the first in which a corrective gene is given directly to patients. While the therapy from Spark Therapeutics targets a small group of patients experts say it could pave the way for other genetic treatments for a variety of inherited conditions.

The company says the drug is intended for those 3 years and older. Panelists concluded that the science behind the drug — based on research from the Children’s Hospital of Philadelphia — was remarkably strong with few serious side effects.

Several patients attended the meeting to urge panelists to support the drug, relating experiences of seeing snow, stars and the moon for the first time. In most cases, the patients’ travel expenses were paid for by the drug’s developer.

Katelyn Corey, 24, described her life before the treatment as “a black and white film.”

“Within days of the first treatment I could see vibrant colors again,” Corey said. “I could see the clock tower of Philadelphia City Hall at night when mere days before I thought it was the moon.”