On the morning of March 20, eye surgeon Jason Comander injected viruses carrying lab-grown genes into the eyes of a boy whose vision had been gradually disappearing.

If all goes as planned, the 13-year-old patient -- who lives with an inherited genetic defect that causes blindness -- will experience an improvement in eyesight in about a month.

After a series of tests, the U.S. Food and Drug Administration (FDA) approved this gene-therapy treatment, called Luxturna, in December 2017.

Three months later, the procedure Comander performed at Massachusetts Eye and Ear served as the first time an FDA-approved gene therapy was used on a person living with an inherited, and incurable, genetic disease. There are no other effective treatments for this specific retinal disease.

"It's a huge step in the right direction," said Comander, associate director of the Inherited Retinal Disorders Service at the Boston-based hospital, in an interview.

"Most of the patients are legally blind by their 20s or 30s," said Comander. "Suffice to say, these are really terrible diseases."

Scientists have been working on this novel type of treatment for decades, including as part of FDA trial programs. Comander notes the treatment affects different patients in different ways. Sometimes the vision improvement is dramatic. One previous patient, from an earlier FDA trial, no longer needed to attend a specialized school for children with blindness, Comander said.

"This has been a dream of the field for 30 years, and there have been sobering setbacks," said Tim Cherry, who researches inherited blindness and other visual disorders at Seattle Children’s Research Institute, in an interview. Cherry disclosed he has collaborated with Comander on research before, but played no part in the development of this treatment.

"It can improve people's lives in a way that might have been considered science fiction years ago," said Cherry. It should be noted, however, that while blind people face challenges due to inaccessibility, many live happy, fulfilled lives.

The rare, mutated gene in afflicted patients, known as RPE65, prevents the retina, a light-sensitive tissue behind the eye, from working correctly. Specifically, the gene prevents retinal cells from properly producing proteins, resulting in deteriorating eyesight. Many patients become legally blind, and some lose all their eyesight.

This novel gene therapy, called gene-replacement therapy, is designed to replace the mutated genes with genes that work, and accordingly, improve a patient's eyesight. Synthetic genes are first grown in a lab and then inserted into viruses commonly found in the human eye. The viruses -- whose mission is to invade eye cells and infuse genetic material into them -- are then carefully placed in the patient's retina.

These viruses, said Cherry, naturally live in our eyes and are harmless.

Because there were no other meaningful treatments available for this incurable disease, the FDA approved the treatments more rapidly than it typically does, under programs called Breakthrough Therapy and Priority Review.

These sorts of accelerated approvals require drug companies and clinicians to continue monitoring the treatments after their initial FDA approval, to ensure they're truly safe and effective enough for consumers to use. The safety warnings on the Luxturna website underscore these potential hazards, including potential eye infections and further declines in vision.

Earlier in 2017, the FDA had approved two other gene-therapy treatments for cancers, which aren't considered genetically-inherited diseases. The FDA now plans for gene therapies to play a more prominent role in combating previously untreatable diseases.

"I believe gene therapy will become a mainstay in treating, and maybe curing, many of our most devastating and intractable illnesses,” FDA Commissioner Scott Gottlieb said when announcing the approval of Luxturna.

Although gene therapies provide treatments for historically unmanageable diseases, they can be markedly more expensive than conventional treatments, especially if the disease -- such as this retinal mutation -- is rare.

The price right now is prohibitively high for most Americans: It costs $425,000, per eye. The pharmaceutical company that produces the treatment, Spark Therapeutics, notes on its website that it assists by directly contacting insurers and offers payment plans.

But Cherry hopes this gene therapy can be expanded to other similar diseases, driving down the cost of artificially producing the genes.

"We’re all in it to try and improve people's lives. So making the treatment more accessible is on everyone’s mind," said Cherry.