Results of a study using gene therapy to reverse the effects of blindness in patients with a rare genetic disease have been unveiled in Philadelphia.

PHILADELPHIA, PENNSYLVANIA, UNITED STATES (OCTOBER 22, 2009) REUTERS - It was an emotional reunion for ten year old Corey Haas, his parents and the doctors who restored his sight. They had
assembled at the Children's Hospital of Philadelphia to announce the successful results of a groundbreaking gene therapy study that has reversed the effects of blindness in Corey and other subjects, with a rare congenital disease. The findings were revealed in a news conference at the hospital by Doctors Jean Bennett and Kathy High, co-authors of the study. Corey Haas was the youngest participant, being eight years old at the time.

By injecting genes that produce light-sensitive pigments into one eye of each subjects, the doctors were able to witness the amazing results:

"The layman explanation is, somebody who was blind can see," says Dr. Kathy High, a co-author of the study.

The study focused on a group of 12 subjects ranging from 8 to 44 years of age, all with a very rare condition called Leber's Congenital Amaurosis (LCA), one of the more than 200 genetic causes of blindness. LCA is so rare that only five babies in the United States are born every year with it, and so finding funding for the study from major pharmaceutical companies was impossible. The hospital decided to team up with the University of Pennsylvania Medical Center, and the gene-injecting surgery was performed in October 2007.

Since the surgery, each of the subjects' vision has improved dramatically, displayed in two videos that show Corey Haas maneuvering his way through two obstacle courses. In one video, his treated eye is covered and he must use what he describes as his "bad" eye, and he is unable to complete the course. In the second video using his treated "good" eye, Corey, who used to be almost completely blind, completes the course with ease.

For Corey Haas, the results are best seen while he is playing outside.

"Well, I just like to ride my bike." says Corey Haas. When asked if he couldn't ride before his surgery, he responds, "Yeah, but I just rode it in front of the house, now I ride all around the block."

Gene therapy can have its risks. In 2001, an 18 year old man being treated for a liver disease died from complications resulting from gene therapy treatment, an incident that put the practice in jeopardy. Since then, more stringent regulations have been put into place, and the doctors for the Philadelphia study made safety a top priority for the test subjects.

"Well, of course we were well aware of the details that were made public about that other very, very sad, unfortunate case," says Dr. Jean Bennett, a co-author of the study, "the regulatory system was ramped up after that unfortunate event, so the net result is that we approach this with as much caution as we could conceivably think of."

For Corey Haas' parents, the benefits of their son participating in the surgery far outweighed the risks.

"Well, he may go blind in the future anyway because it's degenerative, so I decided to try it now and see if we could stop it and correct it, and it was definitely worth the risk," says Ethan Haas, father of Corey Haas.

"It's hard to see a child not be able to play like he should with his other friends, and then to have shortly after surgery, he's out there with his friends, playing, being able to see things coming from his peripheral vision, noticing other kids, it's all worth it," says a teary-eyed Nancy Haas, mother of Corey Haas.

Although this is a major breakthrough for the medical community, the study's author want to steer clear of using the word "cure" to describe the gene therapy's outcome. They are hopeful that the findings will open the doors for further use of gene therapy, and eventually be able to treat other causes of blindness, and other diseases as well.