First Use of Gene Therapy to Treat Sight Disorder

Author:  Hoi See Tsao

Institution:  Wellesley College
Date:  May 2007

Researchers at London's Moorfields Eye Hospital have made the world's first attempt at using gene therapy to treat a visual disorder. The team operated on Robert Johnson, who lives in the UK and has a sight disorder that deteriorates with age.

Johnson's disorder is due to a defect in a gene called RPE65, which stops the photoreceptor cells in the retina at the back of the eye from detecting light. In people with healthy vision, these cells usually detect light. However, as they are damaged in Johnson's case, he is unable to see properly.

The gene therapy administered involved the injecting of normal copies of the defective gene into the back of one of Johnson's eye. The normal gene is injected between two layers of cells that form the retina. If successful, the normal genes will restore the cells in the pigment layer and help the photoreceptor cells in the retina detect light again. The cells can then send nerve impulses to the optic nerve and eventually to the brain and improve Johnson's sight. After the operation, Johnson can currently see outlines during the day but little at night.

The technique has been successful when performed on animals. Johnson is one of 12 patients selected to determine whether the technique will work for human patients as well.

Researchers will not know how successful the gene therapy has been for a few months. If the gene therapy is successful, the team believes that the technique could be used to treat many other inherited sight disorders.

The lead researcher, Professor Robin Ali at the University College London Institute of Opthalmology, has worked on this technique for 15 years. Great precision was required for the surgery, as any mistake could have torn Johnson's retina. Ali's colleague, James Bainbridge, who performed the actual surgery, said, "It is very encouraging that we can deliver genes to an extremely fragile site in the eye without complications."

Professor Andrew George, an expert in molecular immunology at Imperial College London, was also optimistic about the gene therapy. "The eye is good for gene therapy because it is a simple organ and it is easy to see what is going on," said George, "There is hope that once gene therapy is developed in the eye, scientists could move on to more complex organs."

Written by Hoi See Tsao