The degenerative eye disease choroideremia affects about one in 50,000 Americans. It is a progressive form of blindness in which parts of the eye called the choroid and the retinal pigment epithelium, along with the retina, gradually decay. Ordinarily the epithelium provides materials and protection for the choroid and the retina, while the choroid lines the eye and helps get nourishment to the retina. When these layers start to break down, they can no longer support optical function and vision loss results. The disease runs in families, but the rate and degree of loss varies from person to person. The degeneration is irreversible, and there is currently no treatment that can stop its progress.
Now, however, researchers say a new approach using gene therapy may hold the key to not just stopping the degradation of the eye layers, but restoring sight already lost. Patients are injected with a clean copy of the gene that is damaged in people with the disease. This is intended to supplant the damaged gene and stop the destruction of cells in the eye. The treatment has only been tested in half a dozen patients, but all of them report success. In fact, one of the two patients in the study who had the most advanced choroideremia, with the most profound vision loss, was able to read four lines further down an eye chart six months after treatment, and night vision, in which the loss generally starts, improved in all six subjects.
Researchers warn, however, that these are only preliminary results, and it remains to be seen how well the treatment will work in the long term. In particular, scientists suspect that the treatment slows degeneration, but does not stop it entirely. Even if that is the case, however, the added years of functioning vision are a benefit to patients. Furthermore, the scientists note that the success of this genetic therapy for choroideremia suggests both other avenues to pursue in efforts to battle the disease—which has not proven treatable until this study—and ways to use gene therapy or similar approaches to treat other eye diseases, which may have similar pathologies, be likewise genetically linked, or both.