Success of gene therapy for a form of inherited blindness depends on timing

Using a canine model of the vision disorder Leber congenital amaurosis, Penn researchers found that photoreceptor cells continue to deteriorate after treatment if it is given too late.

Dogs that were provided the therapy when more than 63% of their photoreceptor cells were still present but nonfunctional had great success. The effect of the treatment seemed lifelong, and there was an arresting of the progressive degeneration. But for those dogs that had lost more than half of their photoreceptor cells before receiving the treatment, the disease seemed to continue to progress, despite a short-term restoration of sight.