Age wasn't a significant factor in how well the subjects responded to the treatment, though improvements in vision did seem to be tied to the amount of remaining retina that was still salvageable. Since the disease progressively destroys viable photoreceptors -- the cells in the retina that detect light -- the researchers said it may not have been a surprise that patients age 19 and younger had larger visual field recoveries than older patients.
White light sensitivity improved substantially for five of seven patients treated after the testing equipment became available, with benefits only in the treated eyes. The youngest patients enjoyed the greatest gains in sensitivity, the researchers noted.
Another objective measure of vision improvement -- dilation of the pupil -- improved in the injected eye of all 11 patients tested, whereas the untreated eye showed minimal constriction when exposed to light. The most notable improvement in pupillary-light-response sensitivity was in the youngest patient. The 8-year-old recovered nearly the same light sensitivity seen in a group of control patients without vision problems.
The injected eyes of the patients also seemed to possess improved ability to see in dim light settings, and the treated eyes also appeared to be able to fixate on objects better -- benefits that translated into four children able to navigate an obstacle course on their own after treatment with fewer errors and greater speed. Six patients overall were reclassified as no longer legally blind after treatment.
"The visual recovery noted in the children confirms the hypothesis that efficacy will be improved if treatment is applied before retinal degeneration has progressed," Bennett's group concluded.
In the long-term, the researchers hope to be able to administer genetic therapy as soon as a child is diagnosed with this condtion and thus rescue as much of the retina as possible, High said.