Treating Best Disease with Gene Therapy (IMAGE) University of Pennsylvania Caption Gene therapy successfully treated a canine version of Best disease, a blinding disorder, the effects lasting more than five years. In these images of the retina of untreated (left) and treated (right) dogs, one can see that BEST1 gene expression (in red) was restored following treatment. In addition, the threrapy restored the structure of the RPE (bottom green layer), a layer of cells that supports the light-sensing photoreceptor cells. Credit University of Pennsylvania Usage Restrictions In context of reporting License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.