Inherited retinal dystrophy is a common cause of blindness, with as many as two million people suffering from the disorder globally. No effective treatment is available for retinal dystrophies. Gene therapy is expected to offer a solution, but developing such therapies is possible only when the genetic cause of the disease is known. Related mutations have been identified in more than 70 genes so far, but the genetic background of the disease remains unknown in as many as half of the patients.