An 18-month-old British girl, Opal Sandy, has undergone a groundbreaking gene therapy trial to treat her auditory neuropathy, a condition that caused her to be born completely deaf. The trial, which used a gene therapy from biotech firm Regeneron, has shown promising results, with Opal's hearing now almost normal. The treatment involves delivering a working copy of the OTOF gene to the ear, which enables cells to communicate with the hearing nerve. This is the first time this type of gene therapy has been used to treat auditory neuropathy.