CLRN1 and retinitis pigmentosa: Apart from different genes causing USH1 (MYO7A, USH1C, CDH23, PCDH15 and USH1G), USH2 (USH2A, ADGRV1 and WHRN) and USH3 (CLRN1), the main clinical differences between the three types of Usher syndrome are the time of onset of retinitis pigmentosa (RP), the severity of hearing loss and the status of the vestibular function [1].