Analysis of allelic heterogeneity in USH2A in our discovery cohort (23 probands with presumed USH2A-related retinitis pigmentosa and no hearing complaint in childhood) revealed that all but one (patient D9) patient harboured at least one ‘retinal disease-specific' or novel (presumed ‘retinal disease-specific') USH2A allele (Table 1). Here, USH2A is linked to Abnormal retinal morphology.