Usher syndrome is the most common genetic form of deaf-blindness. This disorder is characterized by congenital sensorineural hearing loss associated with defects in the inner ear, and vision loss associated with retinitis pigmentosa. In most cases, the rod cells are affected first, followed by the cone cells. In some cases, the foveal vision is spared, resulting in a 'doughnut vision'. According to the severity of the condition, three distinct types of Usher syndromes are recognized. Usher syndrome type 1 is the most severe of these different types. Patients affected with this type are born profoundly deaf, and start to lose their vision within the first decade of their life. In addition, problems in the vestibular system are also seen, resulting in patients exhibiting difficulties in maintaining their balance and a significant delay in walking as infants. Approximately, 5% of children born deaf are actually affected by Usher syndrome type 1. Overall, the incidence of this severe type is about 4 per 100,000, although it is more common in certain populations, such as Ashkenazi Jews and the Acadian population in Louisiana.

Since the vision loss does not occur until much later, a diagnosis of Usher syndrome can be missed out in the face of deafness as the only symptom in infancy. Molecular diagnostic testing has the potential to provide an early diagnosis. The condition, however, cannot be cured. Management strategies include cochlear implant, and preparing for blindness before it manifests itself.

Usher syndrome type 1 is further divided into seven different subtypes, depending on the genetic locus involved. Most of these genes code for proteins that play important roles in normal hearing, vision, and maintenance of balance. These include CDH23, MYO7A, PCDH15, USH1C, and USH1G genes. The condition is transmitted in an autosomal recessive manner.

Usher syndrome type 1B is caused by mutations in the MYO7A gene. This gene codes for the Myosin VIIA protein, an unconventional myosin. In the inner ear, this protein plays a role in the differentiation and morphogenesis of the stereocilia, the hair-like projections that function as acoustic sensors. Within the retina, this protein plays an important role in the distribution and migration of retinal pigment epithelial melanosomes and phagosomes, and in the regulation of opsin transport in retinal photoreceptors.