Clinical and Genetic Testing of Patients With Usher Syndrome

This study is aimed to characterize Russian population of Usher patients. Tasks: Stage 1. Formation of the primary cohort of patients. Patients pre-recruiting will be performed based on Deaf-Blind Support Foundation "Con-nection" patient database analysis. Patients with clinically confirmed Usher syndrome will be evaluated according to available data of the clinical examination. Stage 2. Clinical examination of patients. Each patient will undergo the following diagnostic procedures according to the unified protocol: * Visometry (with correction and without correction) * Ophthalmoscopy * Perimetry * Optical coherence tomography * Electroretinography * Visually evoked potentials * Refractometry * Pneumotonometry * Biomicroscopy * Tonal audiometry * Electronic audiometry (ASSR test) * Acoustic impedance measurement * Vestibulometry * Electronystagmography * Any additional examinations and consultations if necessary Medical record will be developed and maintained for each patient consisting results of extended clinical examination. Stage 3. Genetic study of patients. All enrolled patients will undergo single 4 ml peripheral venous blood sampling. DNA will be extracted from leucocytes. DNA samples will be analyzed and placed for long-term storage in liquid nitrogen. Statistical and bioinformatic analysis of detected genetic mutations in the study cohort will be performed.