Natural History and Genetic Studies of Usher Syndrome

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The study involved a first visit with ocular exam and assessment of visual function, audiological and vestibular evaluation, and a blood sample for the purpose of molecular (DNA/genotyping) testing. The ocular examination included an assessment of: Best corrected visual acuity with manifest refraction A slit lamp examination and photography of lens opacity, if present Visual field examination (Goldmann visual field) Dilated ophthalmoscopic examination (2.5% phenylephrine and 1% tropicamide) Electroretinography (ERG) Fundus photography of retina, macula, and optic nerve Fluorescein angiography/ocular coherence tomography if macular edema is suspected. Auditory function were evaluated using the following battery of tests: Pure tone thresholds by air and bone conduction for 125-8000 Hz. Speech recognition threshold Word recognition ability Tympanometry Middle ear muscle reflex assessment Distortion product otoacoustic emissions (DPOAEs) Threshold equalizing noise test (TEN) Vestibular function were evaluated using the following procedures: A Videoonystagmography battery of tests including (a) oculomotor tests, (b) spontaneous, positional and positioning tests, and (c) caloric stimulation Rotary chair eye movements Vestibular evoked myogenic potentials (VEMP) Computerized dynamic platform posturography (CDPP) A total number of 196 participants have been enrolled in this study with an accrual ceiling of 400 (200 affected participants and 200 unaffected participants). A total of 188 participants have enrolled at NIH. A total of eight (8) participants have enrolled at the collaborative site, Queens College of the City University of New York (CUNY). There are currently a total of 124 affected and 72 unaffected participants enrolled. There were 21 new participants enrolled in the protocol within the last year. Genotype-phenotype correlations have been performed for some of the genotypes. Usher type I patients homozygous for the R245X mutation of PCDH15 appear to be severely affected from early in life when compared with the rest of Usher type I patients. In Usher type 2A patients, visual acuity decreased and visual field constriction was found to be age-dependent. Computerized dynamic posturography, not previously performed on Usher patients, has provided new information about the vestibular function of both types of the syndrome and might be a useful tool in the rehabilitation of these patients.