Benign essential blepharospasm (BEB) [MIM:606798]: A primary focal dystonia affecting the orbicularis oculi muscles. Dystonia is defined by the presence of sustained involuntary muscle contraction, often leading to abnormal postures. BEB usually begins in middle age. Initial symptoms include eye irritation and frequent blinking, progressing to involuntary spasms of eyelid closure. Patients have normal eyes. The visual disturbance is due solely to the forced closure of the eyelids. In severe cases, this can lead to functional blindness. Note=Disease susceptibility may be associated with variations affecting the gene represented in this entry.