The focus of variable-focus lenses in eyeglasses worn by a person is regulated in accordance with an indication of a spatial relationship of features of the person's eyes to provide an at least partially in-focus image of a feature at which the person is gazing.. The lenses are nematic liquid crystal...http://www.google.de/patents/US5861936?utm_source=gb-gplus-sharePatent US5861936 - Regulating focus in accordance with relationship of features of a person's eyes
