The bifocal alternative.
D003261:Contact Lenses / Q000592:standards*; D003263:Contact Lenses, Hydrophilic / Q000592:standards*; D004292:Dominance, Cerebral / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D011305:Presbyopia / Q000628:therapy*; D012029:Refraction, Ocular; D014785:Vision, Ocular / Q000502:physiology*