A vision tester having a casing horizontally adjustable with respect to a base. Inside the casing a rotating drum has a first end rotatably fixed to the casing and a second end unconnected to the casing and having an open portion. An illumination device is removably mounted to the casing and inserted...http://www.google.co.uk/patents/US4740072?utm_source=gb-gplus-sharePatent US4740072 - Vision testing apparatus
