A mains electricity (AC-powered) ophthalmic device intended to project an image on a screen to test visual acuity. The images typically include block letters (Snellen chart) and/or other symbols (e.g., recognizable objects used for children who cannot read)...
A noninvasive, hand-held, manual device intended to be used during an eye examination to determine objective and subjective convergence points, examine accommodation, and determine the master eye. Often called a Royal Air Force (RAF) convergence rule or RAF...