Comes with a pair of red/green glasses (#9397). Lightweight, palm-sized. This ergonomically designed handheld device features 4 peripheral porthole LEDs (Light-Emitting Diodes) and 4 central porthole LEDs with a constant brightness. The peripheral porthole lights test for peripheral suppression; the central porthole lights test for foveal fusion/suppression. A momentary rocker switch allows for peripheral or central testing. The Worthmore II Four Dot Test is powered by two replaceable coin batteries (included).