The document discusses the Titmus stereotest, which is used to test stereoacuity and depth perception. It consists of polarized vectograph images in the form of a booklet, viewed through polarized 3D glasses. The test contains images of a housefly, animals at varying disparities, and circle patterns where one circle floats in front or behind the others. It is performed at 40cm and tests the ability to perceive depth in images with disparities as small as 40 seconds of arc. One disadvantage is that it contains monocular cues that could provide clues instead of relying purely on stereopsis.