Stereopsis - Stereopsis Tests

Stereopsis Tests

The ability of stereopsis can be tested by, for example, the Lang stereotest, which consists of a random-dot stereogram upon which a series of parallel strips of cylindrical lenses are imprinted in certain shapes, which separate the views seen by each eye in these areas, similarly to a hologram. Without stereopsis, the image looks only like a field of random dots, but the shapes become discernible with increasing stereopsis, and generally consists of a cat (indicating that there is ability of stereopsis of 1200 seconds of arc of retinal disparity), a star (600 seconds of arc) and a car (550 seconds of arc). To standardize the results, the image should be viewed at a distance from the eye of 40 cm and exactly in the frontoparallel plane. There is no need to use special spectacles for such tests, thereby facilitating use in young children. Another common clinical test for stereopsis is the contour stereotests. An example of such tests would be the Titmus Fly Stereotest, where a picture of a fly is displayed with disparities on the edges. The patient uses a 3-D glasses to look at the picture and determine whether a 3-D figure can be seen. The amount of disparity in images vary, such as 400-100 sec of arc, and 800-40 sec arc.