Keystone Telebinocular Tests of Visual Efficiency #10, DB-5K: A Test Showing Involuntary Urge to Fusion Under Partial Dissociation at Reading Distance
Test 10, DB-5K: A Test Showing Involuntary Urge to Fusion (resistance to diplopia, or double images) under partial dissociation at Reading Distance.
One of the goofier Keystone optical stereograms, this card tests the alignment and convergence of the faces and balls with the potential diagnosis being "Undesirable Tendency."
Keystone View Company (Meadville, PA) published several series of stereoscopic images promoted as optical diagnostic and therapeutic tools in the 1930s and '40s—including the "Eye-Skill Series," "Comfort and Depth Perception Series," and "Betts Ready To Read Tests."
Card slightly bowed (as typical), otherwise VG; 3.5 X 7 inches. Housed in mylar sleeve for safekeeping.