A girl sitting at a desk holds a stereoscope with a card in it up to her face.

“What do you see?”

By Hannah Landecker ~

Originally published in Hidden Treasure: The National Library of Medicine, 2011.

A girl sitting at a desk holds a stereoscope with a card in it up to her face.
A young girl does corrective exercises for strabismus, using a stereoscope, ca. 1940
National Library of Medicine #52331180R

Most people have two eyes directed forward. In ophthalmology textbooks one is asked to imagine a line drawn from each eye to an object on the horizon: two parallel lines representing two lines of sight are blended by muscular and neural processes into a single image—binocular vision with depth perception. When the lines are askew, both eyes do not fix on the same point. It is hard to live with the ensuing double vision; the image from one of the eyes is suppressed by the brain, and instead of seeing double the person literally sees single. Thus “strabismus”: deviation of one visual axis in the normal visual act, also referred to as “squint” and other colloquial terms that manifest the cosmetic dismay that has always accompanied the condition—lazy eye, boss-eyed, cross-eyed, walleyed, cockeyed.

Pavlov’s influential work on acquired conditioned reflex suggested that the eye and brain could be retrained with repetitive exercises, particularly in young children. In 1927 Carl Hubert Sattler (1880–1953?), a Königsberg physician, produced an inexpensive set of stereo-scope cards for the diagnosis and treatment of juvenile strabismus at home, subsequently widely translated and reprinted. This edition of Stereoskopische Bilder für schielende Kinder was published in Stuttgart, Germany by Ferdinand Enke in 1942.

The cards come in pairs that, viewed through a stereoscope, make a composite picture. An umbrella handle is bereft of its canopy. The strabismatic child will see only the handle or the canopy. Asking her what she sees will indicate which eye is fixing on an image and which is suppressed. Bringing the images together—seeing the umbrella whole—is the therapy. According to Sattler, other stereoscope cards, featuring abstract shapes, were hard for children to relate to or describe. Thus the sad moon, the chick following the rooster, etc., were designed to make these exercises fun—though generations of children struggling to put the broom in the snowman’s hand might testify differently. An accompanying booklet told parents and physicians what to ask with each pair, often beginning with the phrase “What do you see?”

Fifteen pairs of cards with separated and complimentary pictures of fruit, figures, animals, and shapes.
Selected pairs of strabismus diagnostic and exercise cards. Stereoskopische Bilder für schielende Kinder, 1942
National Library of Medicine #52331180R

British stereoscope cards produced during World War II show airplanes with parachutists descending from them. Sattler’s cards, designed in the 1920s, betray no hint of the historical circumstances of the year of their reprinting: the duck still opens its beak, the frog still jumps through a hoop. Nonetheless ophthalmology was profoundly changed by National Socialist policies regarding Jewish doctors and scientists; by 1942 Sattler was one of the few strabismus specialists left in Germany. Debates over the causes and etiology of strabismus often mentioned hereditary factors and neurotic instability—the very terms “lazy eye” or “boss eye” suggest constitutional failure. To have such a condition was profoundly dangerous; under the Nazis, hereditary conditions associated with undesirable character, even eminently correctable ones, were grounds for sterilization or worse.

When these charming cards were issued, German armies were occupying much of Europe, Hitler had convened the Wannsee Conference to coordinate the Final Solution, and trainloads of Jews and other “enemies” were beginning to arrive at Auschwitz and other death camps.

“What do you see?” The question hangs in the air of historical time with quiet intensity.

Hannah Landecker is Director of the Center for Society and Genetics at the University of California Los Angeles. She is the author of Culturing Life: How Cells Became Technologies. Her research interests include the use of moving images in life science and the history and social study of metabolic sciences.

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