Neural adaptation to light stimulation in the dark-adapted retina can be demonstrated by double-flash electroretinography. The first flash is a conditioning flash, the second flash is the test flash. Interstimulus intervals are in the range of 0.2 to 30 seconds. Suppression of the response to the test flash is assumed not to be related to photopigment regeneration, as in normal human subjects the recovery after strong conditioning flashes is completed in about 2 seconds. In this paper we demonstrate the results of double-flash electroretinography on four patients, two of whom are brother and sister. Each of them showed a five- to ten-fold prolonged suppression time compared to normal measurements. Clinical aspects of all the patients were a stationary, though fluctuating, subnormal visual acuity of about 0.5, some photophobia, and difficulties in adaptation to changes in luminance levels. We assume that the PERRS indicates changes in the restorative reactions to phototransduction in the photoreceptors, or in the neural transmission mechanism, either in the rod-driven lateral inhibitory neural processes or in the cone-driven rod inhibitory processes, caused by a cone dysfunction.

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Stereovision became a hype when Wheatley presented his theory in 1838. Stereoscopes became popular. Stereoperception was recognized as the ultimate stage of binocular vision in strabismus theories of the 19th century.Stereopsis is assessed as part of the normal strabismologic examination. Most tests depend on the subject’s active response. In babies the assessment of stereopsis is more cumbersome and rarely done outside a research setting.Stereopsis can be demonstrated from the age of around 3 months by FCPL techniques. Interestingly, this can also be demonstrated to a similar degree in babies with infantile esotropia but the number in which this can be done declines rapidly over months. In the age‐old controversy regarding the timing of surgery for this condition the potential for stereovision is rarely taken into account. Yet this may be an important prognostic factor; it would seem that in the presence of demonstrable stereopsis offering very early surgery makes sense. However, a quick and reliable test for stereopsis in babies is hard to find.This part of the work‐shop will look into the history and background of stereotesting, available tests, recent advances and our own research into developing such a test.

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