Cüppers' method relies on entoptic phenomena and afterimages to redirect the fixational point back to the fovea. To accomplish this, Cüppers developed the Euthyscope.
The Euthyscope stimulates the retina with bright light while shadowing the fovea, just as the Pleoptophor does.
However, after bleaching the perifoveal region, Cüppers' next step is to occlude the good eye and have the patient become aware of the afterimage of the Euthyscope by looking at a blank screen.
