Change of retinal correspondence in monocularly reduced intensity of stimulus

We analyzed the retinal correspondence with a phase difference haploscope on reducing the stimulus intensity of a monocular image with a series of neutral density filters. Ninety-one exotropes were examined by this method. Five cases changed from normal to anomalous correspondence when the stimulation of the strabismic eye was reduced. Two cases showed anomalous correspondence without a filter, but normal correspondence with a reduced stimulus of the normal eye. All these seven cases showed normal correspondence with any other test. The results suggest that masked anomalous correspondence becomes manifest in some cases when the strabismic eye is stimulated more intensely than the normal eye. These cases display both normal and anomalous correspondence and this condition may be called dual correspondence.