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May 1968

Entoptic Visualization and Impletion of the Blind Spot

Arch Ophthalmol. 1968;79(5):589-594. doi:10.1001/archopht.1968.03850040591019

The blind spot of Mariotte can be visible subjectively for as long as 15 seconds at low luminances, and also in the dark. When the adaptation of any part of the visual system is unmatched to the stimulus, either a dark disc scotoma appears on a lit field, or a bright disc scotoma appears on a dark field. Often there is a border contrast phenomenon thought to be indicative of lateral inductance in the cortical fourth order neurons. The scotoma is most slowly filled up at low luminances, and is not perceptible with bright fields unless these have been preceded by prolonged dark adaptation. The initial impletion depends upon the contralateral retina; final "matching" impletion may be made by the complex cells, fifth order, or higher, on signals from the ipsilateral retina, and at the same time supression of the contralateral "nonmatching" signals.