Wilbrand's knee

Wilbrand's knee 

That portion of the decussating optic nerve fibres from the inferior nasal retina which loop forward into the contralateral optic nerve for a distance of up to 3 mm from the anterior part of the optic chiasma and then pass backward into the optic tract. The existence of Wilbrand's knee in normal subjects has been questioned. See junction scotoma.
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