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.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann