Fig. 4: An illustrative case of compressive/infiltrative optic neuropathy in an 8 year old male patient with an optic pathway glioma involving the left optic nerve, chiasm and left optic tract (red arrow and outline).

From the left, the MRI is shown and checkerboard stimuli demonstrating the presentation of the pattern stimulus respectively. The occipital VEP responses are shown at the bottom from the left, middle and right occiput respectively. A No reproducible PR-VEP is evident to left eye stimulation. B A reproducible PR-VEP is seen at the occiput to full-field PR-VEP stimulation of the right eye, however this is best defined over the left- and mid-occiput (red arrow) and attenuated over the right occiput (red asterisk). C Selective right half-field stimulation for the right eye demonstrates a reduced ipsilateral positivity expected (red asterisk). D Selective left half-field stimulation of the left eye demonstrates a preserved positivity (red arrow) similar to the full-field PR-VEP. Overall, PR-VEPs indicate profound macular pathway dysfunction affecting the LE and RE crossing fibres, but relatively preserved RE non-crossing fibres subserving the left half-field.