Specifically, Ibn Isa illustrated the optic chiasm and brain.
From the en.wikipedia.org
The third ventricle is close to the optic chiasm, the point where the optic nerves cross and optic gliomas develop in NF1 patients.
From the sciencedaily.com
The optic chiasm is the crossroad of optic nerves stemming from both eyes and allows the brain to integrate binocular visual information, a crucial process for establishing 3D vision.