This report describes the ocular manifestations observed in alert humans when the diencephalon and mesencephalon were electrically stimulated through chronically implanted depth electrodes. Stereotactic neurosurgical operations were done in 18 persons with intractable pain and involuntary movement disorders. Lesions for the relief of symptoms were localized to the thalamus, field of Forel H, and mesencephalic tegmentum and resulted in specific disorders of the eyes. Contralateral and ipsilateral conjugate eye movements resulted from diencephalic and mesencephalic stimulation. Pupillary dilation resulted from diencephalic stimulation while constriction occurred with midbrain stimulation. Following a unilateral lesion in the midbrain for relief of intractable pain, there occurred nystagmus retractorius, retraction nystagmus, convergence nystagmus, and pupillary abnormalities. A unilateral lesion in the fields of Forel H resulted in a temporary loss of downward conjugate gaze, miosis, and lack of convergence.
Nashold BS, Gills JP. Ocular Signs From Brain Stimulation and Lesions. Arch Ophthalmol. 1967;77(5):609-618. doi:10.1001/archopht.1967.00980020611009