Optic pathway glioma (OPG) is a benign tumor that develop along the optic nerve (chiasm, tracts, and radiations) characterized by impairment or loss of vision and may be accompanied by diencephalic symptoms such as reduced growth and alteration in sleeping patterns. OPG are often linked to neurofibromatosis type 1 (NF1). The disease is Monarch Disease Ontology entry MONDO_0016167 (optic pathway glioma). Also known as: glioma of optic tract, glioma of the optic tract, glioma of the visual pathway, glioma of visual pathway, optic tract glioma, visual pathway glioma.