This report describes an unusual case of a middle-aged man who suffered sub-acute visual loss rendering him blind over a period of 4 weeks, associated with the diagnosis of a right temporal lobe World Health Organization grade 4 astrocytoma (glioblastoma multiforme). Chronic papilloedema had been diagnosed at presentation, and this persisted after his debulking surgery, but there was no radiological evidence of direct involvement (by compression or infiltration) of the visual pathways. This case report describes the sub-acute on chronic nature of his visual loss, and suggests possible causes and preventative measures for visual loss in these patients.