We present the case of a 70 year-old man who presented with several months history of tiredness and lethargy. He had a past medical history of ischaemic heart disease. Examination identified a bitemporal hemianopia. Initial investigations demonstrated hyponatraemia, sodium 117 mmol/L (Reference range 132145) with normokalaemia. Further investigations confirmed hypopituitarism: Short Synacthen Test Cortisol at T=0 min, 125 mmol/L, Cortisol at T=30 mins, 277 mmol/L, free T4 10.9 pmol/L (Reference Range 11.024.0), TSH 0.04 mu/L (0.354.5), Testosterone 0.2 nmol/L (5.728), LH 1.8 iu/L (1.518.0), FSH 3.3 iu/L (2.018), Prolactin 122 mu/L (108576). He was commenced on hydrocortisone followed by thyroxine and testosterone replacement. MRI of the pituitary showed a large pituitary adenoma with suprasellar extension, displacement of the optic chiasm and invasion of the cavernous sinus. He underwent transphenoidal hypophysectomy where the bulk of the tumour was excised. Post-operative radiotherapy was planned for the remaining residual. He was well in the immediate post-operative period but on the second post-operative day developed unilateral right complete loss of vision and a right IIIrd nerve palsy. He was returned to theatre for re-exploration but no complication was found and in particular no evidence of haemorrhage seen. The IIIrd nerve palsy resolved but loss of vision persists. Further MRI of the pituitary demonstrated partial herniation of the frontal lobe into the empty pituitary fossa with downward displacement of the optic chiasm. In addition there were features consistent with a venous cortical infarct of the frontal lobe. Visual field loss is rare following transphenoidal hypophysectomy particularly when pituitary apoplexy has been excluded. Chiasmal traction due to frontal lobe herniation is a further cause though would typically result in a bitemporal hemianopia. We believe that direct arterial or venous infarction of the right optic nerve was the cause of unilateral visual loss. This has not been described previously in this situation.