Anterior communicating artery aneurysm presenting as monocular blindness.

Anterior communicating artery (AcomA) aneurysm presenting with rapidly progressing monocular visual loss is rare. We present one such case masquerading as retrobulbar optic neuritis, with no improvement following steroid therapy. Monocular blindness was due to compression of the optic nerve by a large AcomA aneurysm, which was detected after rupture.