Due to a lesion anterior to the optic chiasm.
1. Amaurosis fugax: often described as a “shade coming down” over one eye
a) TIA: usually due to occlusion of the retinal artery
b) giant cell arteritis (GCA): usually due to ischemia of optic nerve or optic tracts (less commonly due to retinal artery occlusion) 1).
2. trauma: optic nerve injury
3. ruptured carotid cavernous aneurysm: resultant carotid-cavernous fistula increases intraocular pressure by impeding venous return
4. intraorbital pathology: tumors
5. injury within the globe: retinal detachment, ocular trauma
6. unilateral vitreous hemorrhage: e.g. with SAH (Terson’s syndrome)