Painful
Arteritic anterior ischemic optic neuropathy
Optic neuritis
Temporal arteritis†
Painless
Amaurosis fugax
Central retinal artery occlusion (CRAO)†
Central retinal vein occlusion (CRVO)†
High altitude retinopathy<unk> 
Posterior reversible encephalopathy syndrome (PRES)
Retinal detachment†
Stroke†
Vitreous hemorrhage
Traumatic optic neuropathy (although may have pain from the trauma)
Arteritic anterior ischemic optic neuropathy
Optic neuritis
Temporal arteritis†
Amaurosis fugax
Central retinal artery occlusion (CRAO)†
Central retinal vein occlusion (CRVO)†
High altitude retinopathy<unk> 
Posterior reversible encephalopathy syndrome (PRES)
Retinal detachment†
Stroke†
Vitreous hemorrhage
Traumatic optic neuropathy (although may have pain from the trauma)
†Emergent Diagnosis
Open-angle glaucoma
Painful
Acute angle-closure glaucoma
Arteritic anterior ischemic optic neuropathy
Traumatic optic neuropathy
Optic neuritis
Temporal arteritis†
Ocular foreign body