Ethiology Unilateral or bilateral Onset Opticnerve head Differential features Inflammatory neuropathy (ON) Unilateral (youngadults) Bilateral (children*, NMO*) Acuteorsubacute Edema (onethird of typical ON in youngadults); children* Normal (twothirds of typical ON) Young femails*; moderatevisionloss, spontaneoslyrecovering, painfullwitheyemovements#; central scotoma*; hyperintensity and enhancement of theopticnerve in MRI NMO Bilateral*; sequential to the fellow eye Acuteorsubacute Diffuse edema withouthemorrhages* Severevisionloss*;painfulleye*, unresponsivetosteroids; TM; AQP4 positive*, normal brain MRI* CRION Unilateral Acuteorsubacute Diffuse edema withouthemorrhages* Responsivetosteroidsbutrelapsingcourse; normal brain and spinal MRI; AQP4 negative*; autoinmmunelaboratory test negative* AAION Unilateral; rapidly sequential to the fellow eye without steroid treatment Acute Edema, RNFL hemorrhage*; chronicphase: pallorwithenlargement of the cup* Elderlypatients (>65 yearsold*), severevisionloss*, painfulleye*, prodromic and systemicsymptoms*; ESR and RCP elevated NAION Unilateral; felloweyeoften show the “disc at risk” Acute Sectorial edema*, RNFL hemorrhage*, peripapillary telangiectasia*, vessels attenuation*; chronic phase: pallor Elderlypatients (>50 yearsold), cardiovascular riskfactors (arterial hypertension, diabetes, dyslipemia),obstructivesleep apnea, altitudinal escotoma*, morningpresentation* Compresive Unilateral or bilateral Acute; subacute;chronic Normal; pallor; edema Imaging test (CT, MRI); cancerhistory; unresponsivetosteroids* Infiltrative Unilateral or bilateral Acute; subacute;chronic* Normal; pallor; edema Imaging test (CT, MRI); LP; cancerhistory*, unresponsivetosteroids*; systemicillness* Sarcoidosis Unilateral or bilateral Acute; subacute;chronic Normal; pallor; edema Young afroamericanfemales; systemicsymptoms (cough, erythemanodosum); opticneuropathy can resultfrom ON, granuloma (infiltrative), posterior uveítisor ICH Paraneoplasic Bilateral* Acute; subacute; chronic Normal; pallor; edema Known/ prior cancer; positive anti-CRMP-5 IgG SLE; Vasculitis Unilateral or bilateral Acute; subacute; chronic Normal*; pallor; edema* Systemicfeatures (respiratorysymptoms, jointpain, drymouth/dryeyes, skinlesions); positive biopsy; positive autoinmune laboratoytests Autoinmmune Unilateral or bilateral Acute; subacute; chronic Normal*; pallor; edema* Autoinmmunelaboratoy test positive butunspecific (ANA, RF etc) Normal brain and spinal MRI; cutaneusbiopsy compatible withcolagenousdiseaseor vasculitis Infectious Unilateral or bilateral Acute*; subacute; chronic Normal*; pallor; edema* Sexual exposure (syphilis, VIH); thickexposure (Lymedisease); Cat/Kittenexposure, macular exudates (Bartonella); inmmunosuppression Hereditary Bilateral (Leber: unilateral or rapidly sequential) Chronic* (Leber: acuteor subacute) Pallor (Leber: pseudoedema, telangiectasias) Familiaryhistory; central scotoma (Leber: young males, specificmutations) Nutritional/ toxic Bilateral Chronic (metanol: acuteor subacute) Normal; pallor (metanol: edema) Toxicexposure; B12 vitamindeficit; central scotoma Traumatic Unilateral or bilateral Acute Normal; edema; optic nerve avulsion History of head trauma ICH Bilateral (unilateral: Foster Kennedy syndrome) Chronic Edema ICP increased; idiopathic ICH (youngfemales, weightgain)

ON: Optic Neuritis; * Most Common; NMO: Neuromyelitis Optica; #: Typical ON; AAION: Arteritic Ischemic Optic Neuropathy; RNFL: Retinal Nerve Fiber Layer; ESR: Erythrocyte Sedimentation Rate; RCP: Reactive C Protein; NAION: Non Arteritic Ischemic Optic Neuropathy; CT: Computed Tomography; MRI: Magnetic Resonance Imaging; TM: Transverse Mielitis; AQP4 Igg: Aquoporine 4 Inmmunoglobuline G; CRION: Chronic Relapsing Inflammatory Optic Neuritis; LP: Lumbar Puncture; ICH: Intracraneal Hypertension; Anti- CRMP-5 Igg: Antibodies Against Collapsing Response-Mediator Protein-5; SLE: Systemic Lupus Erythematosus; ICP: Intracraneal Presssure

Table 1: Common features of optic neuropathies.