Toxic Optic Neuropathy

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  • Visual impairment
  • Central visual field loss


  • Typically bilateral and symmetric, painless
  • Visual impairment
  • Central scotoma / centrocecal scotoma
    • the maculopapillary bundle is initially affected
  • Initially normal optic nerve, later temporal pallor (due to maculopapillary bundle)
  • Temporal thinning of retinal nerve fiber bundles in OCT
  • No relative afferent pupillary defect (RAPD) due to bilateral/symmetric involvement
  • Impaired color vision
    • CAUTION: Blue-yellow color deficiencies may not be detected by Ishihara!


  • Acute
    • Methanol poisoning as a classic example
      • Typically from adulterated alcohol
    • Visual impairment, central/centrocecal scotoma, optic disc swelling
    • Metabolic acidosis
    • Treatment:
      • Fomepizole or alternatively ethanol
      • Dialysis
  • Chronic
    • Ethambutol therapy as a classic example
      • Dose-dependent
        • 15mg/kg body weight – low risk
        • 25-30mg/kg body weight: 6-10% risk of optic neuropathy
      • Monthly follow-ups with visual function testing necessary in case of reduced kidney function
    • Visual impairment, central/centrocecal scotoma, temporal disc pallor

Most common Causes

  • Alcohols: commercial alcohol, methanol, ethylene glycol
  • Antibiotics: Chloramphenicol, Sulfonamides, Linezolid
  • Antimalarials: Hydroxychloroquine, Chloroquine, Quinine
  • Tuberculostatics: Isoniazid, Ethambutol, Streptomycin
  • Antiarrhythmics: Digitalis, Amiodarone
  • Cancer drugs: Vincristine, Methotrexate, Tamoxifen
  • PDE Inhibitor: Sildenafil
  • Heavy metals: Lead, Mercury, Thallium
  • Others: Carbon monoxide, Tobacco


  • EyeWiki Toxic Optic Neuropathy
  • Toxic optic neuropathy von Dr. Andrew G. Lee
  • Sharma P, Sharma R. Toxic optic neuropathy. Indian J Ophthalmol. 2011;59(2):137‐141. doi:10.4103/0301-4738.77035
  • The Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease; Nika Bagheri MD, Brynn Wajda MD, et al; Lippincott Williams&Wilkins; 7th Edition (2016)
  • Kanski’s Clinical Ophthalmology: A Systematic Approach; Jack J. Kanski MD, Brad Bowling MD; Saunders Ltd.; 8th Edition (2015)