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Symptoms
- Visual impairment
- Central visual field loss
Findings
- 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!
Types
- 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
- Methanol poisoning as a classic example
- 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
- Dose-dependent
- Visual impairment, central/centrocecal scotoma, temporal disc pallor
- Ethambutol therapy as a classic example
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
Sources
- 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)