Other Optic Neuropathies

Nutritional & Toxic Optic Neuropathies - Vision Villains

• 📌 Mnemonic: "TEAM Villains": Tobacco/Alcohol, Ethambutol, Amiodarone, Methanol, Vitamin deficiencies.

⭐ Methanol poisoning classically causes optic disc hyperemia initially, followed by optic atrophy, and treatment involves fomepizole or ethanol.

Hereditary Optic Neuropathies - Gene-Sighted Woes

⭐ Leber Hereditary Optic Neuropathy (LHON) is characterized by maternal inheritance due to mitochondrial DNA mutations, typically affecting young males with acute/subacute painless bilateral vision loss.

• Leber Hereditary Optic Neuropathy (LHON)
  • 📌 Mnemonic: Lads, Hereditary, Optic Neuropathy, Mothers (Maternal inheritance).
  • Inheritance: Maternal (mtDNA mutations, e.g., 11778, 3460, 14484).
  • Onset: 15-35 years, acute/subacute painless bilateral vision loss (sequential or simultaneous).
  • Clinical: Central/cecocentral scotoma, ↓ color vision. Initially, peripapillary telangiectasia, disc hyperemia; later, optic atrophy.
  • Associated: Cardiac arrhythmias (e.g., Wolff-Parkinson-White syndrome), skeletal abnormalities.
• Dominant Optic Atrophy (DOA) - Kjer type
  • Inheritance: Autosomal Dominant (OPA1 gene mutation).
  • Onset: Insidious, childhood (4-6 years).
  • Clinical: Slowly progressive, bilateral, often asymmetric vision loss. Centrocecal scotoma, blue-yellow color defect (tritanopia). Temporal optic disc pallor.

Compressive & Infiltrative Optic Neuropathies - Pressure Points

• Optic Nerve Glioma:
  • Typically children, strong NF1 association.
  • Painless proptosis, ↓ vision.
  • MRI: Fusiform enlargement of optic nerve.
  • Mgmt: Observation, chemotherapy if progressive.
• Optic Nerve Sheath Meningioma (ONSM):
  • Primarily middle-aged women.
  • MRI: "Tram-track" sign (calcification, enhancement around nerve).
  • Mgmt: Observation, radiotherapy, surgery for severe cases.

  ⭐ Optic nerve sheath meningiomas classically present with the triad of painless progressive vision loss, optic atrophy, and optociliary shunt vessels (though shunt vessels are not always present).

• Thyroid Eye Disease (TED):
  • Most common cause of unilateral/bilateral proptosis in adults.
  • Diplopia, exposure keratopathy, compressive optic neuropathy.
  • CT/MRI: Enlarged extraocular muscles (sparing tendons).
  • Mgmt (optic neuropathy): IV methylprednisolone, orbital radiotherapy, surgical decompression.
• Infiltrative Optic Neuropathies (e.g., Sarcoidosis, Lymphoma):
  • Sarcoidosis: Optic disc granuloma, uveitis, ↑ACE.
  • Lymphoma: Older patients, often bilateral, masquerade syndrome.
  • MRI: Optic nerve thickening, enhancement.
  • Mgmt: Systemic steroids (sarcoidosis); chemotherapy/radiotherapy (lymphoma).

Traumatic Optic Neuropathy - Impact Insights

• Classification:

  • Direct TON: Penetrating injury, foreign body, direct nerve trauma.
  • Indirect TON: More common; blunt head trauma (e.g., frontal impact). Forces transmitted to optic canal.

• Pathophysiology (Indirect): Shearing forces on nerve fibers, vascular compromise (ischemia), edema within the unyielding optic canal.

• Clinical Presentation: Acute, often severe, unilateral vision loss; Relative Afferent Pupillary Defect (RAPD) prominent; dyschromatopsia, visual field defects.

• Immediate Assessment: Visual acuity, pupillary reactions, fundoscopy (may be normal initially), high-resolution CT scan (thin cuts of optic canal for fractures).

• Management (Indirect TON): Highly controversial; evidence for any intervention is limited.

• Options include observation, high-dose corticosteroids, or surgical optic nerve decompression. Decision is individualized.

⭐ The use of high-dose corticosteroids in indirect Traumatic Optic Neuropathy (TON) is controversial and not universally recommended; management decisions are often individualized based on presentation and timing.

High‑Yield Points - ⚡ Biggest Takeaways

• Nutritional/Toxic Optic Neuropathies: Cause bilateral, painless, progressive vision loss with central/cecocentral scotomas.
• Ethambutol toxicity: Dose-dependent, red-green dyschromatopsia.
• Methanol poisoning: Optic disc hyperemia then atrophy; formic acid is toxic.
• LHON: Mitochondrial inheritance, affects young males, acute severe bilateral vision loss.
• DOA: Autosomal dominant (OPA1), childhood onset, temporal pallor, blue-yellow color defect.
• Traumatic Optic Neuropathy: Indirect injury common, acute vision loss post-trauma.
• Amiodarone can cause insidious, bilateral optic neuropathy with prolonged disc swelling.