Optic Atrophy

When is it optic atrophy?

The optic nerve comprises of 1.2 million myelinated axons. Once damaged, the axons do not regenerate (behaves more like a white matter tract than a true peripheral nerve). Thus optic atrophy is the common morphological endpoint of any optic neuropathy. Clinically, the neuro-retinal rim of the optic disc (the area excluding the cup) appears pale/yellow, with associated visual impairment. This is different to glaucoma, where the disease is characterized by an increased cup to disc ratio but the neuro-retinal rim remains pink. Optic atrophy is a clinical diagnosis and does not carry any implications on the underlying cause.

Causes of optic atrophy:

  • Compressive optic neuropathy (papilloedema, tumors, thyroid eye disease)
  • Ischaemic optic neuropathy (arteritic or non-arteritic, diabetes)
  • Optic neuritis (infectious or inflammatory)
  • Nutritional Deficiencies (vitamin B12 and folate deficiencies)
  • Toxic optic neuropathy (ethambutol toxicity, common in Hong Kong due to pulmonary tuberculosis being endemic in this locality)
  • Infiltrative diseases (leukemia, sarcoidosis)
  • Hereditary opic neuropathies (autosomal dominant, mitochondrial)
  • Iatrogenic – Radiation optic neuropathies (common in Hong Kong, due a high incidence of nasopharyngeal carcinoma, and the primary treatment being radiotherapy)
  • Traumatic
  • Glaucomatous optic neuropathy / glaucoma – optic atrophy in end-stage disease

Workup considerations of optic atrophy to dertermine the underlying cause:

  • Medical and family history
  • Visual acuity
  • Intraocular pressure
  • Pupillary reflexes
  • Colour vision
  • Visual field testing
  • Neuroimaging
  • Blood tests (vitamin B12, folate, VDRL, ANA)

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