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)
