Date amended:
Statements of Principles
Current RMA Instruments:
Reasonable Hypothesis SOP
57 of 2016
Balance of Probabilities SOP
58 of 2016
SOP bulletin information on new Instruments:


ICD Coding:
  • ICD-9-CM Codes: 322.2
  • ICD-10-AM Codes: G03.1
Brief description

The optic chiasm is an X shaped structure at the base of the brain where the optic nerves from each eye come together and partly cross over.  Optochiasmatic arachnoiditis is a rare conidition in which there is chronic inflammation of the arachnoid layer (of the meninges) that covers the optic chiasm.  This condition results in local damage with scarring and progressive loss of vision.

Confirming the diagnosis

The diagnosis is difficult to establish.  It may be suspected based on the clinical presentation and imaging findings (MRI scan), but may require visual inspection of the area during surgery for confirmation.

The relevant medical specialist is an ophthalmologist or neurosurgeon.

Additional diagnoses covered by SOP

  • Nil
Conditions not covered by SOP
  • Optic neuritis#

# non-SOP condition

Clinical onset

Clinical onset will generally correspond with the time of confirmation of the diagnosis.  Backdating of onset before that time will be difficult due to the non-specificity of symptoms and clinical findings. 

Clinical worsening

The condition is difficult to treat and progression of symptoms is likely.  Establishing a clinical worsening beyond the normal course of the disease will be difficult and will require specialist opinion.