Neuro-ophthalmology: Optic Atrophy

Question 1

Describe optic atrophy - what are the 3 hallmark features?

Answer 1

• Pale (chalky white) disc appearance w/ sharp margins
  o Due to damage to retinal GCs anywhere along the pathway (retina to lateral geniculate body (where they synapse))
• Damage to retinal ganglion cells at any level
• Lesion in optic pathway anterior to lateral geniculate body
  o Anterior to chiasm: unilateral optic atrophy
  o Posterior to chiasm: bilateral optic atrophy – due to fibres crossing
• 4-6 weeks to appear from time of axonal damage – 4-6 weeks for pallor to occur

Question 2

Describe examination of disc(s) with optic atrophy?

Answer 2

• Comparison of colour of 2 discs:
  o When look at one eye, need to remember this when go to look at other eye
  o May demonstrate subtle pallor when compare the discs
  o If px has unilateral pseudophakia (got an IOL) – can change appearance of colour of disc (& other structures)
• Evaluation of surface vasculature of disc:
  o Thin or absent capillary net (finer BVs seen on surface of disc) if have optic atrophy
   If ONH appears yellow then that tells you there is an absent/reduced capillary net because the yellowing is the thing that indicates it is not present
• Assessment of RNFL:
  o Dropout (break) in presence of RNFL may precede atrophy
  o Loss of normal translucent/glistening appearance – can be broad or fine patches
  o Most likely to occur superiorly & inferiorly first
  When look at RNFL that surrounds optic disc to assess it

Question 3

What are the causes of Priamry Optic Atrophy?

Answer 3

• Paleness of ONH with no adjacent swelling of ONH
• Causes:
  o Retrobulbar neuritis – inflammation/injury/demyelination behind ONH – ONH itself would not appear swollen just pale (4-6 weeks after initial insult to ONH)
  o Compression by tumour or aneurysm
  o Hereditary optic neuropathies – inherited, various subtypes
  o Toxic & nutritional optic neuropathy – px’s nutrition may be reduced or taken a substance that has caused a toxic response

Question 4

What is Secondary Optic Atrophy?

Answer 4

• Proceeded by swelling of ONH – if nerve head becomes swollen it ill become damaged, if it damages the nerves they’ll die off and that will cause optic atrophy 4-6 weeks later

Question 5

Describe the management of primary and secondary optic atrophy?

Answer 5

• Depends upon cause
  o Primary:
   Retrobulbar neuritis
• If it is demyelination & px has not been diagnosed w/ MS then refer them possibly via GP to get scans done
• If inflammation or injury – get investigated through a scan
   Compression by tumour or aneurysm
• Life threatening – aneurysms can cause problems at any moment in time – want to get them referred emergency or urgently
   Hereditary optic neuropathies
• Explore w/ px about family hx – much less urgent intervention – not much tx that can be done – wanting a diagnosis here to rule out other possible causes (would refer to ophthalmologist for that)
   Toxic & nutritional optic neuropathies
• Management depends on exact problem – if px is alcoholic or drug addict – want to talk to them about possible tx for that using GP – if think it is toxic due to meds they are taking then liaise with prescriber for that (could be cancer meds – needs careful thought process as obvs can’t stop cancer meds)
  o Secondary:
   Swelling of ONH
  “Optic Disc Pallor (suspected compressive lesion”  URGENT referral (not same day but within next week or so)
  “Unexplained loss of vision”, “papilloedema”, “CRAO”, “suspected temporal arteritis”  EMERGENCY SAME DAY referral
  Most likely management is that they are going to get to the hospital for scans