Neuro-ophthalmology: Appearance of Raised Optic Disc

Question 1

Describe optic disc drusen?

Answer 1

• Calcified nodules within ONH
• Affect 0.34% - 2% of population
• Bilateral in 75% - may be asymmetric
• Unclear pathophysiology – may be due to impaired GC axonal transport (may be in development) – debris from axon flow and deposited in ONH
• Buried in childhood, become more prominent (&forward in eye) w/ age
• Symptoms:
  o Most pxs asymptomatic – unless affects the bundle of nerves that go towards macula
• Examination:
  o Visual Fields:
   VF loss in 75-87%
   Enlarged blind spot – as drusen sitting in ONH push the nerves away a little bit
   Arcuate defect
   Generally, respect horizontal midline – altitudinal
• If affects superior fibres in retina then will get inferior VF defect
• If something affects whole disc but doesn’t kill all the fibres and there’s just some swelling – might get a generalised depression as all of VF is affected
   Remains stable or v slowly progresses
  o RAPD: possible if monocular/asymmetric – if affects enough of the fibres to affect the overall info about light level going from eye to brain
  o Optic Disc:
   Appears small in diameter – if drusen are pushing things inwards
   Anomalous branching vascular patterns – drusen pushing BVs out the way
   Round, whitish, yellow refractile bodies – describe their size (disc diameters) & location (clockface) – draw a picture
   Disc may be pale/atrophy/RNFL loss
• Treatment: None – tell px they’ve got them and if causes problems in future then they should come back

Question 2

Describe buried drusen vs swollen disc?

Answer 2

o Both may elevate the disc and blur its margins
o Optic disc drusen:
 Lack of hyperaemia
 Lack of microvascular changes – no telangiectasia
 Normal / atrophic (if damaged) nerve fibre layer
 Anomalous retinal vascular patterns – because BVs getting dispersed by drusen
o B-scan
o Fluorescein angiography
o MRI

Question 3

How will drusen appear on OCT vs oedema?

Answer 3

Drusen appears as small humps on OCT
Oedema appears a large hill – all elevated up

Question 4

Describe tilted optic disc?

Answer 4

• 1-2% of population
• 80% bilateral – if px has bilateral myopia
  o If px has anisometropia and one eye is myopic
• Congenital or associated w/ myopia
  o Eye grows – too long – anatomy at disc can change
  o Congenital – during development, optic nerve
  can insert slightly tilted
• Oblique insertion of optic nerve
• Normal vision – just an observation – most often does not affect macular fibres
• Examination:
  o Disc appearance:
   Oval, tilted appearance
   Can make it difficult to determine C:D
   Inferior peripapillary atrophy
  o Visual Field:
   Bitemporal loss – associated with atrophy (which is more common in congenital type than myopic type)
• V high myopia can be associated with atrophy
   Superior arcuate scotoma

Question 5

Describe myelinated nerve fibres?

Answer 5

• 1% of population
• Nerve fibres are myelinated within optic nerve & myelin sheath usually stops at lamina cribosa
• During development – sometimes the myelin can protrude into the ONH
• Incidental finding so tends to be unilateral
  o Unilateral in 80%
• Symptoms:
  o Usually asymptomatic
• Signs:
  o Fundus examination:
   Visible yellow patch of myelin around nerve head
  o Visual Fields:
   Enlarged blind spot is corresponding to area of myelin – covers photoreceptors so light cannot reach them

Question 6

Describe hypermetropic crowded disc?

Answer 6

• If really small disc in a hyperope (small eye relative to the optics) – it can look crowded
• When look at BVs – they look crowded or dilated
• Disc appears swollen or unusual but it is in fact normal

Question 7

List the types of intraocular disease that may give the appearance of raised and swollen disc?

Answer 7

• CRVO
• Posterior uveitis
• Posterior scleritis
• Hypotony