OPTIC DISC ASSESSMENT

     John Grigg
     Senior Lecturer
     Department of Ophthalmology, University of Sydney
     johng@eye.usyd.edu.au
 
Optic nerve Points to evaluate
 
  • Vertical cup-to-disc ratio
  • Colour and width of neuroretinal rim
  • Symmetry between eyes
  • Size of the optic disc
 
Optic nerve: Normal topography
     

  
  • Cup: small, pale
  • Neural rim: wide symmetrical orange-red
  • Retinal vessels: note position
 
Optic disc assessment
 
  • Jonas - characteristic configuration of horizontally oval cup in vertically oval disc is normal.
  • Rim with width greatest inferior > superior > nasal > temporal (ISNT rule)
    - If not ? Glaucoma
  • Vertically oval cup
  • Concentric enlargement of cup - if increase over time diagnostic
 
Pathological optic disc changes
 
  • Asymmetry of cups in both eyes > 0.2
  • Focal loss of neuroretinal rim /notch / acquired pit
  • Changes in vessels on optic disc: nasalisation, bayoneting, flyover vessels, focal narrowing of vessels, disc haemorrhage
 
Notching of disc
     

  
  • Inferior notching
 
Vascular changes on Disc in glaucoma
 
  • Nasalisation of vessels
  • Bayonetting of vessels
  • Baring of circumlinear vessel
 
Vascular changes on Disc in glaucoma
 
  • Nasalisation of vessels  

 
Vascular changes on Disc in glaucoma
 
  • Bayonetting of vessels  

 
Vascular changes on Disc in glaucoma
 
  • Baring of circumlinear vessel  

 
Pathological optic disc changes
 
  • Peripapillary atrophy:
    - Beta atrophy : increased in glaucoma, particularly where most neuroretinal rim loss
  • Nerve fibre layer changes:
    - grooves, wedge defects, diffuse loss
 
Pathological optic disc changes
 
  • Peripapillary atrophy:
    - Beta atrophy : increased in glaucoma, particularly where most neuroretinal rim loss  

 
Pathological optic disc changes
 
  • Nerve fibre layer changes:
    - grooves, wedge defects, diffuse loss  

 
Detecting progression
 
  • Disc changes may not be objective unless automated
    - (new technology, eg. Heidelberg Retinal Tomograph, Nerve Fibre Layer Analyser)
  • Visual field progression:
    - probability plots, mean deviation, pattern deviation, statpac (Beware short-term fluctuation)
    - Progressor
  • Objective perimetry:
    - Accumap
 
Optic nerve cross section
 
 
Cup/disc ratio 0.5
 
 
Cup/disc ratio 0.5 - other examples
 
 
Optic disc crescent
 
 
Disc margin haemorrhage
 
  • Cup/disc ratio 0.9  

 
Cup/disc ratio 0.85
 
 
Cup/disc ratio 0.9
 
 
Cup/disc ratio 0.8
 
  • Superior disc margin Haemorrhage  

 
Pathology of Optic Disc in Glaucoma
 
 
Red Free photo showing nerve fibre defects
 

    Note the nerve fibre layer arrangement and horizontal demarcation

 
Cup/disc ratio 0.9 - exposure lamina cribrosa
 
 
Prevalence of Open Angle Glaucoma in Australia: Blue Mountains Eye Study