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Br J Ophthalmol 2006;90:778-783 doi:10.1136/bjo.2005.086538
  • Laboratory science - Extended reports

Computer modelling study of the mechanism of optic nerve injury in blunt trauma

  1. S Cirovic1,
  2. R M Bhola2,
  3. D R Hose3,
  4. I C Howard1,
  5. P V Lawford3,
  6. J E Marr2,
  7. M A Parsons4
  1. 1Department of Mechanical Engineering, the University of Sheffield, Mappin Street, Sheffield S1 3JD, UK
  2. 2Academic Unit of Ophthalmology and Orthoptics, the University of Sheffield, Royal Hallamshire Hospital, Sheffield S10 2JF, UK
  3. 3Academic Unit of Medical Physics and Clinical Engineering, the University of Sheffield, I-Floor, Royal Hallamshire Hospital, Sheffield S10 2JF, UK
  4. 4Ophthalmic Sciences Unit, Academic Unit of Ophthalmology and Orthoptics, the University of Sheffield, Royal Hallamshire Hospital, Sheffield S10 2JF, UK
  1. Correspondence to: Dr M A Parsons Ophthalmic Sciences Unit, Academic Unit of Ophthalmology and Orthoptics, Royal Hallamshire Hospital, Sheffield S10 2JF, UK; a.parsons{at}sheffield.ac.uk
  • Accepted 3 January 2006
  • Published Online First 18 January 2006

Abstract

Aim: The potential causes of the optic nerve injury as a result of blunt object trauma, were investigated using a computer model.

Methods: A finite element model of the eye, the optic nerve, and the orbit with its content was constructed to simulate blunt object trauma. We used a model of the first phalanx of the index finger to represent the blunt body. The trauma was simulated by impacting the blunt body at the surface between the globe and the orbital wall at velocities between 2–5 m/s, and allowing it to penetrate 4–10 mm below the orbital rim.

Results: The impact caused rotations of the globe of up to 5000°/s, lateral velocities of up to 1 m/s, and intraocular pressures (IOP) of over 300 mm Hg. The main stress concentration was observed at the insertion of the nerve into the sclera, at the side opposite to the impact.

Conclusions: The results suggest that the most likely mechanisms of injury are rapid rotation and lateral translation of the globe, as well as a dramatic rise in the IOP. The strains calculated in the study should be sufficiently high to cause axonal damage and even the avulsion of the nerve. Finite element computer modelling has therefore provided important insights into a clinical scenario that cannot be replicated in human or animal experiments.

Footnotes

  • Competing interest statement: There are no competing interests to be declared.

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