April 2014
Volume 55, Issue 13
Free
ARVO Annual Meeting Abstract  |   April 2014
Optic Nerve Sheath Mechanics and Permeability in VIIP Syndrome
Author Affiliations & Notes
  • Julia Raykin
    Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, GA
  • Lauren Best
    NASA Glenn Research Center, Cleveland, OH
  • Rudy Gleason
    Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, GA
  • Lealem Mulugeta
    Universities Space Research Association, Houston, TX
  • Jerry Myers
    NASA Glenn Research Center, Cleveland, OH
  • Emily Nelson
    NASA Glenn Research Center, Cleveland, OH
  • Brian C Samuels
    Department of Ophthalmology, U. Alabama at Birmingham, Birmingham, AL
  • C Ross Ethier
    Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, GA
  • Footnotes
    Commercial Relationships Julia Raykin, None; Lauren Best, None; Rudy Gleason, None; Lealem Mulugeta, None; Jerry Myers, None; Emily Nelson, None; Brian Samuels, None; C Ethier, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science April 2014, Vol.55, 4591. doi:
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      Julia Raykin, Lauren Best, Rudy Gleason, Lealem Mulugeta, Jerry Myers, Emily Nelson, Brian C Samuels, C Ross Ethier; Optic Nerve Sheath Mechanics and Permeability in VIIP Syndrome. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4591.

      Download citation file:


      © ARVO (1962-2015); The Authors (2016-present)

      ×
  • Supplements
Abstract
 
Purpose
 

To investigate the biomechanical properties of the optic nerve sheath (i.e. fluid permeation across the meninges and tissue stiffness) at various CSF pressures. Such information is relevant to understanding ophthalmic changes associated with long-duration space flight (i.e. Visual Impairment and Intracranial Pressure syndrome; VIIP), thought to be largely due to cephalad fluid shifts causing altered ocular, cardiovascular, lymphatic and cerebrospinal fluid (CSF) pressures. The hypothesis is that increased CSF pressure drives connective tissue remodeling of the posterior eye and optic nerve sheath.

 
Methods
 

The meninges of fresh porcine eyes (n=10) was reflected to expose the optic nerve, which was truncated 3-4 mm posterior to the sclera. The meninges were repositioned leaving a “hollow” cylinder of connective tissue attached to the posterior sclera. The distal end was cannulated, sealed, and attached to a pressure control system that simulated CSF pressure changes. The anterior chamber of the eye was also cannulated for independent control of intraocular pressure (IOP). While IOP remained stable, a CCD camera recorded the meningeal diameter as the CSF pressure cycled between 7-50 mmHg. In a second set of experiments, the rate of fluid permeation across the meninges was recorded by observing the drainage of an elevated fluid reservoir connected to the meninges.

 
Results
 

Cyclic pressure-diameter curves showed a preconditioning effect, with repeatable behavior in cycles 4-6 (Figure). The meninges showed marked nonlinear stiffening, particularly at CSF pressures >15 mmHg. The tangent moduli extracted from these data were 318, 745, and 1273 kPa at CSF pressures of 7, 15 and 30 mmHg, respectively. Permeability experiments determined a flow rate of ~2ml/hr through the intact meninges at a driving pressure of 30mmHg, corresponding to a permeability of 7.34x10-5 ml/min/cm2/mmHg.

 
Conclusions
 

The meninges demonstrate biomechanical properties typical of other soft tissues, with nonlinear stiffening and appreciable hysteresis on pressure cycling. This tissue is surprisingly permeable, suggesting that there could be important CSF drainage through the meninges into the periorbital fat. These experimental measurements, extended to cadaveric eyes, will be critical in informing computational models aimed at identifying the pathophysiology of VIIP syndrome.

 
 
Pressure-diameter curves for a single eye, tested over six 7-50 mmHg pressure cycles.
 
Pressure-diameter curves for a single eye, tested over six 7-50 mmHg pressure cycles.
 
Keywords: 629 optic nerve • 519 extracellular matrix • 631 orbit  
×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×