June 2013
Volume 54, Issue 15
Free
ARVO Annual Meeting Abstract  |   June 2013
Corneal geometric stress factor to evaluate response to corneal collagen cross-linking in keratoconus
Author Affiliations & Notes
  • Riccardo Vinciguerra
    Opthalmology, Humanitas Clinical and Research Center, Milan, Italy
    Dept. of Surgical and Morphological Sciences, University of Insubria, Circolo Hospital, Varese, Italy
  • Cynthia Roberts
    Ophthalmology and Biomedical Engineering, The Ohio State University, Columbus, OH
  • Ashraf Mahmoud
    Ophthalmology and Biomedical Engineering, The Ohio State University, Columbus, OH
  • Claudio Azzolini
    Dept. of Surgical and Morphological Sciences, University of Insubria, Circolo Hospital, Varese, Italy
  • Paolo Vinciguerra
    Opthalmology, Humanitas Clinical and Research Center, Milan, Italy
  • Footnotes
    Commercial Relationships Riccardo Vinciguerra, None; Cynthia Roberts, Oculus Optikgerate GmbH (C), Ziemer Ophthalmic Systems AG (C), Sooft Italia (R), Carl Zeiss Meditec (F); Ashraf Mahmoud, None; Claudio Azzolini, None; Paolo Vinciguerra, SOOFT Italia (C), Oculus Optikgerate GmbH (C), NIDEK, Japan (C), Schwind (C)
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2013, Vol.54, 1621. doi:
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to Subscribers Only
      Sign In or Create an Account ×
    • Get Citation

      Riccardo Vinciguerra, Cynthia Roberts, Ashraf Mahmoud, Claudio Azzolini, Paolo Vinciguerra; Corneal geometric stress factor to evaluate response to corneal collagen cross-linking in keratoconus. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1621.

      Download citation file:


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

      ×
  • Supplements
Abstract
 
Purpose
 

To evaluate corneal stress distribution based purely on geometry without consideration of loading via intraocular pressure, pre and post corneal collagen cross-linking (CXL) with a new tomographic parameter, “Corneal Geometric Stress Factor”.

 
Methods
 

Tomographic data from four hundred and eighty subjects (323 right eyes and 340 left eyes) were collected retrospectively from Istituto Clinico Humanitas (Rozzano, Italy) with up to 70 months pre-CXL and 60 months post-CXL. Pentacam U12 files (Oculus Optikgerate GmbH, Wetzlar, Germany) were transferred to The Ohio State University and processed independently using custom software. Corneal Geometric Stress Factor (CGSF) was calculated at corresponding points from curvature and pachymetric maps to create a CGSF map. CGSF evaluates the cornea’s contribution to Hoop stress without considering the applied load (intraocular pressure) and it can be expressed as the radius of curvature over twice of the thickness (CGSF=R/2t). Cone Location and Magnitude Index (CLMI) and Flat zone Location and Magnitude Index (FLMI) were applied to the CGSF map to obtain maximum stress and minimum stress and to calculate the level of asymmetry in the stress pattern. Pre and post CXL regression analyses were performed.

 
Results
 

Regression analysis showed a significant (p<0.0001) positive correlation of asymmetry stress distribution before CXL demonstrating increasing asymmetry in the stress pattern, and a significant negative correlation after CXL (p=0.0001) demonstrating a pattern of reducing asymmetry over time. Maximum and minimum stress factors similarly had positive correlation before CXL (p<0.0001), indicating increasing stress over time and negative correlation after CXL (p<0.0001), indicating decreasing stress over time.

 
Conclusions
 

Biomechanical analysis shows CXL is able not only to stop the progression of the disease, but even to reverse the cycle of biomechanical decompensation of keratoconic corneas. These findings can be explained by the fact that the decrease of thickness and curvature associated with CXL treatment induces a consequent reduction in both minimum and maximum stress as well as a reduction of asymmetry in the stress distribution. IOP can modify the stress magnitude, but not change the pattern demonstrated.

 
Keywords: 574 keratoconus • 479 cornea: clinical science  
×
×

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.

×