September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Cross-linking biomechanical effect in human corneas by same energy, different UV-A fluence: an enzymatic digestion comparative evaluation.
Author Affiliations & Notes
  • George Asimellis
    Kentucky College of Optometry, PikeVille, Kentucky, United States
    LaserVision.gr Clinical & Research Eye Institute, Athens, Greece
  • A. John Kanellopoulos
    LaserVision.gr Clinical & Research Eye Institute, Athens, Greece
    Ophthalmology, NY University, NY, New York, United States
  • Footnotes
    Commercial Relationships   George Asimellis, None; A. Kanellopoulos, Alcon (C), Allergan (C), Avedro (C), i-Optics (C), ISP Surgical (C), Keramed (C)
  • Footnotes
    Support  None
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 2382. doi:
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      George Asimellis, A. John Kanellopoulos; Cross-linking biomechanical effect in human corneas by same energy, different UV-A fluence: an enzymatic digestion comparative evaluation.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2382.

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      © 2017 Association for Research in Vision and Ophthalmology.

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Abstract

Purpose : Collagenase has been known to contribute to break-down of collagen in the corneal stroma. This breakdown is a vigorous biochemical process used as an indirect metric of corneal biomechanical properties. The stabilizing biochemical effect of corneal cross-linking (CXL) may be thus reflected by an increased resistance to collagenase digestion. Clinical results suggesting comparable effectiveness of Higher-fluence (irradiance) CXL variations to the conventional protocol (3 mW/cm2) in stabilizing keratoconus progression have been reported. The enzymatic degradation resistance modulations achieved via CXL application at different UV-A irradiances has not been studied in human corneas. The purpose of this study is to comparatively evaluate ex-vivo these enzymatic degradation resistance differences.

Methods : The study involved twenty-five human donor corneas, randomly allocated to 5 groups (n=5 each). CXL was applied with UV-A irradiance of 3-mW/cm2, 9-mW/cm2, 18-mW/cm2, 30-mW/cm2, and 45-mW/cm2, maintaining equal cumulative energy dose of 5.4 J/cm2. UV-A was delivered on half of the cornea. The non-irradiated halves served as controls. Specimens were subjected to collagenase-A enzymatic digestion. The time to complete dissolution in each specimen was recorded.

Results : Time to dissolution in group-A (3-mW/cm2 for 30’) was 321±13.4 minutes (range: 300 to 330) compared to 171±8.2 (range: 165 to 180) for their control. In group-B (9-mW/cm2 for 10’) 282±19.6 minutes (range: 270 to 315) compared to 177±6.7 (165 to 180) for their control. In group-C (18 mW/cm2 for 5’) 267±19.6 minutes (range: 240 to 285) compared to 177±7.7 (range 165 to 180) for their control. In group-D (30-mW/cm2 for 3‘) 252±12.5 minutes (range: 240 to 270) compared to 180±10.6 minutes (range: 165 to 195) for their control. In group-E (45-mW/cm2 for 2‘) 204±17.1 minutes (range: 180 to 225) compared to 186±8.2 minutes (range: 180 to 195) for their control.

Conclusions : The data in this ex-vivo human corneal study indicate that the biomechanical effect of CXL studied by resistance to enzymatic digestion in human corneas is comparable between irradiance of 9, 18 and 30-mW/cm2, and appears to be reduced at fluence of 45mW/cm2.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

Design and execution of the patterned half-area illumination of the treated corneas.

Design and execution of the patterned half-area illumination of the treated corneas.

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