Influence%20of%20UVA-Riboflavin%20corneal%20collagen%20cross-linking%20on%20biomechanical%20properties%20of%20keratoconic%20eyes

1
Influence of UVA-Riboflavin corneal collagen
cross-linking on biomechanical properties of
keratoconic eyes

• David Zadok MD, Yakov Goldich MD,
• Yaniv Barkana MD, Adi Rasko MD, Isaac Avni MD
• Department of Ophthalmology
• Assaf Harofeh Medical Center
• Israel

The authors have no conflicts of interest and no
financial interest in the articles subject
matter or methods mentioned.
2
Background

• Corneal Collagen-Cross linking (CXL) using UVA
  and Riboflavin was proposed recently as treatment
  to stop progression of keratoconus1
• A suggested mechanism is stiffening of the
  cornea2

1.Wollensak G. et al, Riboflavin/ultraviolet-a-ind
uced collagen crosslinking for the treatment of
keratoconus. Am J Ophthalmol. 2003
May135(5)620-7. 2.Kohlhaas M. et al,
Biomechanical evidence of the distribution of
cross-links in corneas treated with riboflavin
and ultraviolet A light. J Cataract Refract Surg.
2006 Feb32(2)279-83.
3
Background

• The Ocular Response Analyzer (ORA Reichert Inc)
  provides in vivo measurements of corneal
  biomechanical properties, namely corneal
  hysteresis (CH) and corneal resistance factor
  (CRF), and non contact measurements of IOP
  Goldmann correlated IOP (IOPg) and corneal
  compensated IOP (IOPcc)

4
Purpose

• To assess changes in biomechanical properties of
  human corneas following treatment of keratoconus
  with UVA-Riboflavin CXL

5
Methods

• Ten eyes of 10 patients aged 26.55.7 years were
  treated with CXL and assessed with the ORA
• Inclusion criteria
• progressive keratoconus documented clinically (
  Astigmatic refraction and/or topography) within
  the past 12 months
• Age gt18 years
• Absence of corneal opacities
• No previous ocular surgeries
• Minimum corneal thickness gt 400 µm
• No wearing of rigid contact lenses for 1 month
  before initial evaluation

6
Methods

• Treatment corneal deepithelization, instillation
  of 0.1 riboflavin in 20 dextran solution every
  5 minutes for 40 minutes and corneal irradiation
  with UVA 3 mW/cm2 for 30 minutes
• Patients were assessed before, 1week, 1month and
  3 months after treatment. Comparison of
  postoperative to preoperative measurements was
  done

7
Results

• CH and CRF were transiently elevated after
  cross-linking treatment, without statistical
  significance.
• IOPcc and IOPg were statistically significantly
  higher at 1 week and 1 month.
• The results presented in table and box and
  whisker plots (smallest, median and largest
  values with interquartile range) showing values
  before treatment (Preop) and on 1 week, 1 month
  and 3 months thereafter.

8
Results
9
Results
10
Results

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Discussion

• Previous in vitro studies showed increased
  corneal rigidity after CXL treatment using
  biomechanical stress-strain measurements3
• In this study there were no significant changes
  in biomechanical properties of human corneas as
  measured in vivo by ORA following CXL treatment.
  CH and CRF were transiently elevated 1 week after
  treatment, but without statistical significance
• IOPcc and IOPg were statistically significantly
  higher at 1 week and 1 month
• ORA-measured IOP changes may be a measurement
  artifact following changes in ocular
  characteristics (like increased corneal
  thickness), and not a real IOP elevation .

3.Wollensak G. et al, Stress-strain measurements
of human and porcine corneas after
riboflavin-ultraviolet-A-induced cross-linking. J
Cataract Refract Surg. 2003 Sep29(9)1780-5.
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Conclusions

• There were no differences in corneal
  biomechanical properties as measured with the
  Ocular Response Analyzer following corneal
  collagen cross-linking in keratoconus

Correspondence David Zadok MD email
dzadok_at_yahoo.com