Title: Influence%20of%20UVA-Riboflavin%20corneal%20collagen%20cross-linking%20on%20biomechanical%20properties%20of%20keratoconic%20eyes
1Influence 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.
2Background
- 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.
3Background
- 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)
4Purpose
- To assess changes in biomechanical properties of
human corneas following treatment of keratoconus
with UVA-Riboflavin CXL
5Methods
- 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
6Methods
- 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
7Results
- 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.
8Results
9Results
10Results
11Discussion
- 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.
12Conclusions
- 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