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Graefes Arch Clin Exp Ophthalmol (2013) 251:543547 DOI 10.1007/s00417-012-2082-9
CORNEA
In vitro effect of corneal collagen cross-linking on corneal hydration properties and stiffness
Georgios A. Kontadakis & Harilaos Ginis &
Nikolaos Karyotakis & Alexandros Pennos & Iro Pentari &
George D. Kymionis & Ioannis G. Pallikaris
Received: 6 December 2011 /Revised: 20 May 2012 /Accepted: 30 May 2012 /Published online: 23 June 2012 # Springer-Verlag 2012
AbstractBackground The purpose of this study is to evaluate in-vitro the immediate effect of corneal collagen cross-linking (CXL) on corneal hydration and stiffness.
Methods Forty-two corneal buttons from freshly enucleated porcine eyes were immersed in riboflavin 0.1% in dextran 20% dilution for 3 h in order for their hydration to reach equilibrium. Corneal buttons where divided into two groups; the first group was stored in dark conditions while the other group was irradiated with UVradiation (370 nm) for 30 min to simulate CXL according to the clinically applied protocol. After irradiation, all corneas were immersed in dextran 20% solution for 3 additional hours. Subsequently, each button underwent weighing, thickness measurement, and was mounted in a special device for the measurement of force versus deformation by compression. Finally, all corneal buttons were dehydrated for 48 h in a desiccating oven set at 62 C and weighed again to obtain their dry mass. Hydration (%) of each button was calculated.
Results Mean corneal hydration in the irradiated and the non-irradiated group of corneas was 69.8 and 72.2%, respectively (p<0.001). Differences in thickness and compressibility were not statistically significant. Thickness and hydration were positively correlated (Pearsons r00.714, p<0.001).
Conclusions CXL causes corneal dehydration that can be detected immediately after the procedure. This phenomenon may contribute to increased mechanical stiffness of the
cornea. A change in stiffness by means of compressibility could not be detected in porcine corneas.
Keywords Cornea . Corneal collagen cross-linking . Keratoconus . Corneal hydration
Introduction
Manipulation of the mechanical properties of the cornea is a major goal of corneal and refractive surgery [1]. It is currently understood that corneal biomechanics are involved in corneal ectatic disorders such as keratoconus, and as a risk factor for the development of iatrogenic post-LASIK ectasia [2, 3]. These disorders lead to progressive thinning and protrusion of the cornea, resulting in high irregular...