Abstract
AimTo evaluate quantitatively the effects of the Epi-Off-CXL irradiance dose on the stromal stiffening of pig corneas.SettingLaboratory of Biological structures (LaBS), Politecnico di Milano, Milano, Italy.MethodsInflation tests have been carried on 90 excised and de-epithelized pig corneas, monitoring the change of configuration of the corneal dome at specific pressures. Test have been carried out twice on each cornea, once before and once after Epi-Off-CXL performed at a constant irradiance of 9 mW/cm2 and variable UV-A exposure times. Corneas were grouped according to the exposure time (2.5, 5, 10, 15 and 20 min), proportional to the irradiation dose (1.35, 2.7, 5.4, 8.1, and 10.8 J/cm2). A theoretical model based on linearized shell theory has been used to estimate the increment of the corneal stiffness.ResultsThe linearized shell theory allowed to establish a quantitative relation between the increment of the stiffness parameters and the irradiation dose. Relative to the pre-treatment values, in all experiments the post-treatment corneal stiffness revealed a pronounced increase. In general, the stiffness gain increased with the exposure time. No significant differences in stiffening was observed between tests conducted at 2.5, 5, and 10 min exposure.ConclusionsQualitatively, the effectiveness of accelerated CXL treatments observed in pig corneas complies very well with in-vivo clinical results in humans, suggesting that experimental data in pigs can be very useful for the design of the procedure in humans. A larger irradiation dose provides a larger increment of the corneal stiffness. Due to the biological variability of the tissues, however, it is difficult to distinguish quantitatively the level of the reinforcement induced by accelerated protocols (low doses with < = 10 min exposure), less prone to induce damage in the corneal tissue. Therefore, the definition of personalized treatments must be related to the actual biomechanics of the cornea.
Highlights
The cornea, the outermost tissue of the eye, provides mechanical protection to the inner parts of the eye
The effectiveness of accelerated CXL treatments observed in pig corneas complies very well with in-vivo clinical results in humans, suggesting that experimental data in pigs can be very useful for the design of the procedure in humans
Epi-Off-Crosslinking on porcine corneas provides a larger increment of the corneal stiffness
Summary
The cornea, the outermost tissue of the eye, provides mechanical protection to the inner parts of the eye. The stroma is composed by a matrix of elastin and proteoglycans embedding collagen fibrils, organized into a hierarchical architecture able to provide the necessary mechanical stiffness [4]. The spherical shape of the cornea, structurally a thin shell, is achieved by the response of the tissue to the action of the intraocular pressure (IOP) due to the internal fluids [6]. Keratoconus is a genetic progressive non inflammatory disease of the cornea distinguished by paracentral corneal thinning, decrease of crosslinks between collagen fibrils, and evident reduction of mechanical stiffness [7]. Keratoconus corneas are very compliant and lose the spherical shape in favor of a conical shape, impairing the focusing abilities of the eye
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
