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Farhad Hafezi, Olivier Richoz; Corneal Collagen Cross-linking (CXL) Does Not Alter The Corneal Re-epithelialization Rate. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4189.
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Corneal collagen cross-linking (CXL) is a technique to arrest primary (keratoconus and pellucid marginal degeneration) and secondary (iatrogenic) keratectasia. CXL in patients suffering from Pellucid marginal degeneration(PMD) requires UVA irradiation close to the inferior limbus. Currently, there is controversy whether the limbal stem cells may suffer from UVA irradiation or not. Many surgeons cover the limbus and the peripheral cornea, which might compromise the therapeutic effect of CXL for PMD. We have tested the effect of CXL on the corneal limbus in an experimental setting.
We performed epi-off CXL in male New Zealand White Rabbits using 1) various irradiation areas (central cornea alone, whole cornea including the entirelimbus), 2) UVA light at 365 nm, 3) various intensities (3mW, 10mW) and 4) various irradiation durations (10 min, 30 min). The right eye was the treated eye and the left eye served as control. Investigations include light microscopy, immunohistochemistry, Western blotting and rt-PCR.
Preliminary data demonstrate an absence of thrombosis of limbic vessels and a complete re-epithelialization of the cornea within 48 hours, irrespective of UVA intensity and/or duration of irradiation. The rate of re-epithelialization is an indirect indicator for the regenerative capacity of limbal stem cells.
Direct irradiation of the corneal limbus does not affect the efficacy of corneal re-epithelialization. This might indicate that the limbal stem cells keep their regenerative capacity even when irradiated with UVA. CXL with eccentric irradiation for the treatment of PMD can be performed without shielding the corneal limbus.
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