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Marina Hovakimyan, Thomas Stahnke, Marc D Friedman, Oliver Stachs, Rudolf Guthoff; Morphological changes in the rabbit cornea after standard and accelerated cross-linking. Invest. Ophthalmol. Vis. Sci. 2016;57(12):No Pagination Specified.
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© ARVO (1962-2015); The Authors (2016-present)
Corneal cross-linking (CXL) protocols are still undergoing development in order to increase patients’ safety and comfort. Different accelerated protocols have been devised to shorten the procedure by increasing UVA irradiance, pulsing the light, and adding supplementary oxygen. In the present experimental study morphological changes after standard and accelerated CXL were monitored in vivo and ex vivo.
Twelve New Zealand White rabbits were divided into three groups (each N=4). Group I underwent CXL according to the Dresden protocol (continuous UVA light; 3 mW/cm2; 30 min). Group II was treated with a higher irradiance (30 mW/cm2; 4 min) in combination with 100 % oxygen. Group III was treated with the same protocol as group II with pulsed versus continuous UVA light. Morphological changes were monitored using in vivo confocal laser-scanning microscopy (CLSM) 3 days following CXL and once a week thereafter. Keratocyte damage was quantified as a surrogate parameter for CXL. Directly after sacrificing the animals optical coherence tomography (OCT) of the enucleated eyes was performed. Histological sections of fixed and embedded corneas were analyzed with DAPI staining.
Animals treated with modified protocols exhibited reduced cell damage compared to group I, in which we observed severe cell loss in the anterior and keratocytes activation in the posterior stroma. These changes were absent in animals treated with the modified CXL protocols. The acellular zone was 205 ± 34 µm in size after one week in group I. It was less pronounced in groups II and III, 113 ± 26 µm and 119 ± 53 µm, respectively. The thickness of the acellular zone decreased in all three groups over the course of 4 weeks. At this time all corneas were similar with regard to keratocyte distribution in the anterior and posterior stroma, which was confirmed by histology and OCT.
In recent years, CXL has gained considerable attention, not only as treatment for keratoconus but also as a preventative measure following LASIK procedures. Our study demonstrates that CXL with accelerated protocol modifications using pulsed light and the addition of oxygen causes less severe corneal damage than the Dresden protocol. In the future, such modifications of CXL protocols may allow for decreased treatment and procedure time increasing patients’ safety and comfort.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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