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S. C. Kaufman, J. Dhaliwal; Cornea Collagen Cross-Linking and Keratocyte Apoptosis: A Confocal, Electron and Light Microscopy Study. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3912. doi: https://doi.org/.
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Corneal cross-linking is a novel technique that has the potential to halt the progression of corneal ectasias, such as keratoconus. Ultraviolet A light of 370 nm wavelength is used to produce a reaction that results in collagen cross-linking. This wavelength of UVA light has been shown to damage tissue. The purpose of this study is to evaluate morphological changes of keratocytes, undergoing cross-linking, using confocal, electron and light microscopy.
The central epithelium was partially removed from ex vivo eye bank corneas. Riboflavin 0.1% solution was applied every 2 minutes for 30 minutes, while the corneas were exposed to UV-A light at a wavelength of 370 nm and intensity of 3 mW/cm2. Each cornea was evaluated, using confocal, electron and histological microscopy.
Less than 2 hours after treatment, a superficial layer of highly reflective, spherical objects (4-10 µm) were observed. Many of these hyper-reflective spheres appeared up to a depth of 300 microns. The remainder of the corneal stroma and endothelium appeared normal. Within the anterior 300 µm, especially within the anterior 100 µm of the corneal stroma, electron microscopy demonstrated substantial keratocyte cell damage. The cell bodies exhibited considerable cell shrinkage and apoptosis. No observable pathologic changes were seen with light microscopy.
Although corneal cross-linking is a promising treatment that may halt ectatic corneal disease progression, the long-term clinical importance of our observed keratocyte loss is not clear. We believe that additional studies are warranted.
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