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G. E. Noguera, J. Castro-Combs, W. Camacho, S. A. R. Martins, G. G. Quinto, P. Wittmann, A. Behrens; Corneal Epithelial Removal Effects on Corneal Biomechanics After Riboflavin-UVA Corneal Collagen Cross-Linking. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5479.
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Corneal abrasion previous to corneal collagen cross-linking (UV CCL) is a painful procedure that exposes the cornea to potential risks such as infections and scar formation that could lead to a decrease in corneal transparency. The purpose of this study was to evaluate the effects of an intact epithelium layer in corneal biomechanical changes after UV CCL.
20 New Zealand white rabbits were randomly divided in 2 treatment groups: Group A (n=10) was exposed to UVA-light (370 nm) and riboflavin 0.1 % for 30 min, and group B (n=10) was exposed to the same treatment after epithelium debridement. Central Corneal thickness (CCT), corneal hysteresis (CH), and corneal resistance factor (CRF) were measured weekly for 3 weeks. Six corneas (n=3 per group) were used for histology to determine keratocyte cell density in the superficial medial and deep corneal stroma.
Three weeks after UV CCL, CH increased 14.3%in group A and 44.5 %in group B (p=0.04 and p<0.01 respectively). CRF increased 20 % in group A and 232.1 % in group B (p=0.66, and p<0.01respectively). CH and CRF increase was more important in group B at all time points. CH was significantly higher at week 1, and 3 (p= 0.04, and p < 0.01 respectively) and CRF only at week 3 (p< 0.01) when both groups were compared. We did not find a significant CCT variation in group A (p>0.09). On the other hand, group B showed a significant increase in CCT at all time points (p< 0.01).
The presence of the corneal epithelial layer does not prevent corneal biomechanical changes to develop after UV CCL, but it seems to significantly diminish CH and CRF changes.
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