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(Sofia) Xin Tan, Daniel H. hammer, Anant Agrawal, Ilko Ilev; Corneal thinning during UVA-riboflavin cross-linking procedures and the effect of dextran concentration in the riboflavin solution. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4314.
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© ARVO (1962-2015); The Authors (2016-present)
Safe protocols for corneal cross-linking (CXL) require corneal thickness of at least 400 μm for protection of corneal endothelium, lens, and retina. Corneal thinning during the CXL procedures poses severe risks of intraocular damage especially for patients with thin corneas and therefore is a safety concern for the CXL treatment platforms. The riboflavin formulation adds another dimension of complexity for corneal thinning, and exploratory approaches have been undertaken to reduce the standard dextran concentration or replace it with other polymers. In this study with ex-vivo bovine eyes, we monitored corneal thinning and the effect of varying dextran concentrations on corneal thinning during the CXL procedures with deep-scan optical coherence tomography (OCT).
CXL experiments were performed on enucleated bovine eye globes from a local slaughter house using a 365-nm UVA-LED irradiation system based on the standard protocol (30-min riboflavin instillation followed by 30-min UVA light exposure at 3mW/cm2) and also with varying dextran concentrations (20%, 15% and 10%) in the riboflavin solution. Corneal thickness was monitored before and after the application of riboflavin-dextran solution and again after UVA light exposure using a 1070-nm OCT imaging system.
The de-epithelized bovine corneas underwent a dramatic decrease in corneal thickness after the application of riboflavin-dextran solution and further decrease after UVA illumination. For the standard 20% dextran riboflavin solution, the corneal thickness decreased ~20-25% after riboflavin instillation and further decreased ~7-10% after UVA exposure. For 15% dextran riboflavin solution, the decrease in corneal thickness ranged ~15-20% after riboflavin instillation and further ~3-5% after UVA exposure; and for 10% dextran riboflavin solution the corneal thickness decreased ~10-15% and further ~3-5% respectively.
It is important to carefully monitor the changes in corneal thickness during the CXL treatment especially after the application of riboflavin-dextran solution when the decrease is largest. CXL treatment parameters and riboflavin formulation need to be fine-tuned to reduce corneal thinning so as to avoid delivering an endothelial cytotoxic dose especially for patients with thin corneas.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
UVA-LED for Corneal Cross-linking and OCT Imaging to Monitor Changes in Corneal Thickness
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