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Evan Sherr, Pavel Kamaev, Sara Rood-Ojalvo, Marc Friedman, David Muller; Impact of Riboflavin Formulations on Corneal Hydration. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5274.
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Corneal collagen cross-linking (CXL) with riboflavin (RF) strengthens corneas with signs of keratoconus. The procedure involved the application of a riboflavin solution to the cornea for a period of time, followed by exposure to UV-A illumination. A number of formulations have been employed to deliver RF to the cornea, which have either intended or unintended impact on corneal hydration, and associated swelling or shrinkage. The purpose of this study is to evaluate, in-vitro, the relative impact of various riboflavin formulations on corneal hydration.
Iced rabbit eyes, shipped overnight from Pel-Freez Biologicals (Rogers, Arkansas), bathed in saline. Epithelia were removed off thawed eyes, and placed in a humidified, CO2 and Dulbecco’s medium-containing container with a lid and kept for 1 hour at 35 0C. Once stabilized, initial corneal thicknesses measured with an ultrasonic Pachymeter (DGH Technology, Exton, PA). Then solutions of: (A) 0.12% RF, 1.0% Hydroxypropyl methyl cellulose [HPMC], 0.9% Phosphate Buffered Saline [PBS] (VibeX(TM) Rapid, Avedro, Inc.); (B) 0.12% RF, 20% Dextran 500, 0.44% PBS (Vibex(TM)); (C) 0.25% RF, 0.9% PBS (Vibex(TM) Xtra}; and (D) 0.1% RF in distilled water, were applied by drops every 3 minutes and the corneal thicknesses were measured. The same procedure, without epithelium removal, was used for evaluation of solution (E) containing 0.25% RF, 0.85% HPMC, 0.44% PBS, 0.02% Benzalkonium chloride [BAK], 0.1% EDTA (Paracel(TM), Avedro, Inc.). Between measurements, eyes were kept in the same humidified closed container at 35 0C.
Over the course of 21 minute application, solutions produced the following behavior: 20% Dextran (B) and distilled water (D) containing formulations led to approximately 60% and 30% corneal thinning, respectively; HPMC containing solutions (A, E) resulted in less than 10% corneal thinning; hypotonic saline solution resulted in 10% corneal swelling.
Various applications of CXL require management of corneal hydration. The removal or disturbance of corneal epithelium alters the fluid balance of the cornea, typically causing swelling. Composition and formulation of CXL solutions can predictably manage corneal hydration.
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