Enhancement in corneal permeability of riboflavin using calcium sequestering compounds.

Ethylenediaminetetraacetic acid, ethylenediamine-N,N'-disuccinic acid and ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid are polyaminocarboxylic acids that are able to sequester metal ions. Calcium is implicated in maintenance of intercellular matrix, zonula occludens (tight junctions) and zonula adherens of epithelium and endothelium cells. Corneal epithelium is impervious to many aqueous formulations due to it being lipophilic, whereby transcellular drug transit is resisted, whilst tight junctions restrict access via the paracellular route. Research has shown that integrity of tight junctions breaks down through loss of Ca(2+) for endothelial and epithelial cells. This study investigates different Ca(2+) sequestering compounds and their effect on corneal permeability of riboflavin at physiological pH. Riboflavin is a topically administered ocular drug applied during UV-induced corneal cross-linking for the treatment of keratoconus.