To the Editor.
—A misconception about chelation has permeated much of the ophthalmological literature. EDTA has been used to chelate Ca++ both in vitro and in vivo. Chelation of Ca++ is of interest in ophthalmology because Ca++-dependent enzymes from bacteria, epithelium, or leukocytes may be important factors in the pathogenesis of corneal ulcers. Topically applied chelating agents may inhibit enzyme activity and prevent corneal injury. Chelation has also been used to remove calcium deposits in band keratopathy.The misconception is that EDTA has two binding sites for Ca++. CaNa2EDTA has been used both in vitro1-3 and in vivo4 for the purpose of chelating Ca". A review article erroneously states that EDTA has two binding sites for Ca++.5CaNa2EDTA does not bind additional Ca+ +. Each molecule of EDTA binds only one Ca++ ion.6The only form of EDTA in the drug formulary
Davis SD, Chandler JW. Misconception About Chelation. Arch Ophthalmol. 1974;92(4):362. doi:10.1001/archopht.1974.01010010372028
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