Penetration of mercury from ophthalmic preservatives into the human eye

Single corneas of nine patients about to undergo full-thickness corneal keratoplasty were exposed to thiomersal by application of a hydrophilic gel contact lens preserved with this mercurial agent. These lenses were removed at operation 4 h later, and the lenses, corneal buttons, and samples of aqueous were taken for determination of total mercury by wet digestion and flameless atomic absorption. The contact lenses contained little residual mercury, but mercury was readily detected in the corneal buttons and in the samples of aqueous over the range of 1--60 ng/ml. Five control samples of aqueous obtained without exposure to mercurial preservatives contained less than 1 ng/ml mercury. Although specific effects on ocular function are not described, the use of these preservatives is associated with penetration of mercury into the aqueous in concentration similar to those reported with systemic poisoning by organic mercurials.