Influence of topical and oral zinc upon corneal wound healing.

Experimental evidence indicates that the healing rate of avascular penetrating corneal wounds is delayed when compared with vascularized penetrating corneal wounds or with wounds of other vascularized tissues (Gasset and Dohlman, I968; Howes, Sooy, and Harvey, 1929). This is exemplified clinically by a substantial number of postoperative wound healing complications which may occur after penetrating keratoplasty. The complications resulting from the prolonged period necessary for healing of avascular corneal wounds after penetrating keratoplasty are dehiscence of the wound margins, overriding of host-graft wound edges, anterior iris synechiae, iris prolapse, oedema of the donor corneal button, and even total extrusion of the graft. Each of these complications or any combination of them may be sufficient to compromise the viability of the donor endothelium and lead to graft rejection. Although it is well known that topically administered corticosteroids have a deleterious effect on the healing ofavascular corneal wounds, the majority ofpostoperative keratoplasty patients receive topical corticosteroids to prevent or ameliorate the postoperative ocular inflammatory response of the anterior segment. However, because of this hazard, topical corticosteroids are given either in sub-optimal doses necessary for achieving suppression of the inflammatory response, or the drug is withheld during the immediate post-transplant period. Therefore, an agent which would accelerate the healing of avascular corneal wounds or nullify the adverse effects of topical corticosteroids on wound healing would be clinically valuable. In the past many agents have been studied to determine if they are capable of enhancing corneal wound healing, with limited success (Rigg and Rigg, I959; Thomas, I955). Recently, systemically administered zinc has been shown to promote wound healing in both animals and man (Pories and Strain, I966; Pories, Henzel, Rob, and Strain, i967a, b; Strain, Pories, and Hinshaw, I960; Savlov, Strain, and Heugin, I962). The effect of topical antiseptics, including zinc sulphate, upon regeneration of corneal epithelium has been reported (Bellows, I946); however, the effect of zinc on penetrating corneal wounds has not been studied. The present study was therefore conducted to evaluate the effect of topically and systemically administered zinc preparations upon the tensile strength of avascular corneal wounds. All experiments were done in a blind fashion unless otherwise noted. Under the experimental conditions employed, statistical analysis of the data shows that the healing of avascular corneal wounds is neither promoted nor retarded by zinc.