In Vivo Effects of Thimerosal on the Rabbit Corneal Endothelium

To assess ultrastructural alterations to the corneal endothelium, eye drops containing (1) vehicle alone or (2) vehicle plus 0.004% thimerosal with or without 0.1% disodium ethylenediaminetetraacetate (Na 2 EDTA) were administered hourly over a 2‐day period to rabbit corneas in vivo . Twenty of the corneas received a 5‐mm keratectomy that removed epithelium and superficial stroma and 10 corneas were left intact. The vehicle alone had no effect on the endothelium of normal corneas. Thimerosal drops with or without Na 2 EDTA caused some clarification of the cytoplasm and dilatation of the endoplasmic reticulum of endothelial cells. The mitochondria had dilated cristae and membrane condensations. After keratectomy and vehicle only drops, the central endothelium showed a marked increase in microvilli and mitochondria) changes. Addition of either thimerosal or thimerosal plus Na 2 EDTA resulted in a slight decrease in membrane activity but an increase in intracellular edema and dilatation and damage to organelles. The peripheral areas were less affected than the center. Although the endothelium was stressed, most changes were considered reversible.