Histopathologic findings of perforated corneas due to ferric ion infiltration

Objective: To report the histopathologic findings of 3 corneal buttons incised from 2 patients during penetrating keratoplasty (PKP) because of corneal perforation due to corneal siderosis. Methods: Three eyes of 2 patients had accidental trauma to the corneas caused by iron fragments; the injuries were initially treated conservatively with antibiotics and therapeutic soft contact lenses. However, the corneal stroma melted and perforated, necessitating corneal transplantation. The corneal buttons removed during PKP were examined histopathologically, and the findings were compared with the slit-lamp biomicroscopic and anterior segment optical coherence tomographic (AS-OCT) findings. Results: Slit-lamp examinations showed that the corneal epithelium was hyperplasic around the area of perforation in 2 eyes 1 month after the injury. Wide areas of the stroma had melted, and the corneas were perforated. The corneal epithelium was atrophic in the perforated corneas 4 months after injury. Histopathologically, the corneal stroma and Descemet's membrane were stained by Prussian blue, suggesting that the ferric ions had penetrated deeper than expected by the slit-lamp examinations. The areas of Prussian blue staining corresponded well with the areas altered in the AS-OCT images. Conclusions: Ferric ions penetrate much deeper into the cornea than estimated by slit-lamp biomicroscopy. The ferric ions can induce stromal melting that can lead to corneal perforation. We conclude that (i) the ferric ion-infiltrated areas can be estimated in the AS-OCT images and (ii) extensive corneal abrasion should be performed to prevent corneal melting and perforation.