Tolerance and biocompatibility of micronized black pigment for keratopigmentation simulated pupil reconstruction

To study the tolerance and biocompatibility of new mineral micronized pigments for corneal cosmetic pigmentation in an experimental animal model.

Central corneal intralamellar tattoos were performed with a black iron oxide mineral micronized pigment using an irrigating solution as a control. Animals were examined regularly under a slit lamp to detect any signs of inflammation, pigment diffusion, or color changes and neovascularization. The animals were divided into 2 groups, A and B. These groups were followed up at 1 and 3 months, respectively. At the end of this period, confocal microscopy examination was performed before the animals were killed, and their eyes were processed for histopathological examination to determine the level of pigment diffusion and inflammation and the presence of neovascularization.

Clinical findings included 2 cases of minimal inflammation that resolved within 2 weeks and a severe case of inflammation detected 20 days after the surgery. Confocal microscopy at the end of the follow-up revealed normal corneal structures in all the eyes examined, with a layer of highly reflective material in the mid stroma because of the presence of mineral pigment particles. Histopathological examination corroborated clinical results regarding inflammation. No pigment diffusion or changes in color occurred throughout the study, and there were no cases of corneal neovascularization.

Central keratopigmentation presented good cosmetic appearance without adverse effects. These results suggest the adequacy of mineral micronized pigments for successful keratopigmentation. The hen animal model is a suitable model for assaying the biocompatibility and tolerance of micronized pigments in central keratopigmentation.