The Efficacy and Safety of Episcleral Pigmentation Removal From Pig Eyes

Abstract

To evaluate the efficacy and safety of removing episcleral pigmentation from pig eyes using a 532-nm Q-switched Nd:YAG laser. Forty-four porcine eyes with episcleral pigmentation were enucleated approximately 3 hours after death. After conjunctival dissection, 0.5×1.0 cm-sized segments of pigmented episcleral surface underwent laser treatment. To determine the minimal energy fluence required for effective episcleral pigmentation removal, the laser output was set to 2, 3.2, 4, 5, and 6 J/cm for 20 eyes. To investigate thermal effects, the surface temperatures of the episclera were measured in the remaining 24 eyes before and after laser treatment in which the minimal energy fluence required to effectively remove episcleral pigmentation was used. Episcleral pigmentation began to fade immediately with a laser setting of 2 J/cm and was satisfactorily removed immediately with a laser setting of 4 J/cm. The increase in surface temperature was 0.90±0.37°C from baseline with a laser setting of 4 J/cm (P>0.05). Light-microscopic analysis showed that levels of melanin granules decreased by laser treatment in all tested episcleral tissues. The retinal pigment epithelium and the choroid were not affected by treatment. However, the collagen fiber structure was damaged after laser treatment with settings of more than 5 J/cm, as showed by the loss of straight profiles, although the damage was confined to the outer one third of the scleral stroma. 532-nm Q-switched Nd:YAG laser treatment is effective and safe for the removal of episcleral pigmentation in pig eyes. Our findings indicate that the laser system may be effective for the removal of episcleral pigmentation in cases of oculodermal melanocytosis, and further investigation is necessary to evaluate long-term safety of laser treatment.