[Intraocular silicone oil tamponade. A clinico-pathologic study of 36 enucleated eyes]

Previous histological studies have shown that intraocular silicone oil induces irreversible changes in ocular tissues, especially the retina. The purpose of this study was to analyze, in a larger group of enucleated eyes, changes in intraocular tissue after silicone oil injection, dependent on intraocular pressure, how long the oil was in the eye, and the viscosity of intraocular silicone oil.

We did histological examinations on 36 enucleated globes with intraocular silicone oil after vitreoretinal surgery and compared them with 68 enucleated globes treated with buckle and encircling band using immunohistochemistry (n = 5) and electron microscopy (n = 7). For statistical evaluation we used the chi(2) test and analysis of variance.

After silicone oil injection we observed a more pronounced reduction in corneal endothelial cells (58%), more frequent closed chamber angle (86%), atrophy of the ciliary body (80%) (P < 0.05), proliferative vitreoretinopathy (89%), and glaucomatous atrophy of the optic nerve (56%) (P < 0.01). The retinae showed independent of the use of silicone oil a loss of inner and outer segments of photoreceptors and of ganglion cells and thinning and rareficaton of all other retinal layers. Globes with silicone oil revealed vacuoles both free and incorporated by macrophages in all layers of the retina. Similar vacuoles were seen in the optic nerve, choroid, retinal pigment epithelium, ciliary body, iris, chamber angle and the corneal endothelium. Silicone oil vacuoles were seen in the retina and optic nerve by 1 month after surgery in two eyes with high intraocular pressure (42 mmHg). Six of eight eyes with normal intraocular pressure levels showed retinal vacuoles, 3 of them after 2 months. Vacuoles in the optic nerve were found in eight of nine eyes with intraocular instillation of 1000 mPa silicone oil. There was no clinicohistopathological correlation between the presence of vacuoles in the retina or optic nerve and the duration and viscosity of intraocular silicone oil.

This study suggests that vacuoles in eyes with silicone oil instillation can be found in the retina after 4 weeks. The period of intraocular silicone oil should be limited to 3-6 months.