Another unusual complication of silicone oil is migration of the oil away from the vitreous cavity. In some cases silicone oil has been reported to migrate along the optic nerve, usually in eyes with elevated intraocular pressure and glaucomatous cupping. One patient developed a hemianopsia in the contralateral eye after migration of silicone oil to the optic chiasm.34 In this case, the patient had elevated intraocular pressure with total cupping of the optic nerve in the oil-filled eye. Neurosurgical evacuation of oil from the chiasm led to improvement in the visual field defect. In other cases, neuroimaging has indicated the presence of silicone in the brain.36,80

Budde et al performed histopathologic analysis on 74 eyes enucleated after silicone oil tamponade, finding vacuoles along the optic nerve (suggesting silicone oil migration) in 24% of eyes.15 Interestingly, a study of 20 cadaveric eyes with postmortem infusion of silicone oil at high pressures found no evidence of silicone oil along the optic nerve at 16 weeks.76 The authors speculated that pre-existing nerve damage or active transport mechanisms may be involved in silicone oil migration.

Silicone oil is indispensable in vitreoretinal practice and is generally safe when used appropriately. A Silicone Study report of patients with sustained macular reattachment for 3 years after surgery showed no evidence of further visual decline 6 years after the initial surgery.1 Patients with prolonged or permanent tamponade with silicone oil, however, must be monitored regularly. The clinician must rule out more common causes of vision loss, including corneal toxicity (band or bullous keratopathy), cataract, refractive error, retinal detachment, ERM, cystoid macular edema, and secondary glaucoma in patients experiencing vision loss while having long-term silicone oil tamponade before considering the complications discussed here.