Silicone oil in the subarachnoidal space—A possible route to the brain?

Is silicone oil optic neuropathy caused by high intraocular pressure alone? A semi-biological model

“…While some authors consider an elevated intraocular pressure to be the main factor for the shift of silicone oil from the vitreous cavity into the optic nerve, others postulate an active transport mechanism 8. A study based on histological examinations found no correlation between the number of vacuoles in the optic nerves and the intraocular pressure measured prior to enucleation 10.…”

“…Histological studies have revealed penetration of silicone oil into the cornea, the ciliary body, the retina, and the optic nerve, and magnetic resonance imaging has even revealed migration of silicone oil into the ventricles of the brain 2 – 7. Elevated intraocular pressure is thought to be the driving force in the pathophysiology of silicone oil optic neuropathy, although some authors have proposed that silicone oil can be actively transported in macrophages 8. The mechanism by which silicone oil migrates into the optic nerve is still incompletely understood.…”

Vitrectomy: when things go wrong

“…This may occur through leaking sclerotomies or through shunt tubes placed for glaucoma [178,179]. Migration of silicone oil into the anterior chamber can be seen in 6% of nonphakic eyes ( Cases have been reported in which silicone oil in the eye migrated into the cerebral ventricles and the subarachnoid space [180][181][182], and light microscopy has identified silicone oil bubbles in the optic nerve and the subarachnoidal space of an enucleated eye that had undergone silicone oil injection [183].…”

Letter of response: Subarachnoid migration of intraocular silicone oil

“…The migration of silicone into the subarachnoid space could be explained by a continuum between the subarachnoid space surrounding the optic nerve and the subhyaloid space [4,5]. This continuum might be involved in other pathologies such as Terson syndrome or papilledema in benign intracranial hypertension.…”

“…Predisposing factors could be added to explain the silicone migration: increased intraocular pressure (higher than 40 mmHg) allowed a communication of silicone oil with the subarachnoid space [5,6]; deep cupping of the optic disk allowed the silicone oil to enter the subarachnoid space by breaking through the cerebral pia [2]; the role of congenital anatomical deformities, which would lead to an abnormal passage between the subhyaloid and subarachnoid space [3].…”