Etiology of unexplained vision loss after silicone oil removal still unclear

Wu L. Un-explained visual loss following silicone oil removal. Presented at: American Society of Retina Specialists annual meeting; July 28-Aug. 1, 2023; Seattle.

Wu L. Un-explained visual loss following silicone oil removal. Presented at: American Society of Retina Specialists annual meeting; July 28-Aug. 1, 2023; Seattle.

SEATTLE — Cases of unexplained vision loss following silicone oil tamponade removal have been reported over the years. Potential causes have been investigated but remain unclear.

In a presentation at the American Society of Retina Specialists annual meeting, Lihteh Wu, MD, reviewed studies that attempted to find an explanation, extrapolating some of the potential risk factors.

Some authors in the recent past hypothesized that neuronal apoptosis following silicone oil removal may be triggered by sudden changes in potassium concentration. A later study by Scheerlinck and colleagues found that potassium levels are not elevated in retro-oil fluid following silicone oil removal, and this hypothesis was therefore discarded. Phototoxicity due to increased transmission of high-energy blue light in eyes filled with silicone oil was also disproved as a potential cause.

Some light on this phenomenon was shed by OCT and OCT angiography (OCTA) studies.

“In eyes with long-term silicone oil-related visual loss, SD-OCT revealed microcystic macular changes in the inner nuclear layer with loss of retinal nerve fiber layer. These changes are similar to those found in multiple sclerosis-associated optic neuritis and Leber hereditary optic neuropathy,” Wu said.

Using adaptive optics, Mrejen and colleagues noticed that silicone oil particles remain in the eye and impregnate the retinal tissue after silicone oil removal.

A spectral-domain OCT study of seven eyes with unexplained vision loss found “superficial retinal microvasculature damage and ganglion cell apoptosis,” and a larger study found that most eyes with unexplained vision loss had ganglion cell layer thinning.

“Gradual visual recovery may occur but is often incomplete,” Wu said.

An OCTA study found that the foveal avascular zone (FAZ) in the deep capillary plexus was larger and the vascular density lower than in the fellow eye.

“Duration of silicone oil tamponade was significantly correlated with the enlargement of the FAZ, and reduction of vessel density in the deep capillary plexus was lower. So, eyes with silicone oil tamponade may develop vascular insufficiency,” Wu said.

Based on this evidence, he was able to conclude that “IOP and the length of time that the silicone oil remains in the eye may play an important role,” that “eyes with silicone oil tamponade may develop vascular insufficiency,” and that “some eyes may regain some vision.”