In vivo formation of heavy oil

A case of silicone oil adhered to the retinal surface via perfluorocarbon liquid

Background

Perfluorocarbon liquid (PFCL) is widely used as an intraoperative heavy tamponade to flatten the retina and is replaced with silicone oil (SO) at the end of the surgery. Due to the long tamponade period, the SO is known to remain attached to the retina at the time of removal, and is commonly termed “sticky oil”. The aim of this present study was to report a case of SO stickily attached to the retina via PFCL without tamponade period.

Case presentation

A 39-year-old male was referred to our hospital due to decreased vision and visual field defect in his right eye. Upon examination, he was diagnosed with rhegmatogenous retinal detachment in that eye. For treatment, he underwent vitrectomy with the use of PFCL and SO. The direct exchange of PFCL with SO resulted in residual subretinal fluid, so we subsequently attempted to remove the SO. However, a SO bubble adhering to the PFCL was visible on the posterior pole. After aspiration of the PFCL beneath the sticky SO, the SO was easily separated and removed from the retina.

Conclusions

Our findings show that SO can become tightly adhered to the retinal surface via PFCL during vitrectomy, and that the sticky SO can be safely removed via aspiration of the PFCL layer underneath the SO.

STICKY SILICONE OIL

OBJECTIVE

To report and analyze the phenomenon of sticky silicone oil on the retina at the time of its removal.

BACKGROUND

Silicone oil has been used for more than 25 years as a long-term retinal tamponade in the surgical management of patients with complex retinal detachments. When a decision to remove silicone oil was made at the end of the tamponade period, the system involved a number of different materials: silicone oil, aqueous solution with or without remnants of perfluorocarbon liquid plus the material of the cannula used to aspirate Silicone oil. This, in effect, may lead to an abnormal adherence of large bubbles of residual silicone oil to the posterior pole of the retina.

PATIENTS AND METHODS

A retrospective, interventional case study was performed. We consecutively reviewed 796 patients of silicone oil removal (5,000 or 5,500 centistokes) after primary pars plana vitrectomy at one vitreoretinal center operated by a single surgeon (HG). Chart review was performed to identify potential patients or procedural factors that could predispose to sticky silicone oil formation at the macular area.

RESULTS

Large silicone oil bubbles were sticky to the macula in eight out of 796 silicone oil removal procedures between January 2014 and August 2015. The use of perfluorooctane was related to the occurrence of the phenomenon (P < 0.001).

CONCLUSION

The sticky silicone oil bubble at the macular region was not related to internal limiting membrane peeling, epiretinal membrane, viscosity, duration, or brand of silicone oil used, but to the use of perfluorooctane.

Entrapped preretinal oil bubble: report of two cases

BACKGROUND

Retained preretinal bubbles were found over the posterior retina after silicone oil removal in patients who had received complicated vitreoretinal surgery.

CASE

We report on two patients who underwent vitreoretinal surgery with silicone oil infusion for giant retinal tears; perfluorocarbon liquid was used during the surgery. Posteriorly located preretinal oil was noted after silicone oil removal in both patients.

OBSERVATIONS

In both cases, oil bubbles formed, which were transparent and located in unusual places for a long period of time. No alteration of refractive status or harmful effect seemed to be associated with these retained oil bubbles.

CONCLUSIONS

This strange phenomenon of fixed preretinal oil bubbles may occur after vitreoretinal surgery. It did not seem to be harmful to the retina during the follow-up periods.

Interactions of perfluorocarbon liquids and silicone oil as characterized by mass spectrometry

BACKGROUND

Perfluorocarbon liquids (PFCL) are used extensively in complex vitreoretinal surgery, sometimes before the placement of silicone oil (SiO). We suspected that PFCL and SiO interact physically when in opposition, potentially making their removal more difficult. The nature of some of these interactions was explored using a mass spectrometric approach in in-vitro and in-vivo samples.

METHODS

We incubated silicone oil (1,000 or 5,000 centistokes viscosity) and PFCL [perfluoro-n-octane (PFO) or perfluorotributylamine] together in vitro for 6 months and performed electron impact ionization mass spectrometry (EIMS) on the PFCL to characterize interactions between the liquid phases. Packaged samples of PFCL served as controls. We also examined in vivo samples of PFO which had been retained in human eyes for several months prior to surgical removal.

RESULTS

Perfluorocarbon liquids packaged for surgical use all contain SiO in trace amounts, possibly as a manifestation of the processes used in their manufacture. Furthermore, all PFCLs incubated with SiO showed much more prominent contamination with SiO molecular fragments. PFCL was found in the SiO phase of eyes in which both liquids were present for extended periods of time. The EIMS analysis of in vivo samples suggested that proteins coat PFCL droplets, forming micelle-like structures.

CONCLUSION

Medical-grade PFCLs contain small amounts of SiO, and PFCLs dissolve small amounts of oil into solution over time. Interactions between retained vitreous substitutes may have clinical relevance.

Determination of the solubility of perfluorocarbon liquids in silicone oil in vitro and in vivo

PURPOSE

To investigate the solubility of perfluorocarbon liquids (PFCL) in silicone oil.

METHODS

Forty-eight samples of silicone oil (1,300 mPas, n = 22; 5,000 mPas, n = 26) were analyzed for dissolved fluorocarbon molecules after surgical removal from patients who had initially undergone vitreoretinal surgery with (n = 41) and as control without (n = 7) the use of perfluorodecalin in headspace gas chromatography. In vitro, the solubility of three different PFCL-perfluorooctane (PFO), perfluorodecalin (PFD), and fluoromethylcyclohexane (FMCH)-in silicone oil of various viscosities was determined. The diffusion phenomena during a direct exchange were studied.

RESULTS

In 39 of 41 silicone oil samples removed from patients who had undergone vitreoretinal surgery with the use of PFD, small amounts of dissolved perfluorocarbons could be detected. The mean value in 5,000-mPas silicone oil was 939.0 x 10-4 m/% and in 1,300-mPas silicone oil was 322.75 x10(-4) m/%. No perfluorocarbon molecules were found in seven control patients. In vitro, the following maximum solubilities in 1,000-mPas silicone oil were measured at room temperature: PFO, 3.2 m/%; PFD, 5.1 m/%; and FMCH, 10.3 m/%. The maximum values measured in 5,000-mPas silicone oil were PFO, 3.3 m/%; PFD, 5.7 m/%; and FMCH, 8.5 m/%; and in 100-mPas silicone oil were PFO, 2.4 m/%, and PFD, 5.1 m/%.

CONCLUSION

Perfluorocarbon liquids dissolve in silicone oil. This may lead to transient formation of "heavy silicone oil," but no stable heavy silicone oil can be created adding PFCL. Intraocularly, retained PFCL vanish in silicone oil and are removed during silicone oil removal.