How long can silicone oil stay in eyes?

Wound closure

Not to be confused with tapenade

Not to be confused with cardiac tamponade

Tamponade ([1]) is the closure or blockage (as of a wound or body cavity) by or as if by a tampon, especially to stop bleeding.[2] Tamponade is a useful method of stopping a hemorrhage. This can be achieved by applying an absorbent dressing directly into a wound, thereby absorbing excess blood and creating a blockage, or by applying direct pressure with a hand or a tourniquet. There can, however, be serious consequences when a tamponade occurs as a result of health problems. For example: cardiac tamponade is a condition where fluid collects in the pericardial sac increasing pressure within the pericardium which in turn prevents the ventricles from expanding fully significantly reducing the efficiency of the heart. It is considered a medical emergency and if left unchecked is fatal.

Bladder tamponade is obstruction of the urinary bladder outlet due to heavy blood clot formation within it.[3] It generally requires surgery.[3] Such heavy bleeding is usually due to bladder cancer.[4]

Pressing bone wax into bleeding bone is considered hemostasis by tamponade, as opposed to methods which physically or biochemically activate the clotting cascade.

Gas tamponade has been used for retinal detachment surgery, helping reduce the rate of fluid flow through retinal tears. Research suggests that patients undergoing surgery with tamponade agents of C3F8 gas and standard silicone oil had the best visual and anatomic outcomes, over other tamponade agents.[5]

References

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In this study, we investigated the effects of long-term silicone oil on the central retina, optic disk, and choroid of the study eyes as compared to that of the sound eye by OCT imaging. The study results point that long-term silicone oil retention in the eye greatly affects the inner retinal layers. The statistically significant thinning in the temporal RNFL of study eyes as compared to that of control eyes further supports this finding. Additionally, the absence of a statistically significant difference in the CTs when compared to the control eyes suggests that the nutrition of the outer layers of the retina and optic disk may not be compromised because of silicone oil. Another remarkable finding in our study was the strong positive correlation between INL thinning and final visual acuity. Recent studies have demonstrated the variability of MT and RNFL-T in healthy individuals; therefore, we assumed that it would be more appropriate to use the other healthy eye of the same individual as controls [6].

Silicone oil is preferred as a long-term endotamponade that enhances the success rate of detachment repair and anatomical recovery with its hydrophobic nature. It has been selected especially for retinal detachments with giant tears and with ≥ group B PVRs [7]. Emulsification of silicone oil is the main reason that promotes the most common complications in the anterior and posterior segments of the eye. The amount of time silicone oil remains in the eye is the most crucial factor in the development of emulsification and so in reducing its complications [8]. The effects of long standing silicone oil on the retina has not been sufficiently investigated yet.

The effects of silicone oil on the retina and the causes of vision loss after removal have been previously investigated in several studies. Although animal studies have reported discordant results, first clinical OCT studies about morphological changes after successful macula-on or macula-off detachment surgeries focused on the alterations of outer retinal layers associated with poor visual outcomes [9,10,11,12,13,14,15]. Former OCT studies highlighted that the central foveal thickness alterations due to silicone oil tamponade was correlated with the final vision acuity level [14, 15]. Christensen and la Cour reported severe visual loss associated with significant retinal (subfoveal) thinning after the use of silicone oil in 33% of patients who underwent macula-on RD. [13] Bolukbasi et al. reported statistically significant thinning in the subfoveal choroidal thickness; and Delolme et al. presented outer retinal layer changes with the successful repair of rhegmatogenous RD. [12, 16] Although alterations of the photoreceptor outer segments and changes in the IS/OS band had been previously accused, later studies suggested that the thinning of inner retinal layers and ganglion cell loss may be the potential reasons of vision loss [17, 18].

Although ganglion cells gradually decrease with age, silicone oil is blamed for the pathological death of retinal ganglion cells [19]. Lee et al. have found that retinal thickness, GCL, outer plexiform layer, and outer nuclear layer thicknesses were significantly thinner in the silicone oil group with a mean duration time of 101 days when compared with gas-filled eyes [18]. Caramoy et al. reported reduced ganglion cell and IPL even in short-term silicone oil–based endotamponade [20]. The potential mechanisms blamed for significant thinning were inflammatory process due to hyper reactivity toward silicone oil/emulsified silicone oil, which resulted in apoptotic cytokine discharge, dysfunction of Muller cells, and retinal toxicity [21,22,23]. All these previous studies have been performed in primary rhegmatogenous RDs or uncomplicated vitreoretinal surgeries. On the contrary, our study focused on complicated surgeries with long-term silicone oil tamponade. However, to date, we have not seen a study that investigated silicone oil–related changes in eyes with such a long period of retention time.

In complicated RD surgeries, anatomical success was defined as retinal reattachment and functional success was defined as the achievement of vision better than 5/200 [24]. Although the retinal reattachment can be achieved at the end of complicated vitreoretinal surgeries, its functional results were unsatisfactory [25, 26]. The reason of this discordance is exactly unknown; however, the severity of underlying diseases and prolonged silicone oil tamponade may be the etiological factors. Although there is no study showing the effects of long-term silicone oil tamponade, Scott et al. showed a significant correlation between an early removal of silicone oil and an improved visual acuity [25]. Our study is the first one that investigates the retinal and choroidal morphological differences in eyes with longstanding silicone oil tamponade. Our study showed that there was no change in the CT as compared to the other eye even in cases where silicone oil remained for a long time. Moreover, we found that silicone oil mainly affected the inner retinal layers, and there was significant thinning of GCL, INL, and RNFL. In our study, the main reason why silicone oil remained in the eye for a longer time is that the patient did not comply with the surgery program and did not come to follow-up visits. However, it will be critical to remove the silicone oil tamponade as early as possible to minimize the thinning effect, especially on the inner retinal layers.

The main question to be asked for this study is whether the retinal changes revealed are due to complicated RD or long-term silicone oil retention. (over 6 months). The main retinal region where pathological changes are observed after RD are the photoreceptor sequence and outer retinal layers [27]. Additionally, the effect of silicone oil on the retina is related to the time it stays in the eye rather than its physical properties. Long-term tamponade with silicone oil for more than 9 months causes an increase in the arteriovenous flow difference and narrowing of the retinal arterioles [28].

Limitations of our study are its retrospective nature, small sample size, and nonrandomized patients. We included mostly macula-off recurrent RDs, some of which needed perfluorodecalin for reattachment and some needed cataract removal at the same session. Different types of silicone were used and the choice of silicone oil was solely determined by the surgeon at the time of surgery. Multiple surgeries, previous solved macular complications like epiretinal membranes, and probable undefined emulsification of silicone oil weakened the standardization.

The effects of silicone oil on the retina remain uncertain, but morphological results in our study have shown direct or indirect silicone oil–induced toxicity, especially in the inner retinal layers. Prospective long-term studies with a large sample size are needed to confirm our observations.