Eye Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
Mehrdad Motamed Shariat
Tel: +989377388690
Email: mehrdad_shariati2005@yahoo.com
Received : Jan 12, 2023 Accepted : Feb 20, 2023 Published : Feb 27, 2023 Archived : www.meddiscoveries.org
Polydimethylsiloxane, known as silicone oil, belongs to a group of polymeric organosilicon compounds and is widely used in vitreoretinal surgery. The five physical properties of silicone oil (SO) that make it valuable in vitreoretinal surgeries include transparency, viscosity (1000-5000 centistoke), biocompatibility, high interfacial surface tension in aqueous solution, and positive buoyancy. The primary use of SO is to tamponade the retina in patients with rhegmatogenous retinal detachment (RRD) following pars plana vitrectomy (PPV) and endolaser photocoagulation until the chorioretinal adhesion is established [1].
Considering that SO is a biocompatible and safe compound, its use as a tamponading agent is very common in the field of vitreoretinal surgery. However, some postoperative complications have been reported about using SO. Table 1 summarizes previous study results regarding the complications associated with using SO.
In some patients with a history of PPV with SO injection, unexplained vision loss has occurred. Experts have proposed a variety of mechanisms to justify this finding. Retinal toxicity of SO can be due to the direct toxicity of small emulsified silicone particles on the retinal ganglion cells, modifications in the microcirculation of the macula or optic nerve head, and the neuro-destructive effects of growth factors that are sandwiched between the retinal surface and SO. Some studies have shown a significant positive correlation between the incidence of visual impairment and the duration in which SO has remained inside the vitreous. Furthermore, intraocular pressure rise is another significant factor affecting patients' visual status after using SO as a tamponade.
The presence of low-molecular-weight components (LMWCs) in SO is one of the factors contributing to retinal toxicity. LMWCs are composed of repeating dimethyl-siloxane units with a molecular weight of less than 2400 Dalton and are the most abundant component in all chemical impurities. In a study in 2021, Ying Chen et al. investigated the cytotoxic effects of LMWCs on retinal cells. They showed that most LMWCs have cytotoxic properties in liquid and emulsified forms and induce apoptosis in retinal cells [8].
| Authors | Year | Complications of SO |
|---|---|---|
| Yang et al [2] | 2007 | SO is cytotoxic for corneal endothelial cells and has to be removed as soon as possible |
| Pichi et al [3] | 2020 | Particles of oil that migrate into the retina or come into direct contact with it both have the potential to cause direct damage to ganglion cells. Due to silicon oil's transparency, indirect harm may result from phototoxicity or inflammation brought on by cytokines wedged between the oil and the retina. |
| Federman et al [4] | 1988 | Cataracts developed in all phakic eyes during a follow-up period of 5 years. Band keratopathy occurs during 6 months when touched with SO. Pupillary block glaucoma occurred in 3% of patients. Fibrous epiretinal proliferation occurred in 15% of patients. Subconjunctival deposit of SO was observed in 3% of patients. |
| Miller et al [5] | 2014 | Keratopathy and glaucoma are common complications following SO emulsification. |
| Newsom et al [6] | 2004 | Unexplained vision loss after SO removal in 7 patients with good visual prognosis was reported. |
| Roca et al [7] | 2017 | After SO removal, 5.9% of eyes showed unexplained vision loss. Higher IOP and a longer SO tamponade time were factors linked to this occurrence. |
Although employing SO for long-term tamponade in vitreoretinal operations is a safe and low-complication alternative, its prolonged stay in the eye can have adverse effects like vision loss. More extensive research is required to comprehend the side effects and etiopathogenesis of vision impairment related to SO treatment.
