Silicone oil complications mostly manageable
Complications of silicone oil occur when it is inadvertently placed in anatomic areas other than the vitreous cavity, migrates, or emulsifies. Methods for avoiding these issues and their management are discussed in this article.
Reviewed by Derek Kunimoto, MD, JD
Paradise Valley, AZ-Use of silicone oil for retinal tamponade can result in a range of complications. Fortunately, most of these events can be avoided with careful attention to surgical technique or successfully treated if they occur, while those without any known preventive strategies are very rare, said Derek Kunimoto, MD, JD.
Anterior segment complications
Silicone oil in the subconjunctival space presents a cosmetic issue and can also lead to granuloma formation, said Dr. Kunimoto, in reviewing the complications associated with silicone oil based on their anatomic location.
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Avoiding silicone oil in the subconjunctival space requires good scleral closure with the use of small-gauge vitrectomy, said Dr. Kunimoto, managing partner, Retinal Consultants of Arizona, and Director, Scottsdale Eye Surgery Center, Scottsdale, AZ.
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“Silicone oil in the subconjunctival space is becoming more common because of the use of small gauge vitrectomy, but it can be avoided with a good mattress suture and good apposition,” Dr. Kunimoto said.
The options for managing silicone oil in the subconjunctival space include observation if the cosmetic appearance is acceptable to the patient and watching for granuloma formation or surgical intervention by performing a simple conjunctival cutdown.
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“As long as the cutdown is in the correct plane, the silicone oil will come out nicely,” Dr. Kunimoto said.
Anterior chamber, posterior segment
Silicone oil can also be present in the anterior chamber, and that situation can lead to secondary open angle glaucoma, inaccurate IOP measurements, and in severe cases, to corneal decompensation. Keeping the zonules intact during vitrectomy will prevent silicone oil from getting into the anterior chamber. In the setting of an aphakic eye, placement of an anterior chamber IOL or anterior chamber maintaining sutures is advised to provide a physical barrier against anterior migration.
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Treatment of silicone oil in the anterior chamber is done by creating a paracentesis through which the oil can drain passively.
“As long as there is posterior infusion, the oil will follow itself out of the small opening in the cornea,” Dr. Kunimoto said.
Posterior segment complications
Although silicone oil is supposed to be present in the vitreous cavity, its presence does decrease aqueous volume that can pose a problem in patients who are receiving ongoing intravitreal injections. Surgeons can either remove the silicone oil or according to anecdotal reports, they can compensate for the change by adjusting the dosage of the intravitreal injection.
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Silicone oil placed into the vitreous can also migrate into the sub-hyaloid space. This complication, which occurs more commonly in pediatric cases than in adult eyes, will prevent complete oil fill and leave vitreoretinal tractional forces in place that can predispose to recurrent retinal detachment.
“Ensuring creation of a complete posterior vitreous detachment during surgery will avoid silicone oil getting into the subhyaloid space,” Dr. Kunimoto said.
Another posterior segment complication is silicone oil emulsification in a thin layer over the retina. Treatment of that situation requires silicone oil exchange or removal.
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“Silicone oil droplets can also become embedded within the layers of the retina, and there is no known way to avoid these intraretinal deposits,” Dr. Kunimoto said.
Silicone oil can also penetrate or be inadvertently placed into the subretinal space where it will interfere with retinal detachment repair. In addition, silicone oil in the subretinal space raises potential concern about retinal pigment epithelium (RPE) or retina toxicity. Chronic presence of silicone oil in the subretinal space can also lead to retinal atrophy and large retinal cysts, and silicone oil can emulsify in the subretinal space.
“To avoid getting silicone oil in the subretinal space, surgeons should visually confirm that the cannula tip is not in the subretinal space,” Dr. Kunimoto said.
Retinal tears
In addition, they should be cautious about using silicone oil in eyes with large retinal tears or retinectomy greater than 3 clock hours as well as in those with retinal detachments associated with optic nerve pits or macular holes.
Silicone oil can also be present in the subRPE or choroidal space that will cause a choroidal detachment, preventing retinal detachment repair. Potentially, silicone oil in the subRPE or choroidal space might also be toxic to the RPE or compromise choroidal vasculature.
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Proper cannula selection and positioning is the solution for avoiding these complications.
“Do not use a short cannula and make sure the cannula tip is not in the choroidal space,” Dr. Kunimoto said.
The approach to management of silicone oil in the subRPE or choroidal space is similar to the treatment of choroidal hemorrhage or effusion. Surgeons should create a cut down in the sclera with vitreous cavity infusion and then slightly gape open the sclerotomy to allow passive drainage of the oil. Increasing the infusion pressure will facilitate the passive egress of oil. The choroidal detachment will then flatten, enabling repair of the retinal detachment.
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Silicone oil can also emulsify in the vitreous cavity. The risk is lower with use of higher centistoke silicone oil (5000 versus 1000) and management requires vitrectomy or silicone oil exchange.
Migration of silicone oil into the optic nerve, optic chiasm, and cerebral ventricles as well as unexplained central vision loss with a decrease of visual acuity to the 20/200 level are other complications that can occur with silicone oil tamponade that have no known avoidance strategy.
Surgeons should be aware, however, that the risk for silicone oil migration into the central nervous system is increased when optic nerve pits are present.
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Derek Kunimoto, MD JD
This article was adapted from Dr. Kunimoto’s presentation during Retina Subspecialty Day at the 2015 meeting of the American Academy of Ophthalmology. Dr. Kunimoto is a consultant to Allergan, Bausch+ Lomb, DORC, Genentech, and Synergetics.
