Silicone-oil removal using a 20-gauge infusion cannula

SILICONE-oil tamponade is widely used for the treatment of retinal detachment and macular holes. Because prolonged intraocular silicone-oil retention may cause sight-threatening complications such as keratopathy, glaucoma, hypotony, and perisilicone-oil fibrosis, silicone oil should be removed once its tamponade effect is no longer necessary. 1-4 Active drainage techniques utilize a vitrectomy machine to suction silicone oil from the vitreous cavity while passive drainage uses a stream of water to float silicone oil out through an oversized limbal, pars plana, or corneal incision. 5-8 While passive drainage avoids high suction pressures that may lead to retinal traction or redetachment, the prolonged use of surgical instrumentation to retract the drainage incision may traumatize the wound edges and lead to wound leak, hypotony, pain, scleral melt, or infection. We conducted this study to assess the safety and efficacy of a passive silicone-oil removal through a self-retaining cannula inserted into the pars plana.

METHODOLOGY
Ten phakic or pseudophakic eyes underwent removal of low-viscosity silicone oil (Oxane 1300 centistokes, Bausch and Lomb, Rochester, New York). The indications for silicone-oil tamponade and phakic status are shown in Table 1. The mean injected silicone-oil volume was 5.2 ± 1.0 ml (range, 4 to 7).

Surgical Technique
Local anesthesia with intravenous sedation was used. After making conjunctival incisions, a 20-gauge, 4-mm infusion cannula, connected to a 500-ml bottle of balanced saline, was inserted through an inferotemporal, pars plana, stab incision and anchored using vicryl 7-0 sutures. An MVR blade was then used to create a superotemporal pars plana sclerotomy through which a standard 20-gauge 4- mm infusion cannula, which had been previously disconnected from its tubing, was inserted. The infusion-bottle height was then raised to 3 feet and the infusion line opened. Silicone oil was allowed to drain out through the self-retaining cannula until a gush of fluid was visualized from its tip (Figure 1).

The infusion cannula was then removed and the superotemporal incision enlarged to 2 mm using a 15-degree blade. The incision was held open with 0.12 toothed forceps for 2 minutes to drain the remaining silicone oil. The incision was then plugged. Indirect ophthalmoscopy was done to confirm no remaining silicone oil. The incisions were closed with vicryl 7-0. The silicone-oil removal time was measured using a stopwatch set from the moment the drainage cannula was inserted and a gush of fluid was observed. During each postoperative examination, the following data were recorded: presence of floaters, best-corrected visual acuity (BCVA), intraocular pressure (IOP), and results of dilated-fundus examination. Descriptive statistics are reported. Informed consent was obtained from all patients. The study protocol was approved by the Asian Eye Institute ethics committee.

RESULTS
Nine of the 10 eyes (90%) experienced improvement in BCVA from preoperative levels. The mean silicone-oil removal time was 22.0 ± 4.8 minutes (range, 16 to 30); the mean total surgical duration was 29.6 ± 4.9 minutes (range, 24 to 35). The mean silicone-oil flow rate was 0.24 ml/minute (Table 1). Four patients (40%) reported postoperative floaters. There were no cases of keratopathy, wound leak, hypotony, retinal detachment, uveitis, or suture-related complications. The mean follow-up period after silicone-oil removal was 12.0 ± 5.7 months (range, 6 to 23).

DISCUSSION
Our technique of silicone-oil removal differs from the practice of creating an oversized pars plana incision held open with forceps until complete silicone-oil removal. Instead, a readily available, self-retaining extrusion cannula, inserted through a regular-sized incision, served as the conduit for silicone-oil egress. This method is less traumatic for the patient and less stressful for the surgeon. The advantages of this cannula-assisted technique include: (1) less work for surgeons because the surgeon is freed from holding the wound edges open during most of the surgery; (2) less risk for wound maceration, potentially improving wound closure and preventing wound leaks, hypotony, and infection; (3) less surgical trauma as only 2 sclerotomies are needed; (4) less risk for retinal phototoxicity because the surgical microscope light can be turned off during this automated process; (5) less risk for corneal endothelial damage because removal through the pars plana route avoids anterior-chamber turbulence. 9 Compared to active drainage techniques, passive drainage techniques lessen the risk of retinal traction resulting from high-suction pressures. Addition of a third