Implantation and Removal Procedures
Implantation and Removal Procedures
The surgical procedure* for placing Retisert® (fluocinolone acetonide intravitreal implant 0.59 mg, Bausch + Lomb) is relatively straightforward and does not involve a steep learning curve for retinal surgeons, who are accustomed to working in the back of the eye.
The procedure can be performed under general anesthesia or utilizing retrobulbar or peribulbar block. The implant is usually placed in the inferotemporal or inferonasal quadrant, which preserves superior conjunctiva in the event that IOP-lowering surgery is required in the future. Before the procedure, the surgeon or a technician should tie an 8-0 double-armed polypropylene suture to the implant's suture strut. This is supplied with the implant and used to secure it to the scleral wall.
Step one, a conjunctival peritomy, is followed by creation of a 3.5-mm full-thickness sclerotomy at the pars plana, approximately 3.5 mm posterior to the limbus. It is important to make sure the incision is all the way through the choroid so the implant does not become trapped in the subchoroidal space. The blade used to make the incision should be visible through the pupil. Next, a small amount of vitreous is removed, and a single throw is placed over the suture strut. The throw helps to ensure the implant is recessed into the posterior chamber and the strut is not in the wound.
At this point, the implant should be inserted through the center of the wound. Before it is secured in place with the 8-0 suture, the surgeon should verify that the implant has passed through the full scleral thickness. Also, the drug-release orifice should be facing the front of the eye. Once placement of the implant is double-checked, the anchor suture should be tightly tied, with the tails left long. The ends can then be secured with 9-0 polypropylene sutures on either side of the implant.
It is often recommended that two interrupted sutures be placed on each side of the implant. In my experience, one on each side is sufficient for tight closure of the wound. Surgeons use a variety of closure techniques. I prefer to tie a slip knot for each suture. This works somewhat like a noose; as I continue to pull the suture, it continues to tighten down. Also I can use the tension it creates to rotate the ends into the wound so they do not protrude through the conjunctiva and irritate the patient. Once the 9-0 sutures are secure, the procedure is completed with the replacement of the conjunctiva over the incision site.
RISKS ASSOCIATED WITH IMPLANTATION PROCEDURE
As with all surgical procedures, it is extremely important that the wound is adequately closed after Retisert implantation. Late onset endophthalmitis has been observed. Other potential complications include cataract formation, choroidal detachment, hypotony, increased IOP, exacerbation of intraocular inflammation, retinal detachment, vitreous hemorrhage, vitreous loss and wound dehiscence.
REPLACING THE IMPLANT
As Retisert (fluocinolone acetonide intravitreal implant 0.59 mg, Bausch + Lomb) is depleted of fluocinolone, inflammation may recur, and a second implant can be placed in the eye. It is at the discretion of the physician whether to remove the original implant or leave it in place and implant the new one at a different surgical site. I prefer to leave the original implant in place rather than expose the patient to the risks of a removal procedure. None of my patients has required a third implant. If that situation arose, I would remove one of the first two.
When replacing an implant at the original surgical site or in a previously vitrectomized eye, it may be helpful to place an infusion line for the procedure. The positive pressure produced by infusion can help keep blood out of the vitreous if bleeding occurs. Infusion may also help to push the original implant into the incision, making removal easier and preventing it from falling into the vitreous cavity.
As noted in the full prescribing information for Retisert, in vitro studies have shown that with prolonged hydration the strength of the adhesive bond between the implant's suture tab and the silicone cup reservoir, which contains the fluocinolone acetonide tablet, is reduced. This means the potential exists for separation of these components. Therefore, caution should be exercised to avoid placing shear forces on the implant during explantation and implantation. The implant should be handled only by the suture tab.
Figures 1-5. Dr. Wang implants a fluocinolone sustained-release device (Retisert, Bausch + Lomb), beginning with a conjunctival peritomy. The implant is placed into the back of the eye through the center of a 3.5-mm incision at the pars plana and sutured (8-0 polypropylene) to the scleral wall. After the anchor suture is tied, its ends are secured with 9-0 polypropylene sutures on either side of the implant so the wound is tightly closed.
Published studies have shown the results of implanting a second Retisert implant to be similar to outcomes with the original implant. In general, inflammation is again brought under control, use of other medications can be reduced, and visual acuity stabilizes or improves.
Jaffe14 reported results from a prospective, interventional study in which 17 eyes of 14 patients received a second implant. Average follow-up time after the second implant was 17 months. Inflammation recurred in only one of the eyes, 3 years after the second implant. At 12 months after the second procedure, average visual acuity was 20/78 compared with 20/400 at the time of the original implant.
In a retrospective observational case series published by Taban and colleagues,15 10 eyes of 10 patients underwent Retisert reimplantation. Visual acuity stabilized or improved in all 10 eyes after both the first and second implantations. After the first implantation, inflammation had recurred after a median time of 32.5 months. After the second implantation, inflammation recurred in four eyes during the follow-up period, which was a median of 16.8 months. Kaplan-Meier statistical analysis was used to estimate median time to inflammation recurrence after the second implant, which was 25-30 months.
At the time of the first implantation, four of the eyes were phakic. All of them had cataract surgery prior to receiving the second implant. Five of the eyes in the study needed IOP-lowering surgery after the first implantation, and one eye required it after the second implantation. The authors of the paper also reported that one vitreous hemorrhage occurred after the first implantations, and one rhegmatogenous retinal detachment occurred at the site of a second implant.
As previously mentioned, surgeons removing a Retisert implant should be aware of the potential for the medication reservoir to separate from the anchoring strut during the procedure, which was described by Yeh and colleagues.16 In two of the three cases where this occurred, the reservoir fell into the vitreous cavity. To retrieve them, the surgeons performed a pars plana vitrectomy and used intraocular foreign body removal techniques. They used either viscoelastic or perfluorocarbon to elevate the stray reservoirs so they could be safely removed.
As a result of their experiences with this complication, the authors of the paper recommend opening the sclerotomy for the removal procedure to 4 mm and retracting the scleral edges wide enough to reduce shearing forces on the implant as it is being taken out of the eye. They also recommend other surgeons anticipate the possibility of this complication and place an infusion line to prevent wound collapse, improve visualization of the implant and potentially prevent a separated reservoir from descending deep into the vitreous.
*This description of the surgical procedure is included for educational and illustrative purposes only. It is not intended as medical advice or a recommendation by Bausch & Lomb of any particular surgical procedure.
Retinal Physician, Issue: March 2011