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Arch Ophthalmol. 2002;120:831-832.

Silicone oil use as an adjunct to complicated vitreoretinal surgery is becoming more frequent. Refractory glaucoma in these patients is common. Isolated reports have mentioned the possibility of silicone oil migrating and/or obstructing the tube in the anterior chamber of Molteno implants (IOP, Costa Mesa, Calif).^1-2 This report describes a case of intraocular silicone oil egressing through an Ahmed implant (New World Medical, Rancho Cucamonga, Calif), impairing the functioning of the tube and requiring replacement of the implant plus oil removal. We present photographic documentation of the oil progressing through the tube and histopathologic analysis of the orbital tissue surrounding the extruded silicone oil.

Report of a Case
A 69-year-old white man lost his left eye to trauma at age 12 years. In September 2000, blunt trauma resulted in a lacerated eyebrow, scleral rupture, uveal prolapse, extrusion of his crystalline lens, retinal detachment, and suprachoroidal hemorrhage in his right eye. A limited anterior chamber washout was performed at the time of the primary repair. Ten days later, he underwent pars plana vitrectomy, silicone oil injection, and a scleral buckle. A pars plana vitrectomy revision with endolaser, membrane stripping, and silicone oil reinjection were performed 1 month later for a recurrent retinal detachment.

In January 2001, glaucoma surgery was needed to control elevated intraocular pressure (IOP). The eye was aphakic and had total traumatic aniridia. An Ahmed valve was implanted inferonasally in an attempt to avoid the silicone oil bubble (Figure 1 and Figure 2). The patient's IOP responded well initially but rose subsequently to 30 mm Hg. A bubble of silicone oil was wrapping the tip of the tube (Figure 3). Silicone oil could be seen migrating through the Ahmed tube (Figure 4 and Figure 5) and the bleb over the implant progressively enlarged and appeared encapsulated during the next few months. A glistening material was noted in cystic spaces overlying the Ahmed implant under the conjunctiva. An inferior ectropion that progressed gradually was also noted. The volume of the silicone bubble in the vitreous cavity decreased from an estimated 85% fill to an estimated 50% fill. Ectropion repair was necessary in June 2001.

View larger version (37K): [in this window] [in a new window] Figure 1. Slitlamp photograph showing the Ahmed tube inferonasally short after implantation. Notice total traumatic aniridia and superotemporal paralimbal scleral wound with interrupted sutures.

View larger version (30K): [in this window] [in a new window] Figure 2. Retroillumination photograph showing a patent Ahmed tube.

View larger version (27K): [in this window] [in a new window] Figure 3. Slitlamp photograph showing "candle wax" appearance of the silicone oil wrapped around the tip of the Ahmed tube.

View larger version (27K): [in this window] [in a new window] Figure 4. Retroillumination photograph showing a level of silicone oil (arrow) inside the Ahmed tube.

View larger version (29K): [in this window] [in a new window] Figure 5. Retroillumination photograph taken on a different day shows a different level of silicone oil (arrow) inside the Ahmed tube.

Owing to persistently elevated IOP measurements, transcorneal removal of the silicone oil combined with replacement of the Ahmed implant was performed. Multiple silicone oil–filled conjunctival cysts were found surrounding the Ahmed plate. A tissue sample was taken inferotemporally from a thick capsule surrounding the Ahmed implant. Histopathologic analysis of the tissue surrounding the plate demonstrated fibroconnective tissue with numerous small vacuoles. Surrounding this tissue were numerous foreign-body giant cells and histiocytes (Figure 6).

View larger version (60K): [in this window] [in a new window] Figure 6. Histopathologic examination of orbital tissue excised during removal of valve shows empty vacuoles consistent with silicone oil and larger deposit of oil surrounded by epithelioid histiocytes and foreign body giant cells (hematoxylin-eosin, original magnification x200).

Comment
To our knowledge, this is one of the first documented cases of silicone oil exiting the eye through an Ahmed implant. Review of the literature yielded 2 previous reports, both involving Molteno implants in aphakic patients^1-2 and 1 recent report involving an Ahmed implant.³ Minckler⁴ describes adhesion of the silicone oil to the anterior chamber portion of the drainage tube, resembling candle wax, without lumen obstruction. He recommends placing the tube in an inferior location to minimize the chance of oil-tube obstruction. In our case, the inferior location of the tube did not prevent the migration of the silicone oil through the Ahmed implant. The inflammatory reaction observed in the periocular tissues, apparently caused by the silicone oil, has been documented before.^1-2 This contrasts with no observed clinical reaction in intraocular tissues, although histopathologically foreign-body granulomas have been documented in intraocular tissues.

The silicone oil did impair the drainage of aqueous through the implant as evidenced by the elevated IOPs. Encapsulation of the bleb might also have contributed to the obstruction of the implant. The photographs (Figure 3 and Figure 4), showing oil at different levels of the tube, demonstrate the progression of the silicone oil through the tube of the Ahmed implant. We believe that aphakia with total aniridia resulted in an anatomic situation (a truly unicameral eye) that favored the anterior migration of the silicone oil when the patient inadvertently assumed a supine position. This was probably favored by the well-known physical attraction of the silicone tube toward the silicone oil. Once an oil bubble made it to the entrance of the tube, the combined effect of capillary action with elevated IOP may have facilitated the migration of the oil to the subconjunctival space. The patient's IOP has been under control since replacement of the Ahmed implant and removal of the silicone oil. His last corrected visual acuity was 20/50 OD.

It seems that a "unicameral" eye with silicone oil, particularly with significant iris defects, is a poor candidate for successful IOP control with a seton in a 1-stage procedure. In our case, the inferior location of the implant did not prevent silicone oil movement out of the eye with secondary impairment of IOP control. Silicone oil removal needs to be considered prior to implantation of a seton in such cases. If silicone oil removal is not an option, diode laser cyclophotocoagulation is another alternative for IOP control.

AUTHOR INFORMATION

Jose Morales, MD; Michel Shami, MD; Geert Craenen, MD; Thom F. Wentlandt, CRA
Lubbock, Tex

Corresponding author: Jose Morales, MD, Texas Tech University Health Sciences Center, Department of Ophthalmology and Visual Sciences, 3601 Fourth St, STOP 7217, Lubbock, TX 79430-7217 (e-mail: jose.morales{at}ttuhsc.edu).

REFERENCES
1. Hyung SM, Min JP. Subconjunctival silicone oil drainage through the Molteno implant. Korean J Ophthalmol. 1998;12:73-75. PUBMED 2. Senn P, Buchi ER, Daicher B, Schipper I. Bubbles in the bleb: troubles in the bleb? molteno implant and intraocular tamponade with silicone oil in an aphakic patient. Ophthalmic Surg. 1994;25:379-382. PUBMED 3. Nazemi PP, Chong LP, Varma R, Burnstine MA. Migration of intraocular silicone oil into the subconjunctival space and orbit through an Ahmed glaucoma valve. Am J Ophthalmol. 2001;132:929-931. PUBMED 4. Minckler D. Silicone oil glaucoma: cases in controversy. J Glaucoma. 2001;10:51-54. PUBMED

SECTION EDITOR: W. RICHARD GREEN, MD