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Postoperative Infectious Tube Erosion
Outside exposure of glaucoma drainage devices can create complications.
BY REGINE PAPPAS, M.D.

Often, we can be challenged with a patient presenting with various and painful symptoms. This can be especially true in patients with a chronic condition such as pseudoexfoliation glaucoma, where patients suffer from ongoing complications.

Even prior treatments might be susceptible to possible complications such as infections if drainage devices become exposed through the conjunctiva. The following is an examination of such a case and the subsequent treatments in attempts to resolve the complications and the underlying issue:

Case Study

In 1998, A 78-year-old white female presented with advanced pseudoexfoliation glaucoma in both eyes. She was noted to have advanced visual field loss splitting fixation superiorly in both eyes.

She was medically managed initially, but was inadequately controlled on maximal medical therapy. She underwent a trabeculectomy with mitomycin C in her left eye in 1999. The following year, she required cataract extraction in the left eye with a BCVA of 20/40 postoperatively.

Over the course of the next year, she developed pseudophakic bullous keratopathy and underwent a corneal transplant in November of 2001 in the same eye. She also had a recurrent history of blepharitis in both eyes and sinusitis. She developed canuliculitis and lacrimal duct obstruction involving her right naso-lacrimal system, which was treated with topical antibiotic and later managed with probing and irrigation of the right naso-lacrimal system in 2002. She had a successful combined cataract and glaucoma filtering procedure in January of 2003 in her right eye with resultant visual improvement to 20/25.

In April of 2003, she presented to the cornea specialist with an IOP of 39 mm Hg in the left eye. She had not been seen at our office due to the fact that her mobility had been restricted because of a foot infection that would not heal and she had been placed in an assisted-living facility. She was diagnosed as having methacillin-resistant Staphylococcus aureus (MRSA) and had ongoing treatment for the infection.

She underwent Baerveldt valve (Advanced Medical Optics, Santa Ana, Calif.) placement with a supramid stent in her left eye in May of 2003. One day later, she complained of a slightly sore eye with the conjunctiva appearing only slightly red and exhibiting lid edema. However, 5 days later, she was returned to the office with pain involving her left eye. She had 2+ chemosis and lid edema. She was started on every 2-hour topical gatifloxacin 0.3% (Zymar, Allergan) and topical prednisolone acetate 1% (Predforte, Allergan).

That evening, she presented to the emergency room in extreme pain and was placed on 1 g cefazolin for injection (Ancef, GlaxoSmithKline) in the ER and sent home with a course of oral antibiotics.

The ER doctor consulted me by phone and a culture swab of her left eye was taken. She also had an elevated white count with a left shift. The culture results later come back as MRSA.

In the office the following day, she was nauseated and vomiting on presentation. On exam, her vision was noted to be h.m., her corneal graft was trace edematous with folds, her anterior chamber was 3+ deep and clear without hypopyon. On examination of the wound, she was noted to have a large purulent mass under the conjunctiva overlying the tube with a mucoid discharge. No wound dehiscence was noted at that time.

Management Course

Because the patient was nauseated and vomiting, she could not complete her oral course of antibiotics. A CT scan was obtained, which revealed that she had inflamed sinuses and a localized periorbital cellulitis around the Baerveldt valve.

The patient was hospitalized and given 1 g cefazolin (initial dose, four doses daily thereafter during hospitalization). However, after the culture results were obtained she was switched to 1 g vancomycin every 12 hours for the next
2 days. She was also continued on topical gatifloxacin for eight doses daily while awake and on topical prednisolone using the same dosing schedule.

The patient was examined on a daily basis while in the hospital and was noted to have gradual improvement with resolution of the purulent mass under the conjunctiva and resolution of the pain and swelling involving the left eye. Post-treatment, small-wound dehiscence was noted.

After a 4-day course of IV antibiotics, oral antibiotics were started. She had gradual resolution of the cellulitis. The graft over the tube and the conjunctiva over the body of the tube were noted to thin, indicating pericardium graft melting. The patient was placed on high-dose vitamin C and vibramycin in order to slow the lytic process.

Two months after the infection had presented, a decision was made to perform a bleb revision using a scleral-patch graft and amniotic-membrane graft. The tissue was fragile and difficult to handle. One month post revision the tube body was noted to be poking through the conjunctiva.
The chamber was shallow and the eye was hypotonous.

The tube was removed and the chamber deepened. A new tube was placed with a supramid stent in the inferior nasal position. A corneal patch graft was placed using interrupted 9-0 nylon suture and AmnioGraft (Bio-Tissue, Miami, Fla.) sutured over top of the graft under the conjunctiva.

The patient healed well without recurrence of the tube exposure in the new site. The old site was well healed with residual patch graft still visible under the conjunctiva. She had excellent IOP, 12 mm Hg, at postop.

Discussion

Conjunctival erosion and tube exposure are significant risk factors for the development of endophthalmitis in eyes with glaucoma drainage devices.1 In this case, the stent acted as an impediment to a full blown case of endophthalmitis. The best way to prevent endophthalmitis is to preserve the intact conjunctiva over the tube.

A number of different tissue types (including donor sclera, cornea, fascia lata, dura matter and pericardium) have been used. Pericardium has been favored since it is processed prior to use. Recent evidence indicates that a scleral patch can melt, resulting in conjunctival erosion and endophthalmitis.2 More recently, the cornea has become a resource to cover the tube with the added advantage of facilitating laser suture lysis.3

Prompt repair of tube erosion is preventative. However, the fragile conjunctiva can be difficult to manage, especially in the setting of recent infection. As in this case, pericardium patch graft can be used with conjunctival advancement. Doubling the pericardium has been used successfully as opposed to a single layer. In cases were the conjunctiva is thin or fragile, AmnioGraft can be placed under the conjunctiva overlying the tube or the conjunctiva sutured around it over the patch graft.4 Tube position may also be a factor. The inferior nasal position may be less prone to conjunctival erosion and some surgeons prefer using the 12 o'clock position, rather than placing the tube superior and temporal.

As in this case, if an attempt at repair has failed, then it is recommended and appropriate that an alternative location be found with a new Baerveldt device. Alternatively, a smaller valved device, such as an Ahmed valve (New World Medical, Rancho Cucamonga, Calif.), can be used. 

Regine Pappas, M.D., is principal of Pinnacle Eye Center located in Melbourne, Fla. She can be e-mailed at rmpappas@aol.com.

REFERENCES

1. Krebs DB, Liebmann JM, Ritch R, Speaker M. Late infectious endophthalmitis from exposed glaucoma setons. Arch Ophthalmol. 1992;110:174-177.

2. King AJ,Azuara-Blanco A. Pericardial patch melting following glaucoma implant insertion. Eye. 2001;15:236-237.

3. Rojanapongpun P, Ritch R.Clear cornea graft overlying seton tube to facilitate laser suture lysis. Am J Ophthalmol. 1996;122:424-425.

4. Dua HS, Gomes JA,King AJ, maharajan VS The amniotic membrane in ophthalmology. Surv Ophthalmol. 2004;49:51-77.