A 52-year-old black female who had advanced primary open-angle glaucoma presented with a 1-day history of conjunctival injection and mild discomfort in her left eye. This eye had undergone a trabeculectomy with mitomycin C (MMC) 6 years earlier and cataract extraction 3 years before presentation. Her visual acuity was 20/40 OS.
Slit-lamp biomicroscopy revealed an elevated, avascular bleb without leakage or infiltrates. There was mild conjunctival hyperemia with papillary reaction. One to two cells per high power field were visible in the anterior chamber, but the anterior vitreous was quiet. The IOP measured 9 mm Hg OS. The attending ophthalmologist diagnosed viral conjunctivitis, prescribed topical antibiotic therapy, and recommended re-examination the next day.
On the following day, the patient's symptoms were unchanged, but examination revealed increased conjunctival hyperemia and infiltrates in the bleb (Figure 1). Cellularity in the anterior chamber had increased (grade 3), and cells were also visible in the anterior vitreous (grade 1).
Figure 1. The patient's left eye was injected and had a focal, avascular, thin-walled bleb with a visible infiltrate.
The diagnosis made was bleb-related endophthalmitis. The treating physician performed aqueous and vitreous taps, administered intravitreal vancomycin and ceftazidime, and prescribed hourly topical, fortified tobramycin and vancomycin drops.
Comments on the Differential Diagnosis of a Red Eye After Trabeculectomy
RNW: What is blebitis, and how does one differentiate it from endophthalmitis?
CAG: Blebitis is an infection limited to the filtering bleb, whereas bleb-related endophthalmitis is an intraocular infection that includes the vitreous. Inflammatory cells may spill over into the anterior chamber in blebitis, but the vitreous is quiet. The presence of inflammatory cells within the vitreous is key for differentiating blebitis from bleb-related endophthalmitis.
RNW: Distinguishing between blebitis and endophthalmitis can be difficult. With blebitis, there may be cells within the anterior chamber, but there typically are no vitreous cells. At the other extreme, a large number of inflammatory cells within the vitreous clearly indicates the presence of endophthalmitis. In between these extremes, one often cannot be certain of the diagnosis, but differentiating between the two entities does have important therapeutic implications.
Comments on the Management of Blebitis and Bleb-Related Endophthalmitis
CAG: There is no consensus on the management of blebitis, and glaucoma specialists have a variety of practice patterns.1 My preferred treatment for blebitis is an hourly topical, fortified antibiotic (vancomycin and either gentamycin or ceftazidime). The prognosis for isolated blebitis is good.
JGC: If there is an infiltrate in the bleb, cells in the anterior chamber, or hypopyon and cells in the vitreous, I will proceed as for endophthalmitis. I will perform aqueous and vitreous taps and administer intravitreal antibiotics. In aphakic or pseudophakic eyes, because there may be less of a mechanical barrier to the spread of infection into the vitreous, my threshold for treating cases as endophthalmitis is even lower.
CAG: More cells may also spill into the vitreous in aphakic or pseudophakic eyes. The line differentiating these cells from vitreous infection is often not clearly demarcated. It is important, however, to have a high level of suspicion with all eyes that have injected blebs and intraocular inflammation. In eyes with small pupils, one may not be able to view the anterior vitreous clearly, and B-scan ultrasound may be helpful.
JGC: How useful are specimens from the anterior chamber tap in identifying the infectious agents?
RNW: Forster et al2 demonstrated more than 25 years ago that the yield of organisms from the anterior chamber tap is frequently less than the yield obtained from vitreous taps. Similar findings were reported subsequently in the Endophthalmitis Vitrectomy Study.3
Comments on Trabeculectomy Technique
RNW: Thin-walled, avascular blebs and leaking blebs are at increased risk of infection.4,5 How can a surgeon minimize the formation of these blebs?
CAG: A large subconjunctival dissection with a broad intraoperative application of an antimetabolite encourages the posterior flow of aqueous humor and the development of diffuse filtering blebs.
RNW: For more than a decade, I have dissected Tenon's tissue to obtain a large area for the application of an antimetabolite. During the past several months, I have been impressed by how the Blumenthal dissector (Katena Products, Inc., Denville, NJ) facilitates the dissection.
CAG: The intraoperative application of MMC often is associated with the formation of an avascular bleb and an increased risk of endophthalmitis,6 but avascular blebs can also develop after surgery with the intraoperative application of 5-fluorouracil. Using 5-fluorouracil rather than MMC, in conjunction with a large dissection/treatment area, may reduce the incidence of focal avascular blebs.
RNW: Paying attention to pre- and postoperative lid hygiene is another potential means for reducing the risk of postoperative infection. Identifying and treating lid-margin disease and dry eye in patients with thin-walled blebs, in particular, is likely beneficial. In addition, blebs that have a focal leak should be repaired.7 What about managing thin avascular blebs that have mild, diffuse oozing of aqueous humor?
CAG: There is no clear evidence that prophylactic antibiotics are effective, and I generally do not use them. Anyone with an avascular bleb like that should be made aware of the signs and symptoms of infection and know to seek medical attention immediately in the event of pain, decreased vision, or discharge.
FOLLOW-UP
The patient responded well to the combination of intravitreal and topical antibiotics. Her visual acuity has remained at 20/40 OS for 3 months since treatment.
Section editors Jonathan G. Crowston, MD, PhD, and Robert N. Weinreb, MD, are glaucoma specialists at the Hamilton Glaucoma Center, University of California, San Diego. Dr. Crowston is Assistant Professor of Ophthalmology. Dr. Weinreb is Distinguished Professor of Ophthalmology and Director. They acknowledged no financial interest in the products or companies mentioned herein. Drs. Crowston and Weinreb may be reached at (858) 534-8999; jcrowston@ucsd.edu.
Christopher A. Girkin, MD, is Director, Glaucoma Service and Optic Nerve Imaging Center, Department of Ophthalmology, UAB School of Medicine, Birmingham, Alabama. He acknowledged no financial interest in the products or companies mentioned herein. Dr. Girkin may be reached at (205) 325-8110; cgirkin@uab.edu.
Ivan M. Tavares, MD, is Senior Clinical Fellow at the Hamilton Glaucoma Center, University of California, San Diego, and he is a glaucoma specialist at the Vision Institute, Federal University of São Paulo, Brazil. He acknowledged no financial interest in the products or companies mentioned herein. Dr. Tavares may be reached at (858) 534-5334; itavares@glaucoma.ucsd.edu.
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2. Soltau JB, Rothman RF, Budenz DL, et al. Risk factors for glaucoma filtering bleb infections. Arch Ophthalmol. 2000;118:338-342.
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7. Burnstiein AL, WuDunn D, Knotts SL, et al. Conjunctival advancement versus non-incisional treatment for late-onset glaucoma filtering bleb leaks. Ophthalmology. 2002;109:71-75.
