Ophthalmology Dx: No Love For This Worrying Time Bomb


  • Figure 1. The patient first appeared with this infected bleb 5 months after undergoing trabeculectomy.

  • Figure 2. This magnified view shows the infected bleb in greater detail.

  • Figure 3. This image shows resolution of the condition after ophthalmologic treatments.

A  77-year-old patient visited the emergency department complaining of a red left eye, with discharge, that he had been experiencing for 2 days. His history was relevant in that he had undergone a combined cataract removal and glaucoma procedure, trabeculectomy, in his left eye 5 months earlier. The emergency department issued him erythromycin and advised him to visit an eye specialist the next day, if things did not improve. He was seen the next morning, explaining that “Last night my vision got blurry, and now my eye feels much worse.”

Upon exam, the patient was found to have acuities of 20/25 OD, and 20/50 OS, with no improvement upon pinhole. His right pupil responded to light normally, but his left eye had a sluggish reaction. On slit lamp exam, his right eye’s anterior chamber (AC) was normal, but for a mild cataract. In the left eye, he had 1+ cells in the AC, a cloudy bleb (Figures 1 and 2), a posterior chamber IOL, and 2+ cells in anterior vitreous.

The patient was diagnosed with an infected bleb and early endophthalmitis in his left eye. He was referred on an emergency basis to a retinal surgeon, who saw him that afternoon and treated him with intravitreal antibiotics. Following the treatment and hospital admission, the patient had total recovery (Figure 3).

A 2018 article published by the American Academy of Ophthalmology astutely referred to trabeculectomy as “a ticking time bomb.”1,2 The term was also used in a 1996 editorial in Ophthamology. It’s little wonder why authors keep revisiting this metaphor. Trabeculectomy...

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A 2018 article published by the American Academy of Ophthalmology astutely referred to trabeculectomy as “a ticking time bomb.”1,2 The term was also used in a 1996 editorial in Ophthamology. It’s little wonder why authors keep revisiting this metaphor. Trabeculectomy has the potential for complications, even years later. Once a bleb leaks, it loses its protective barrier and becomes vulnerable to outside pathogens.1 Early onset bleb leakage occurs in the first few weeks after surgery due to incomplete conjunctival closure, wound dehiscence, or an inadvertent opening in the conjunctival tissue.1 The surgeon will monitor for bleb leaks during the early postoperative time. After this, the eye is monitored routinely for glaucoma as well as any late bleb leaks or discharge, change in vision, and redness in the months, or even years, after surgery. At any later time, if problems occur in a glaucoma patient, the patient needs to be made aware that a serious infection could be causing the red eye. If the patient is first seen in an emergency department, their eye history needs to be discussed and an eye specialist contacted. The patient must then be referred immediately, to an ophthalmologist. This is not a routine eye red eye problem, but is a potentially blinding situation, if treatment is delayed. 

Late bleb leakage typically results from thin bleb tissue, a result of antifibrotic use. Clinicians frequently apply mitomycin C and 5-fluorouracil to prevent fibrosis and scarring. However, these agents may themselves wear away at the tissue, increasing the likelihood of future leaks, according to researchers who were interviewed for the 2018 article.1 These late bleb leaks can occur as early as 6 weeks after the procedure, and as late as several years or even decades after surgery. Research from 2015 provides the Kaplan-Meier estimated incidence at 5 years, which varies from 1.5% to 6.3% for blebitis, and from 1.1% to 7.5% for bleb related endophthalmitis.3 There are many clinical and histopathologic studies regarding the use of  mitomycin C in failed trabeculectomies, including a 1997 case that shows a patient with a leaking bleb 42 years after glaucoma surgery.4-7

Trabeculectomy may lower IOP, but the complications can be significant, and the incidence of blebitis and endophthalmitis may increase with patient age. Trabeculectomy is still used, depending on the target IOP needed, in a combined cataract and glaucoma surgery procedure. Minimally invasive glaucoma surgeries (MIGS) have gained in popularity, as it does not result in an exposed fragile bleb, but researchers have not yet had time to get long term MIGS results. Trabeculectomy is a much older surgery, and has excellent IOP lowering potential, but it also has a significant long-term risk of complications.7 With the potential for complications years after the procedure, it can be like planting a time bomb, and requires regular monitoring.

Matthew Garston, OD, is an adjunct professor at the New England College of Optometry and was a senior staff optometrist in the medical department at MIT for 43 years.


1. Mott M. A ticking time bomb: how to fix a leaking bleb. EyeNet. Published online November 2018. Accessed November 30, 2021.

2. Parrish R, Minckler D. “Late endophthlamitis”— filtering surgery time bomb? Ophthalmol. 1996;103(8):1167-1168. doi:10.1016/s0161-6420(96)30527-7

3. Kim E, Law S, Coleman A, et al. Long-term bleb related infections after trabeculectomy: incidence, risk factors and influence of bleb revision. Am J Ophthal. 2015;159(6):1082-1091. doi:10.1016/j.ajo.2015.03.001

4. Hutchinson AK, Grossniklaus HE, Brown RH,et al. Clinicopathologic features of excised mitomycin filtering blebs. Arch Ophthalmol. 1994:112(1):74-79.  doi:10.1001/archopht.1994.01090130084023

5. Yamamoto T, et al, The 5-year incidence of bleb related infection and its risk factors after filtering surgeries with adjunctive mitomycin C collaborative bleb-related infection incidence and treatment study 2. Ophthalmol. 2014;121(5):1001-1006. doi:10.1016/j.ophtha.2013.11.025

6. Zahid S, Musch D, Niziol LM, Lichter PR, for the Collaborative Initial Glaucoma Treatment Study Group. Risk of endophthalmitis and other long-term complications of trabeculectomy in the Collaborative Initial Glaucoma Treatment Study (CIGTS) Am J Ophthalmol. 2003;155(4):674-680. doi:10.1016/j.ajo.2012.10.017

7. Ciulla T, Beck A, Topping T, Baker A. Blebitis, early endophthalmitis, and late endophthalmitis after glaucoma-filtering surgery. Ophthalmol. 1997;104(6):986-995. doi:10.1016/S0161-6420(97)30196-1