Bleb-associated endophthalmitis is a late-onset intraocular infection that follows filtering glaucoma surgery, and it differs from typical postoperative endophthalmitis in that the risk never fully goes away, sometimes appearing years after the original trabeculectomy.
The thin, avascular bleb created by antimetabolite use is both what makes the surgery work and what leaves a lasting portal for bacteria to enter the eye.
Why the Risk Persists
A functioning filtering bleb is thin-walled and often relatively avascular, especially after mitomycin C or 5-fluorouracil use, and this same thinness that allows good filtration also makes the bleb more permeable to surface organisms.
Unlike routine postoperative endophthalmitis, which clusters in the days after surgery, bleb-associated infection can occur at any point in the life of the bleb, and the annual risk, while low for any given year, accumulates over a patient’s lifetime.
Risk Factors
- Inferior or nasal bleb location, which is more exposed to tear film debris than a superior bleb
- Bleb leak or a thin, cystic, avascular bleb appearance
- Antimetabolite use during the original surgery, particularly mitomycin C
- Blepharitis, conjunctivitis, or chronic ocular surface disease
- Contact lens wear over or near the bleb
- Younger age at the time of surgery, since a longer lifetime of bleb exposure raises cumulative risk
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From Choroida — the team behind this siteBlebitis Versus Bleb-Associated Endophthalmitis
Infection can be confined to the bleb itself, known as blebitis, or can spread into the vitreous cavity as bleb-associated endophthalmitis.
- Blebitis presents with a white, opaque bleb, mild anterior chamber reaction, and preserved vision
- Bleb-associated endophthalmitis adds vitreous involvement, marked pain, significant vision loss, and often a hypopyon
- The organisms responsible tend to be more virulent than in typical postoperative endophthalmitis, with Streptococcus and Haemophilus species reported more often, which explains the frequently aggressive course
Because blebitis can progress rapidly to full endophthalmitis, any patient with a red, painful eye and a history of trabeculectomy needs urgent assessment rather than a routine appointment.
Diagnosis
Diagnosis is clinical, based on the appearance of the bleb, anterior chamber, and vitreous.
- Slit-lamp examination of the bleb for a leak, using a Seidel test with fluorescein
- Assessment of the vitreous for haze, which distinguishes blebitis from endophthalmitis
- Vitreous and aqueous sampling for culture when endophthalmitis is suspected, following the same principles used for other forms of postoperative endophthalmitis
- B-scan ultrasonography when the view is obscured
Management
Blebitis Without Vitreous Involvement
Intensive topical antibiotics, often fortified, along with topical corticosteroids once infection is controlled, are usually sufficient when the vitreous is clear.
Close follow-up is essential, since the situation can worsen quickly.
Bleb-Associated Endophthalmitis
Vitreous involvement is treated as an emergency with intravitreal antibiotics, following the same principles established for postoperative endophthalmitis, and vitrectomy is considered for severe cases with poor vision at presentation.
Systemic antibiotics are sometimes added given the more virulent organism profile typically seen with bleb infections.
After the Acute Episode
Bleb leaks and thin, at-risk blebs may need surgical revision once the infection is controlled, to reduce the risk of recurrence.
Patients should be counseled about ongoing risk and the importance of prompt reporting of any new redness, discharge, or pain around the bleb, for the rest of the bleb’s functional life.
Prevention
- Treating blepharitis and ocular surface disease proactively in patients with a filtering bleb
- Avoiding contact lens wear that overlies the bleb
- Prompt repair of bleb leaks
- Patient education on warning signs, since early presentation improves outcomes substantially
Prognosis
Outcomes are worse than for typical postoperative endophthalmitis, reflecting both the more virulent organisms involved and the sometimes delayed presentation when symptoms are mistaken for minor irritation.
Prompt recognition and treatment give the best chance of preserving vision, and it is why patients with any filtering bleb are told, indefinitely, to treat a new red painful eye as an emergency.
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From Choroida — the team behind this siteReferences
- Busbee BG. Bleb-associated endophthalmitis: clinical characteristics and visual outcomes. Curr Opin Ophthalmol. 2005;16:170-174.
- Waheed S, Ritterband DC, Greenfield DS, Liebmann JM, Seedor JA, Ritch R. Bleb-related ocular infection in children after trabeculectomy with mitomycin C. Ophthalmology. 1997;104:2117-2120.
- Yamamoto T, Kuwayama Y; Collaborative Bleb-related Infection Incidence and Treatment Study Group. Interim clinical outcomes in the collaborative bleb-related infection incidence and treatment study. Ophthalmology. 2011;118:453-458.
- Kangas TA, Greenfield DS, Flynn HW Jr, Parrish RK 2nd, Palmberg P. Delayed-onset endophthalmitis associated with conjunctival filtering blebs. Ophthalmology. 1997;104:746-752.
