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Ophthalmology – Blebitis
Blebitis is an infection involving a filtering bleb, which is a subconjunctival reservoir intentionally created during glaucoma surgery (such as trabeculectomy) to allow aqueous humor drainage. It is important to distinguish blebitis from bleb-associated endophthalmitis (BAE), a more severe condition in which infection extends into the vitreous. Blebitis is limited to the anterior segment, whereas BAE involves deeper intraocular structures and carries a much worse prognosis.
This condition most commonly occurs following trabeculectomy, especially when antifibrotic agents like mitomycin C are used. The incidence varies, with blebitis occurring in approximately 5.7% of such cases, while BAE is less common but more serious. Risk factors include inferiorly located blebs, thin or avascular blebs, bleb leaks, prior infections such as conjunctivitis or blepharitis, repeated surgical manipulation, and chronic antibiotic use. These factors compromise the natural protective barrier of the conjunctiva, allowing microorganisms to penetrate.
The pathophysiology differs depending on timing. Early-onset infections (within one month of surgery) are typically due to contamination during surgery, often involving less virulent organisms. Late-onset infections occur months to years later and are usually caused by more aggressive organisms that can penetrate compromised bleb tissue or enter through leaks. Common causative organisms include Staphylococcus epidermidis and Staphylococcus aureus for blebitis and early infections, while Streptococcus species, Haemophilus influenzae, and gram-negative bacteria are more common in late-onset BAE.
Patients with blebitis usually present with a red eye, mild discomfort, and possibly decreased vision. In contrast, BAE often presents abruptly with severe pain, photophobia, discharge, and rapid visual loss. On examination, blebitis is characterized by localized conjunctival injection around the bleb, a milky or cloudy appearance of the bleb, and sometimes purulent material. Anterior chamber inflammation may be present. The key distinguishing feature of BAE is vitreous involvement, often accompanied by hypopyon, which should be considered endophthalmitis until proven otherwise.
Diagnosis is primarily clinical but may be supported by additional testing. Slit-lamp examination is essential, and B-scan ultrasonography may be required if the posterior segment view is obscured. Cultures from purulent material, anterior chamber taps, or vitreous samples may help identify the causative organism, although treatment is often initiated empirically due to the urgency of the condition.
Management requires prompt and aggressive treatment. Blebitis is typically treated with intensive topical fortified antibiotics such as vancomycin and tobramycin or cefazolin, administered frequently. Mild cases may be treated with high-frequency topical fluoroquinolones. In contrast, BAE is a medical emergency requiring intravitreal antibiotics, typically vancomycin combined with ceftazidime (or amikacin if needed). Repeat intravitreal injections may be necessary, and vitrectomy is often considered. Adjunctive oral antibiotics may be used, and corticosteroids may be cautiously introduced to control inflammation.
Close follow-up is critical, often requiring daily or even multiple daily evaluations, as progression from blebitis to BAE can occur rapidly. Patients must be educated to seek immediate care for symptoms such as redness, pain, or blurred vision.
The prognosis of blebitis is generally good with early treatment, especially when caused by less virulent organisms. However, bleb-associated endophthalmitis carries a poor prognosis despite aggressive therapy, with many patients experiencing significant vision loss. Complications include bleb failure, intraocular scarring, glaucoma progression, cataract formation, retinal detachment, and, in severe cases, loss of the eye.
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