Blebitis

# Overview
Blebitis is the inflammation of the ocular bleb as a result of bacterial infection. It is a possible complication of a trabeculectomy performed to treat glaucoma. The causative pathogens are usually Staphylococcus or Streptococcus bacteria. Trabulectomy creates a point of possible infiltration in the bleb; the prolonged use of anti-metabolites following trabeculectomy increases the risk of bleb infection via cyst formation, epithelial wall thinning and erosion, and goblet cell depletion and decreased mucin production. Membrane deterioration, in conjunction with an inferior location for the bleb, creates a flow pathway for bacterial infiltration through the bleb's aqueous humor. Symptoms of blebitis include ocular pain, photophobia and loss of vision, intraocular pressure, and fluid discharge. Physical examination may reveal erythema and hyperemia of the affected eye, as well as thinning and whitening of the bleb. The presence of maculopathic purulent infiltrate can also be found upon physical exam. The mainstays of therapy for blebitis are fortified topical antimicrobial and antibacterial agents, as well as topical corticosteroids. With treatment, the prognosis for blebitis is good. Without treatment, blebitis can result in bleb-related endophthalmitis, leading to a much worse prognosis, including permanent vision loss and death. Blebitis is very rare; the incidence in the United States was estimated to be 550 per 100,000 individuals (.55%) from 2007-2011.

# Historical Perspective
Blebitis was officially identified by Dr. R.H. Brown in 1994 to classify bleb-infection not associated with the vitreous.

# Classification
There is no diagnostic classification schema for blebitis. However, blebitis is considered Stage I of the bleb-related infection classification system.

## Bleb-related Infection Classification

# Pathophysiology

## Pathogenesis
The pathogenesis of blebitis is characterized by the infiltration of staphylococcus and streptococcus bacteria into the bleb following trabeculectomy. The removal of the trabecula and adjacent structures creates a point of infiltration for pathogenic bacteria. The prolonged use of anti-metabolites following trabeculectomy increases the risk of bleb infection. Anti-metabolite drug use results in epithelial thinning, which heightens the risk of infiltration..
Additional pathogenic factors include:
- Post-operative goblet cell depletion decreases the amount of protective mucin.
- Inferior placement of the bleb heightens the risk of infection by the increased risk of leakage, providing a flow pathway for pathogenic bacteria to travel from the lacrimal lake to the bleb.
Lack of protection from the eyelid for inferior bleb placements contributes to infection risk.
- Lack of protection from the eyelid for inferior bleb placements contributes to infection risk.

## Gross Pathology
On gross pathology, maculopathic purulent infiltrate, edematous erythema, hyperaemia and hypopyon are characteristics of blebitis.

## Microscopic Pathology
On microscopic histopathological analysis, goblet cell-depletion and epithelial thinning are characteristic of blebitis. Observation of the basement layer of conjunctival epithelial cells may demonstrate thinning, missing segments, or total absence.

# Causes
Blebitis may be caused by bacterial infection, predominantly Staphylococcus spp. and  Streptococcus spp.  Less commonly,Corynebacterium, Pseudomonas aeruginosa, and Nocardia have been isolated in cases of blebitis.

# Differentiating Blebitis from Other Diseases
Blebitis must be differentiated from other diseases that cause ocular erythema and hyperaemia, as well as pain, pressure, loss of vision, and photophobia.

# Epidemiology and Demographics
From 2007-2011, the incidence of blebitis in the United States was approximately 550 per 100,000 individuals.

## Age
Blebitis patients are usually less than 40 years old. Blebitis is also commonly seen in African American patients older than 40 years old and Mexican Americans older than 60 years old, due to the higher incidence of the precursory glaucoma surgery.

## Gender
Males are more commonly affected with blebitis than females.

## Race
African-Americans are more commonly affected with blebitis than other races. Inuit are more prone to blebitis due to the higher incidence of glaucoma in that population.

# Risk Factors
Common risk factors in the development of Blebitis include:
- Undergoing trabeculectomy for glaucoma
- Experiencing a bleb-leak
- Persistent use of anti-fibrotic topical agents
- Being male
- Being young
- Being African-American
- Experiencing recurrent bacterial conjunctivitis
- Inferior location of the filtering bleb
- Use of contact lenses
- Immunocompromise

# Natural History, Complications and Prognosis

## Natural History
Blebitis will require topical antibiotic therapy to resolve. Without treatment, blebitis may lead to bleb leakage and bleb-related endopthalmitis. Recurrence of infection and blebitis is likely without treatment.

## Complications
Without treatment, a possible complication of blebitis is endophthalmitis.  Endophthalmitis is caused when the pathogen causing blebitis, previously limited to the bleb, spreads past the anterior chamber of the eye and into the vitreous body.

## Prognosis
With treatment, the prognosis for blebitis is good. Risk of permanent vision loss is minimal with effective therapy.
Without treatment, the prognosis for blebitis is worse due to the increased risk of developing bleb-related endophthalmitis.

# Diagnosis

## Symptoms
Symptoms of blebitis may include:
- Ocular pain of the filtering bleb
- Excessive sensitivity to light
- Vision loss
- Intraocular pressure
- Fluid discharge

## Physical Examination
Physical examination may be remarkable for:
- Hyperemia in the affected eye
- Erythema of the affected eye due to presence of hypopyon
- Thinning of the bleb epithelium
- Whitening of the bleb
- Presence of maculopathic purulent infiltrate

## Laboratory Findings
A positive test for staphylococcus or streptococcus bacteria is diagnostic of blebitis.
- This is obtained via a culture and gram stain of the aqueous humor, swabbed from the surface of the bleb.
- Polymerase chain reaction (PCR) testing of the aqueous humor will reveal bacterial infection.

## Imaging Findings
There are no imaging findings associated with blebitis.

## Other Diagnostic Studies
Physical examination and microscopic histopathological analysis of suspected blebitis is sufficient for diagnosis.

# Treatment

## Medical Therapy
The mainstays of therapy for blebitis are fortified topical antimicrobial and antibacterial agents:
- fluoroquinolone
moxifloxacin
gatifloxacin
- moxifloxacin
- gatifloxacin
- chloramphenicol
- aminoglycoside
- vancomycin
- cephalosporin
Topical corticosteroids are often used in conjunction with antimicrobial therapy.

## Surgery
Surgery is rarely indicated for blebitis for cases such that the bleb displays positive Seidel-test results for leakage.
- Surgery will be performed to repair the bleb but is only indicated when the chance of reinfection is eliminated.

## Prevention
Effective measures for the primary prevention of blebitis include those that minimize the possibility of ocular bacterial infection following a trabeculectomy:
- Minimizing use of topical corticosteroids to prevent bleb-leakage that predisposes blebitis.
- Avoiding prolonged use of topical antibiotics beyond the prescribed time period post-trabeculectomy.
- Avoiding inferior or nasal placement of the bleb to reduce the risk of leakage.