Filtering Bleb Complications Treatment & Management

• Late leaking bleb and/or late bleb rupture: Thin blebs, especially after antimetabolites, are at risk for late leaks. They often are linked to, but not necessarily associated with, hypotony.

  • Thin blebs can show an obvious leak or a more subtle percolation (ooze) when tested with fluorescein.
  • Fluid can also pass transconjunctivally very slowly, thus being missed unless the observation of the fluorescein stained bleb is prolonged enough, while holding the upper lid to prevent blinking; pearls of aqueous can be observed to form on the conjunctiva in such cases, which can be described as "sweating" bleb.
  • In case of an excessively functioning filtering bleb causing side effects the following can be attempted, depending on the clinical features:
    • Palmberg mattress compression suture
    • Autologous blood injection
    • Continuous wave Nd:YAG laser application over fluorescein stained conjunctiva
    • Cryotherapy
    • Trichloroacetic acid coagulation
    • Excision of redundant bleb
    • Conjunctival grafting either free or sliding/pedunculated
    • Amniotic membrane, pericardium, dura, or scleral patch graft^[2]
    • Transconjunctival scleral flap suture^[3]
  • Surgical revision and repair is a reliable and definitive treatment. However, leaks can recur and/or the filtration effect can be lost with a subsequent rise in IOP.
• Infection

  • Early infection develops within the first week following surgery. Early infection is caused by the introduction of the infective agent at the time of the procedure and is not specifically related to bleb complications.
  • Late infection occurs weeks to months after surgery. Late infections probably are due to transconjunctival migration of microorganisms through leaks, holes, breaks, or weakened thin tissue. Thin blebs after the use of antimetabolites are a definite risk factor for late infections.
  • Blebitis
    • Diffuse bulbar hyperemia
    • Congestion around the bleb
    • Variable anterior chamber (AC) reaction
    • Discharge
    • Possible purulent material within the bleb
    • No vitreous involvement
    • Conjunctival swabs over the bleb for identification and culture
    • Topical fortified antibiotics every hour with subconjunctival antibiotics daily
    • AC tap depending on the presentation and on the clinical course
  • Endophthalmitis
    • Diffuse bulbar hyperemia
    • Congestion around the bleb
    • Variable AC reaction with hypopyon
    • Discharge
    • Possible purulent material within the bleb
    • Vitreous involvement
    • Conjunctival swabs over the bleb and AC tap for identification and culture
    • Vitreous tap for identification and culture and for intravitreal antibiotic injection (see Endophthalmitis, Postoperative)
    • Topical fortified antibiotics every hour with subconjunctival antibiotics daily
    • Early vitrectomy depending on the presentation and on the clinical course
• Hypotony

  • Hypotony is caused by the following:
    • Large overfiltering blebs, shown in the image belowLarge, extended, overfiltering bleb causes symptoms because of tear flow disturbances and ocular surface wetting.
    • Leakage of aqueous through conjunctival tears and holes
    • Leakage of aqueous through the retracted (fornix-based flap) or dehisced (limbus-based flap) edges of the conjunctival flap
  • Can be accompanied by shallow/flat AC and choroidal detachment
  • Management is to repair the cause.
  • Overfiltration, early in the postoperative period - The following can be attempted:
    • Firm patching, placing a small roll of cotton over the lid corresponding to the filtration area
    • Placement of a large bandage soft contact lens
    • Revision with further suturing of the scleral flap
  • Overfiltration, late in the postoperative period - The following can be attempted:
    • Palmberg mattress compression suture
    • Autologous blood injection
    • Continuous wave Nd:YAG laser application over a fluorescein stained conjunctiva
    • Cryotherapy
    • Trichloroacetic acid coagulation
    • Excision of redundant bleb
    • Conjunctival grafting either free or sliding/pedunculated
    • Amniotic membrane, pericardium, dura, or patch graft
• Circumferential blebs

  • Blebs, which are functioning well, can extend inferiorly even to 360°
  • Once the bleb starts to extend downward from the superior quadrants, its downward expansion is favored by the relative thinness of the Tenon layer laterally.
  • When bulging, these blebs can cause symptoms as they interfere with blinking and tear flow.
  • Management can include lubricants and tear supplements, as well as staged excision of the sectors of the conjunctiva, away from the functioning upper quadrant.
• Corneal dissecting blebs

  • The anterior edge of the bleb extends over the cornea within the epithelium, forming a white, nonvascularized, multiloculated, and spongy tissue, which can protrude for several millimeters. An example is shown in the image below. Corneal dissecting bleb, extending forward within the corneal epithelium.
  • The Bowman layer and the stroma remain intact.
  • This condition can cause symptoms when it interferes with blinking or tear flow, causes bubble formation, or irritates corneal nerves.
  • Management can include lubricants and tear supplements. If not effective, the part of the bleb lying over the peripheral cornea can be excised under topical anesthesia at the slit lamp or under a surgical microscope in the minor operating room. Simple excision without suturing or grafting is usually sufficient.
• Dellen

  • Corneal dellen develop in front of steep-walled blebs usually when placed either nasally or temporally.
  • The bulk of the bleb impedes the contact of the inner surface of the upper lid with the peripheral cornea.
  • Lubricants and tear supplements are indicated for management, and they need to be used intensively. Ointments and patching are the next levels of intervention. When symptoms persist, a Palmberg compression mattress suture usually is effective. Surgical revision is to be considered when all else fails.
• Decreased visual acuity

  • Severe complications, such as infections or prolonged hypotony, carry the most risk for a permanent decrease in visual acuity.
  • Visual function can be adversely affected by the following:
    • Intermittent astigmatism induced by the upper lid in case of hypotony
    • Induced astigmatism caused by the pressure of the upper lid on a large cystic bleb extending over the limbus; a cystic bleb is shown in the image below Cystic, thick-walled bleb, defined most commonly as a Tenon cyst.
    • Induced astigmatism caused by a scleral flap that is too tight or too loose
    • Ocular surface disturbances
    • Macular edema, chorioretinal folds

In cases of endophthalmitis, a vitreoretinal surgeon may be consulted.

Limitations on physical activity and/or any activity that will cause Valsalva-like effects are to be considered in cases of hypotony.