Filtering Bleb Complications 

Updated: Jan 08, 2015
Author: Carlo E Traverso, MD; Chief Editor: Hampton Roy, Sr, MD 

Overview

Background

The consequences of bleb-associated complications include the following, listed in order of potential morbidity:

  • Predisposition to or cause of infection

  • Unsatisfactory bleb function (ie, intraocular pressure [IOP] too low, IOP too high)

  • Dysesthesia

  • Decreased visual acuity

  • Loss of the globe, which can be the final outcome

Pathophysiology

The goal of glaucoma filtering surgery is to reduce IOP with surgery. The pressure can be too high or too low following the surgery.

Epidemiology

Frequency

United States

This condition is uncommon.

Mortality/Morbidity

Bleb complications can be classified according to their vision-threatening potential and impact on quality of life.

All bleb-related complications have infection/endophthalmitis as a possible consequence, with high morbidity.[1] Also, bleb failure with consequent rise in IOP or excessively low IOP are possible consequences.

The cost for the individual and the community in terms of discomfort, unplanned care, loss of work time, direct medical expenses, and decrease in visual function cannot be estimated and may be high.

Race

No racial predisposition exists.

Sex

No sexual influence exists.

Age

No influence of age exists.

 

Presentation

History

History includes previous filtration surgery for the management of glaucoma. Presentation varies remarkably depending on the complication being observed.

Physical

Clinical picture varies considerably depending on the complication. These eyes show evidence of filtration surgery in common, with a range of associated glaucomatous damage.

Causes

Causes may include buttonholes and tears, dehiscence, or retraction.

Conjunctival buttonholes and tears, dehiscence of the conjunctival incision, or retraction of the conjunctival edge are usually a result of suboptimal surgical techniques. Examples of these are shown in the images below.

Suboptimal suturing techniques can cause gaping of Suboptimal suturing techniques can cause gaping of the conjunctival incision.
Retraction of a fornix-based conjunctival flap. It Retraction of a fornix-based conjunctival flap. It can progress to uncover the scleral flap.

Care must be taken in handling the tissues, and meticulous suturing techniques need to be used. Attention to detail is key in the prevention of these problems.

Dehiscence and retraction are almost unavoidable when using absorbable sutures in conjunction with antimetabolites.

Each of the above events can cause an entire spectrum of bleb-associated complications (see Complications).

The most evident risk factor for late bleb leaks, bleb ruptures, and infections is the intraoperative or postoperative use of antimetabolites. After antimetabolites, blebs tend to be more ischemic and thinner, with progressive thinning and possible spontaneous rupture.

 

DDx

Differential Diagnoses

 

Workup

Laboratory Studies

For infections, full microbiological workup is necessary.

See Endophthalmitis, Postoperative.

Imaging Studies

Optical coherence tomography (OCT) is used to assess macular edema in cases of decreased visual acuity associated with hypotony.

Depending on the clinical picture, ultrasound B-scan can be useful to assess the vitreous cavity if endophthalmitis is suspected or present and to establish the retinochoroidal relationships in cases of hypotony.

Other Tests

Perform aqueous and vitreous taps in cases of infection.

Perform a Seidel test to look for leakage (see Surgical Care). Example results are shown below.

Seidel test. While holding the upper lid to avoid blinking during this evaluation, a dry fluorescein strip is moved over the conjunctival bleb, so as to smear it with dry fluorescein, which will appear very dark under blue light. As soon as the aqueous leaks, the color will turn to very bright yellow.
Fluorescein staining of the conjunctiva shows an o Fluorescein staining of the conjunctiva shows an obvious leakage of aqueous.
After fluorescein staining, aqueous is percolating After fluorescein staining, aqueous is percolating slowly, forming tiny droplets on the surface that mimic a sweating bleb.
 

Treatment

Surgical Care

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.[4] 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 below

    Large, extended, overfiltering bleb causes symptom Large, 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

It 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[5]

  • Placement of a large bandage soft contact lens

  • Revision with further suturing of the scleral flap[6]

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 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 a 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

Consultations

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

Activity

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

 

Medication

Medication Summary

Prophylactic antibiotics are not effective to prevent late endophthalmitis.

Antibiotics

Class Summary

Therapy must be comprehensive and cover all likely pathogens in the context of this clinical setting.

Vancomycin hydrochloride (Vancocin, Vancoled, Lyphocin)

Indicated for treatment of serious or severe infections caused by gram-positive organisms.

Ceftazidime (Ceptaz, Fortaz, Tazicef, Tazidime)

Third-generation cephalosporin with broad-spectrum, gram-negative activity; lower efficacy against gram-positive organisms; higher efficacy against resistant organisms. Arrests bacterial growth by binding to one or more penicillin-binding proteins.

Corticosteroids

Class Summary

Have anti-inflammatory properties and cause profound and varied metabolic effects. Corticosteroids modify the body's immune response to diverse stimuli.

Dexamethasone intravitreal implant (Decadron, AK-Dex, Alba-Dex)

Decreases inflammation by suppressing migration of polymorphonuclear leukocytes and reducing capillary permeability.

Prednisolone ophthalmic (AK-Pred, Delta-Cortef, Econopred)

Synthetic analog of naturally occurring glucocorticoid used to suppress the inflammatory response.

 

Follow-up

Further Outpatient Care

Specialist and subspecialist care is recommended, tailored to both the type and the severity of the complication.

Deterrence/Prevention

Conjunctival buttonholes and tears, dehiscence, and retraction of the conjunctival incision are usually a result of suboptimal surgical techniques.

Care must be taken in handling the tissues, and meticulous suturing techniques need to be used. Attention to detail is paramount in the prevention of these problems.

Dehiscence and retraction are almost unavoidable when using absorbable sutures in conjunction with antimetabolites.

The use of a larger area for the application of antimetabolites reduces the occurrence of small ischemic blebs, which are more prone to complications.

Complications

Potential complications include the following:

  • Loss of vision

  • Loss of bleb function

  • Hypotony

  • Loss of anatomical integrity of the globe

  • Phthisis

Prognosis

Prognosis is favorable with prompt treatment.

Patient Education

Instruct patients undergoing filtration surgery to report immediately to an ophthalmologist at any time after surgery if persisting redness, discharge, decreased vision, or pain occurs.