BLEB INFECTION (BLEBITIS)

See 9.18, Blebitis.

INCREASED POSTOPERATIVE IOP AFTER FILTERING PROCEDURE

Grade of Shallowing of Anterior Chamber

• Peripheral iris–cornea contact.

• Entire iris in contact with cornea.

• Lens (or lens implant or vitreous face)–corneal contact.

NOTE Please be sure to differentiate anterior chamber shallowing grading from both the Shaffer grading classification of angle depth and the Van Herick method for angle chamber estimation, all of which use numerical systems for grading. See Appendix 14, Angle Classification.

Differential Diagnosis

(See Table 9.17.1.)

If the anterior chamber is flat or shallow and IOP is increased, consider the following:

• Suprachoroidal hemorrhage: Sudden onset of excruciating pain (commonly 1 to 5 days  after surgery), variable IOP (typically high), hazy cornea, and shallow chamber. See 11.27, Choroidal Effusion/Detachment.

• Aqueous misdirection/malignant glaucoma: See 9.16, Aqueous Misdirection Syndrome/Malignant Glaucoma.

• Postoperative pupillary block: See 9.15.2, Postoperative Pupillary Block.

If the anterior chamber is deep, consider the following:

• Internal filtration occlusion by an iris plug, hemorrhage, fibrin, vitreous, or viscoelastic material.

• External filtration occlusion by a tight trabeculectomy flap (sutured tightly, scarred, adherent due to subconjunctival hemorrhage).

• Occluded tube shunt (e.g., by iris plug, vitreous, hemorrhage, viscoelastic, capsular material) or increased IOP prior to tube ligature release.

• Obstruction of Schlemm canal and collector channels by blood after goniotomy procedure or MIGS implant.

Treatment

Initial gonioscopy to assist in diagnosis is essential before starting any treatment.

1. If the bleb is not formed and the anterior chamber is deep, light ocular pressure should be applied to determine if the sclerostomy will drain (Carlo Traverso Maneuver). In fornix-based procedures, take great care to not disrupt the limbal wound.

   NOTE If the sclerostomy is blocked with iris, any pressure on the globe is contraindicated due to potential for further iris incarceration.

    

2. Laser suture lysis or removal of releasable sutures may be indicated to increase filtration around the scleral flap.

3. Topical pilocarpine or slow intracameral injection of acetylcholine can pull the iris out of the sclerostomy if iris incarceration developed within the past 2 to 3 days. If this fails, and the sclerostomy is completely blocked by iris, transcorneal mechanical retraction of the iris may work. In rare cases, argon laser iridoplasty may be useful to pull the iris enough to restore filtration. If the sclerostomy is blocked with vitreous, photodisruption of the sclerostomy with a YAG laser may be attempted.

4. Blood or fibrin at the sclerostomy may clear with time or tissue plasminogen activator (10 μg) injected intracamerally may reestablish aqueous flow through the sclerostomy. Aqueous suppression can be utilized until blood has dissipated.

5. Iris-tube obstruction may be treated in a similar fashion as above.

6. A stent suture may be removed or ligature suture may be lysed to open a valveless tube, but care must be taken as the IOP may drop dramatically if the tube is opened prior to postoperative month one.

7. Additional medical therapy may be necessary if these measures are not successful. See 9.1, Primary Open-Angle Glaucoma.

8. For suprachoroidal effusion or hemorrhage, if the IOP is mildly increased and the chamber is formed, observation with medical management is indicated. Surgical drainage is indicated for persistent chamber flattening or IOP elevation, corneal–lenticular touch, chronic retinal fold apposition, and/or intolerable pain. If possible, delay drainage for at least 10 days in cases of suprachoroidal hemorrhage.

9. If the above measures fail, reoperation may be necessary.

LOW POSTOPERATIVE IOP AFTER FILTERING PROCEDURE

Low pressures (<7 mm Hg) can be associated with complications such as flat anterior chamber, choroidal detachment, and suprachoroidal hemorrhage. An IOP <4 mm Hg is more likely associated with additional complications including macular hypotony and corneal edema.

Differential Diagnosis and Treatment

1. Large bleb with a deep chamber (overfiltration): It is often beneficial to have a large bleb in the first few weeks after trabeculectomy. However, intervention is appropriate if it is still present 6 to 8 weeks after surgery, the patient is symptomatic despite conservative measures, IOP is decreasing, or the anterior chamber is shallowing. Treatment includes topical atropine 1% b.i.d., intracameral viscoelastic, and possibly autologous blood injection into the bleb. Observation is recommended if the IOP is low but stable, the vision is stable, and the anterior chamber is deep.

2. Large bleb with a flat chamber (Grade I or II): Treatment includes cycloplegics (atropine 1% t.i.d.) and careful observation. If the anterior chamber becomes more shallow (e.g., Grade I becoming Grade II), the IOP decreases further, or choroidal detachment develops, the anterior chamber may be reformed with a viscoelastic material.

3. No bleb with flat chamber: Check carefully for a wound leak by Seidel testing (see Appendix 5, Seidel Test to Detect a Wound Leak). If positive, aqueous suppressants, antibiotic ointment, bandage contact lens, patching, or surgical closure may be necessary. If negative, look for a cyclodialysis cleft (by gonioscopy and UBM) or serous choroidal detachments. Cyclodialysis clefts are managed by cycloplegics, laser or cryotherapy (to close the cleft), or surgical closure. Serous choroidal detachments are often observed, since they frequently resolve when the IOP normalizes. See 11.27, Choroidal Effusion/Detachment.

4. Grade III flat chamber: This is a surgical emergency and demands prompt correction. Office-based reformation with viscoelastic is appropriate. Surgical treatments include drainage of a choroidal detachment and reformation of the anterior chamber with or without revision of the scleral flap or tube, reformation of the anterior chamber with viscoelastic, and cataract extraction with or without other procedures.

COMPLICATIONS OF ANTIMETABOLITES (5-FLUOROURACIL, MITOMYCIN C)

Corneal and conjunctival epithelial defects, corneal edema, conjunctival wound leaks, bleb overfiltration, bleb rupture, scleral thinning and perforation, and increased risk of blebitis. 

COMPLICATIONS OF CYCLODESTRUCTIVE PROCEDURES

Pain, uveitis, decreased vision, cataract, hypotony, scleral thinning, choroidal effusion, suprachoroidal hemorrhage, sympathetic ophthalmia, and phthisis.

MISCELLANEOUS COMPLICATIONS OF MIGS

Hyphema, inflammation, malposition, iris injury, cyclodialysis cleft, Descemet tear or detachment.

MISCELLANEOUS COMPLICATIONS OF FILTERING PROCEDURES

Cataracts, corneal edema, corneal delle, endophthalmitis, uveitis, hyphema, and bleb dysesthesia (discomfort).

MISCELLANEOUS COMPLICATIONS OF TUBE-SHUNT PROCEDURES

Cataracts, corneal edema, endophthalmitis, hyphema, scleral perforation, diplopia, and tube/implant erosion or extrusion.