Postoperative Complications and Management
Although meticulous surgical technique is important, the success of an incisional glaucoma procedure depends to a great extent on careful postoperative management (Fig 12-13). Many complications can arise during the early and late postoperative period, compromising the success of the surgery, vision, and ocular health (Table 13-4). Thus, timely identification of potential complications is imperative.
Overfiltration occurs when there is too little resistance to aqueous flow from the anterior chamber into the subconjunctival space. It is usually caused by inadequately tightened scleral flap sutures. Other causes include intraoperative flap buttonhole and proximity of the fistula to the edge of the flap. Overfiltration may be associated with an exuberant bleb (in the absence of a bleb leak) and a shallow anterior chamber. Treatment options include reducing topical steroids (to allow the development of subconjunctival fibrosis) and placing additional scleral flap sutures (Video 13-4). The development of hypotony maculopathy (optic nerve and/or retinal edema and radial macular folds causing a decline or distortion in vision) is an indication for intervention.
VIDEO 13-4 Transconjunctival scleral flap suturing at slit lamp.
Courtesy of Susan Liang, MD.
Bleb leaks can occur at any point in the postoperative course. In the early postoperative period, leaks most commonly occur at the incision site. Unrecognized buttonholes and flap suture erosion through the conjunctiva can also lead to leaks. They are often symptomatic (patients report experiencing excessive tearing) and can be found by performing a Seidel test (Video 13-5; see also Chapter 4). In addition to hypotony, patients with a leak may have a shallow or normal anterior chamber depth and a low-lying bleb. Untreated leaks can lead to early bleb fibrosis and infection.
VIDEO 13-5 Identifying a bleb leak.
Courtesy of Chandrasekharan Krishnan, MD.
There are several treatment options. Decreasing topical steroids can promote fibrosis and healing. Aqueous suppressants reduce the flow through the defect, allowing the leak to seal through epithelialization. Placement of an oversized contact lens can provide a scaffold for re-epithelialization and may also tamponade the leak. Suturing the site of the leak may be necessary if conservative measures fail.
Table 13-4 Complications of Trabeculectomy
Choroidal effusions can also occur at any time in the postoperative period when the IOP is low, with blebs of any size. Elderly patients with low IOP are more likely to develop choroidal effusions as compared to hypotony maculopathy (perhaps because of their greater scleral rigidity). The anterior chamber will be shallow, more so peripherally than centrally. Fundus examination discloses the classic grayish dome-shaped effusions, anchored in the region of the vortex veins.
Treatment includes use of cycloplegics to deepen the anterior chamber. If overfiltration or a bleb leak is the cause, decreasing steroids may be useful in promoting healing and fibrosis. If ciliary body inflammation (and aqueous hyposecretion) is the cause, increasing steroids is beneficial. Injecting viscoelastic into the anterior chamber can temporarily elevate the IOP and hasten recovery. If conservative management fails, the effusion can be drained in the operating room through posterior sclerotomies. The scleral flap is often reinforced at the same time to increase resistance to outflow (Video 13-6).
VIDEO 13-6 Scleral flap resuturing and choroidal drainage.
Courtesy of Lauren Blieden, MD.
Sclerostomy obstruction can occur at any point but is most frequent in the early postoperative phase (Fig 13-13). The condition is characterized by a low bleb, deep chamber, and elevated IOP. The sclerostomy may be blocked by a blood clot, fibrin, vitreous, or iris; gonioscopy is crucial to determine the cause of the obstruction. Laser iridoplasty or iridotomy can be used to manage iris tissue incarcerated in the sclerostomy. Tissue plasminogen activator can dissolve a blood clot quickly if needed.
Tight scleral flap sutures impair egress of aqueous humor, resulting in a low bleb, deep anterior chamber, and higher-than-desired IOP (Fig 13-14A). Moderate to firm digital ocular massage forces fluid through the flap, elevating the bleb and lowering the IOP. Determining the optimal time to cut 1 or more flap sutures can be a difficult balancing act (Fig 13-14B, C). If done too soon, overfiltration may occur; if done too late, the formation of fibrosis under the flap (from lack of flow) may result in inadequate long-term control of IOP.
Malignant glaucoma (also known as aqueous misdirection) and suprachoroidal hemorrhage can have very similar findings: shallow chamber, moderate to large bleb, and normal or high IOP (Fig 15-13). The chamber is very shallow centrally. Fundus evaluation (or B-scan ultrasonography if the view of the posterior segment is poor) is usually required to determine the cause of these findings. Treatment of suprachoroidal hemorrhage involves pain control and temporizing medical management of the IOP. Anticoagulant and antiplatelet therapy should be stopped if possible. Choroidal drainage should be delayed unless there is corneolenticular touch, intractable pain, or “kissing choroidals.”
Malignant glaucoma is treated with cycloplegics and medical management of the IOP. Attempts can be made to break the vitreous face with the Nd:YAG laser (through the pupil in a pseudophakic patient or through a peripheral iridotomy in a phakic patient). If these approaches are unsuccessful, vitrectomy is warranted, with particular attention to disruption of the anterior hyaloid.
Fibrosis most commonly develops in the subconjunctival space but can occur at the level of the scleral flap as well. Adequate flow through the scleral flap and into the subconjunctival space in the early postoperative period is important for long-term surgical success. Accordingly, control of fibrosis with topical steroids and subconjunctival antifibrotic agents (MMC, 5-FU) is of value. Conjunctival hyperemia in the postoperative period is a harbinger of subsequent fibrosis and necessitates the use of corticosteroid and/or antifibrotic therapy. Cutting or removing flap sutures increases flow and mitigates fibrosis. Transconjunctival needle revision (bleb needling; Video 13-7) can help disrupt fibrosis. A sharp-tipped instrument is introduced subconjunctivally to disrupt fibrotic tissue, allowing the formation of a more diffuse bleb.
VIDEO 13-7 Bleb needling.
Courtesy of Cynthia Mattox, MD.
Bleb-related infection (Fig 16-13) is a potentially vision-threatening complication after trabeculectomy, occurring in 1.5%–6.0% of patients. Patients typically present with tearing, irritation, pain, and/or blurry vision. Risk factors for infection include untreated blepharitis, presence of an inferior bleb, bleb leak, and thin-walled blebs (which tend to occur with localized blebs). The use of MMC and 5-FU is also a risk factor, as these agents are associated with a higher incidence of thin-walled blebs and bleb leaks. The formation of thin-walled blebs and bleb leaks can be mitigated by fornix-based trabeculectomies and diffuse application of the antifibrotic agent.
One proposed classification scheme divides bleb-related infection into 3 stages, although these stages represent a continuum of infection:
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stage 1: erythema around the bleb, bleb infiltrate
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stage 2: anterior chamber inflammation
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stage 3: hypopyon and/or intravitreal involvement
Stage 1 and stage 2 bleb-related infection (blebitis) can be treated with topical fluoroquinolones or fortified topical and subconjunctival antibiotics as needed. Stage 3, indicated by the presence of a hypopyon or intravitreal involvement (bleb-related endophthalmitis), warrants either a vitreous tap with injection of antibiotics or a vitrectomy. Patients with stage 1 and stage 2 bleb-related infection tend to fare well, while those with stage 3 tend to have poor visual outcomes.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.