Late Complications of Glaucoma Surgery
Nathan M. Radcliffe
Gabriel Chong
Francisco Fantes
Paul F. Palmberg
INTRODUCTION
In most cases, glaucoma-filtering surgery is safe and effective at lowering intraocular pressure. However, this treatment is not always perfect. Some of the undesired outcomes of filtering surgery are caused by technical failures or by an undesirable wound healing response (Table 28-1). Reproducible, methodical, and safe surgical techniques combined with attempted modulation of the biologic response may minimize some of these undesired outcomes. Despite our best efforts, however, delayed problems can occur (Table 28-2).
The goal of this chapter is to review some of the more common delayed complications of glaucoma-filtering surgery and discuss possible treatment strategies. Some of the treatment strategies are more strongly established and have passed the test of time. Other procedures and alternatives are newer and may have helped one or more of the authors to solve some individual problems. The newer or somewhat infrequent procedures may not yet have passed the tests of rigorous research and time because of the rarity of the situations in which they have been applied.
TABLE 28-1. Factors That Can Influence Wound Healing | |||||
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TABLE 28-2. Undesirable Outcomes as a Result of a Vigorous or Inadequate Healing Response | ||||||||||||
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HYPOTONY
• Hypotony can result in reduced vision from corneal striae, maculopathy, choroidal effusion, and delayed suprachoroidal hemorrhages.
• It is often the result of insufficient scleral flap resistance that many times will require resuturing the flap in trabeculectomies performed with antimetabolites. Alternative therapies have also been described1,2,3,4; however, these therapies are probably less likely to be successful in cases in which antimetabolites have been used, or a rapid result is needed, such as patients with a flat chamber, maculopathy, or the so-called kissing choroidals. When there is overfiltration with a necrotic-looking scleral flap, sutures may not provide enough resistance to flow. In these cases, donor tissue may be needed as a roof to the flap to achieve the desired resistance. It is advisable to have donor tissue available whenever one is attempting to revise a scleral flap or to repair a leaking bleb.
• Chronic hypotony, which persists for at least 3 months, can lead to hypotony maculopathy and loss of vision.5 Dr. Palmberg employs a method using transcorneal sutures to treat hypotony at the slit lamp. The technique involves passing 10-0 nylon sutures through the cornea, through the scleral flap, and then back through the conjunctiva at the slit lamp with the objective of increasing resistance at the scleral flap to raise intraocular pressure (Fig. 28-1).
Hypotony Maculopathy
• Hypotony maculopathy is a condition in which folds in the choroid or retina, or both, involving the foveal region cause blurred vision in the setting of hypotony. The mechanism is probably scleral contraction.
• The maculopathy does not occur in all cases of hypotony, but is more likely to occur in eyes of patients who are young and myopic, and those with marked reductions in intraocular pressure.
• It is best to treat this condition quickly, because it can become permanent, although there are reports of success after years of involvement6 (Fig. 28-2A and B).
• The best therapy is prevention, such as the cornea safety valve incision as devised by Palmberg.7
• Palmberg also described a technique for bleb revisions to fix maculopathies, whereby two sets of sutures are added. The first set of two sutures adjusts the outflow from the flap to an intraocular pressure of 8 to 12 mm Hg. The second set is adjusted to an intraocular pressure of 20 to 25 mm Hg.7 It is important to keep in mind the possibility that donor tissue may be needed when revising a flap (see Fig. 28-2C and D).
TABLE 28-3. Causes of Altered Intraocular Pressure and a Flat Anterior Chamber | |||||||||
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Shallow and Flat Anterior Chamber
• Depending on the etiology, flat chambers can be associated with high or low intraocular pressures (Table 28-3; Fig. 28-3). With a postoperative flat or shallow chamber, the clinical history, examination, and intraocular
pressure guide the examiner in making the diagnosis.
pressure guide the examiner in making the diagnosis.
• The indications for draining a choroidal effusion include the following:
Flat chamber resulting in lens-corneal contact or significant iridocorneal contact that is likely to lead to permanent synechiae
So-called kissing choroidals (retina-retina contact between the choroidal swellings) to avoid fibrin adherence between the overlying retina
Persistence (after treating with cycloplegics or topical steroids)
• It is appropriate to observe these eyes for several weeks so long as neither of the first two conditions is present.
Strategies for Reformation of the Anterior Chamber
• Tamponade via pressure or Simmons’ shell or symblepharon ring: The strategy is likely to be more successful in surgeries without antimetabolites, and is to be used in situations of overfiltration.
• Viscoelastic injection into the anterior chamber: This strategy is more likely to have success in filters without antimetabolites.
• Resuturing the flap: This may end up being the definitive solution when antimetabolites were used.
Draining Choroidal Effusions
• A paracentesis is placed temporally (Figs. 28-4 and 28-5A).
• Conjunctival incisions are made at 4:30 and 7:30 meridians from 2 to 7 mm from the limbus, or a limbal peritomy from the 4 to 8 o’clock positions.
• A half-thickness radial incision of 2 mm is made, beginning 3 mm from the limbus as measured by calipers.
• The edge of the flap is grasped by a toothed forceps for countertraction.
• With a sharp blade, the incision is slowly and carefully deepened until the suprachoroidal space is opened (Fig. 28-5B).
• The incision is enlarged with a Kelly punch (Fig. 28-5C).
• If the incision is over a pocket of fluid, it will begin the outflow, which can be helped by infusing balanced salt solution through the paracentesis, lifting the edges of the flap, and rolling a cotton-tipped swab along the scleral surface.
• If the incision is not over a pocket of fluid and fluid is not mobilized to the incision, a cyclodialysis spatula can be used to separate the choroids gently from the scleral wall to obtain communication to an adjacent pocket of fluid. This dissection should be done extremely carefully, and not more than a few millimeters from the incision.
• Indirect ophthalmoscopy could be used at this time to look at the flattened retina. The anterior chamber should be deep, as well, and iridocorneal adhesions should be released with a cyclodialysis spatula if necessary.
• The conjunctival incisions should be closed, leaving the punched incisions open (Fig. 28-5D).
Delayed Suprachoroidal Hemorrhages
• A suprachoroidal hemorrhage is a condition in which bleeding occurs in the suprachoroidal space separating the uvea from the sclera. These hemorrhages can occur intraoperatively as well as in the postoperative period.
If bleeding occurs intraoperatively, the posterior pressure can cause extrusion of the contents of the eye (e.g., expulsive hemorrhage). The delayed suprachoroidal hemorrhages can be the result of de novo bleeding into the suprachoroidal space or of bleeding into a preexisting choroidal effusion.
• The risk factors include marked decompressions of the intraocular pressure, multiple
previous eye surgeries, myopia, previous vitrectomy, and systemic hypertension.
previous eye surgeries, myopia, previous vitrectomy, and systemic hypertension.
• A suprachoroidal hemorrhage often presents as sudden, severe pain associated with a brown-colored choroidal elevation in one side of the vitreous cavity. It is advisable to manage the patient with vitreoretinal surgery if possible.
• Serial B-scan ultrasounds are helpful to show the location of the hemorrhage and monitor the clot for lysis; this usually occurs 5 to 10 days after the onset of the hemorrhage.
• Many surgeons prefer waiting until the clot liquefies (lyses) before draining the hemorrhage. The technique is the same as described earlier for drainage of a choroidal effusion.
• Smaller suprachoroidal hemorrhages may reabsorb spontaneously in about 1 month with good visual results. While the clot is liquefying, the intraocular pressure should be controlled medically to the best degree possible.
• An extremely elevated intraocular pressure could force an earlier intervention.
REFERENCES
1. Akova YA, Dursun D, Aydin P, et al. Management of hypotony maculopathy and a large filtering bleb after trabeculectomy with mitomycin C: success with argon laser therapy. Ophthalmic Surg Lasers. 2000;31(6):491-494.
2. Marzeta M, Toczolowski J. Administration of autologous blood to a patient via intrableb injection as a method for treating hypotony after trabeculectomy. Klin Oczna. 2000;102(3):199-200.
3. Okada K, Tsukamoto H, Masumoto M, et al. Autologous blood injection for marked overfiltration early after trabeculectomy with mitomycin C. Acta Ophthalmol Scand. 2001;79(3):305-308.
4. Yieh FS, Lu DW, Wang HL, et al. The use of autologous fibrinogen concentrate in treating ocular hypotony after glaucoma filtration surgery. J Ocul Pharmacol Ther. 2001;17(5):443-448.
5. Azuara-Blanco A, Katz LJ. Dysfunctional filtering blebs. Surv Ophthalmol. 1998;43(2):93-126.
6. Delgado MF, Daniels S, Pascal S, et al. Hypotony maculopathy: improvement of visual acuity after 7 years. Am J Ophthalmol. 2001;132(6):931-933.
7. Palmberg P. Surgery for complications. In: Albert D, ed. Ophthalmic Surgery: Principles and Techniques. Vol. 1. London, UK: Blackwell Science; 1999.
 FIGURE 28-1. Transcorneal sutures. A. Diagram of the technique. (From Eha J, Hoffman E, Pfeiffer N. Graefes Arch Clin Exp Ophthalmol. 2008;246:869-874.) B. Photo montage of the effect of transcorneal sutures over time. |
 FIGURE 28-2. Hypotony. A. Dramatic example of hypotony causing folds in the choroid and retina involving the foveal region. B. Example of trace cystic changes and subtle folds in the internal limiting membrane in a patient with hypotony maculopathy as shown in optical coherence tomography. C. Intraoperative video still frame showing a cut piece of donor cornea being used to cover a flap. D. Intraoperative video still frame showing a compression suture of 10-0 nylon being used over the piece of donor cornea to increase the scleral resistance to aqueous outflow. ILM, internal limiting membrane; RPE, retinal pigment epithelium. |
 FIGURE 28-3. Shallow anterior chamber slit-beam photograph showing a shallow anterior chamber. There is significant iridocorneal touch; however, neither the pupillary border nor intraocular lens is in contact with the cornea. |
 FIGURE 28-4. Peripheral choroidal effusions. Fundus photograph showing peripheral choroidal effusions (left). |
 FIGURE 28-5. Repair of choroidal effusion. Intraoperative video still photographs of a repair of choroidal effusion. A. Paracentesis side port using a sharp point number 75 blade is made at the corneoscleral limbus. B. A sharp blade is used to gently enter the suprachoroidal space at the base of the partial-thickness radial scleral incision. C. Once the suprachoroidal space is entered, the incision is widened using a Kelly punch; at the base of the incision, a hole created by the punch can be seen. D. The conjunctival incision is closed using 7-0 Vicryl sutures; the sclerotomy is left open. |
BLEB LEAKS
• A bleb leak is a tiny hole in the wall of the bleb causing leakage of aqueous. This is a direct communication between the exterior world and the interior of the bleb. The use of intraoperative antimetabolites is a risk factor for the development of a bleb leak.
• The mechanism of a bleb leak is thought to be as follows. Ischemic blebs are stretched and surrounded by heavily scarred tissue, which limits the ability of the aqueous to flow beyond the scarred tissue. The bleb expands locally, producing a tractional hole when the tissue overreaches its maximal stretch.
• The bleb leaks are best detected by applying fluorescein to the surface of the bleb and viewing it under a slit lamp with a cobalt blue filter in place. A positive Seidel test consists of a change in the color of the dye to green-yellow, in response to the outflow of aqueous from the leak. Sometimes a leak can only be detected after applying gentle pressure to the globe.
• Leaks increase the risk of infection and endophthalmitis; therefore, early detection and management could be critical.1,2,3,4 The reported incidence of late postoperative bleb-related infections after a trabeculectomy ranges from 0.4% to 9.6% at 2 to 6 years.5,6 It is also estimated that blebitis occurs with an incidence of 5.7% per year, whereas the incidence of endophthalmitis ranges from 0.8% to 1.3% per year.5
• Careful surgical techniques during surgery are critical in decreasing the risk of bleb leaks. Special attention has to be paid to technique in the trabeculectomy—in suturing the conjunctiva; in the time, area, and washout of the antimetabolites; and to being methodical when applying laser suture lysis.7
Treatment
Conservative Management
• Following are some of the techniques described to manage wound healing in eyes with bleb leaks. These techniques have the advantage of sparing the patient from surgery. The disadvantage is that they are not always successful and leaks can recur. Although these treatments are not operative procedures, each has its own set of risks.
Use of 28-mm soft contact lenses for 2 weeks7
Use of butyryl methacrylate glue and a silicon disc7
Infusion of autologous blood into the bleb8
Application of compression sutures7
Pressure eye patching, oral carbonic anhydrase inhibitor, and topical autologous serum5
Chemical irritants (trichloroacetic acid, sodium nitrate)9
Cryopexy and diathermy10
Surgical Treatment
• Options
Closing the trabeculectomy with a scleral or corneal patch graft and replacing with a glaucoma drainage device (GDD)—in severe cases, corneal lamellar grafting has been described as a “final” solution to a dysfunctional bleb whereby the scarred conjunctiva and weakened spongy sclera are dissected away and replaced with round lamellar preserved donor corneal tissue.13
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