Postoperative Management Following Filtration Surgery
Mahmoud A. Khaimi, MD and Marcos Reyes, MD
The role of trabeculectomy in achieving control of glaucoma is well established.1 Management of the patient following filtration surgery for glaucoma is the most important step in obtaining long-term success in control of intraocular pressure (IOP) and preservation of vision. Advances in surgical techniques; careful patient selection; recognition of high-risk patients; the common use of antimetabolites that are used intraoperatively, postoperatively, or both; and awareness of the early signs of bleb compromise have all improved long-term surgical success rates.
The intraoperative advances that have evolved since the introduction of the operating microscope for almost all glaucoma surgery have clearly enhanced the exact technique of tissue manipulation and alignment. Serious problems, such as failure to recognize a thin fragment of Descemet’s membrane, which were not easily assessed with loupes, are more easily recognized using the operating microscope. The advent of microsurgical instrumentation, extremely sharp blades and scissors, precise cautery or diathermy (electrocautery), delicate tissue handling, and fine suture materials have resulted in improved surgical techniques that enhance the possibility of surgical success.
The recognition and management of early postoperative complications, including wound leaks, choroidal detachment, flat chambers, and compromised blebs, have been facilitated by the absolute necessity of examining patients with the slit-lamp biomicroscope and indirect ophthalmoscopy with attention to the finest details of recently operated eyes.
Recognizing a satisfactory postoperative bleb appearance and overall ocular course is essential. Recognizing impending bleb failure and ultimate loss of IOP control is critical to successful postoperative management following filtration surgery. The early observations of bleb compromise with vascular injection and inflammation of Tenon’s capsule and the episclera are important. Observing a diffusely quiet and noninflamed bleb with tiny microcysts and an IOP in the high single digits or low teens is the ultimate goal of all glaucoma surgeons. However, recognizing a slight but definitive vascular ingrowth into the base of the bleb, decreased size and evidence of flattening of a previously functioning bleb, and a gradual IOP increase alerts the surgeon that bleb failure is occurring. Intervention at this stage is absolutely critical to long-term bleb survival. There are many techniques and options available to the surgeon at this time; frequent postoperative visits are necessary to institute the appropriate techniques to shepherd the bleb through this critical time.
In the late stages of bleb evolution, when the ocular condition is stable and the IOP is controlled, the risk of infection and late aqueous leaks must be adequately conveyed to the patient and the patient’s family. A delay in follow-up examination when early bleb infection or early endophthalmitis is present could result in blind ness. Alerting the patient to the symptoms and signs of infection and/or leak is an absolute necessity and is the sur geon’s responsibility. The symptoms and signs of ocular infection should be reviewed at all patient visits, and the patient should be encouraged to seek ophthalmic assessment at the earliest suggestion of ocular infection.
PREVENTION OF COMPLICATIONS
The discontinuation of topical agents that may create vascular congestion and ocular inflammatory reactions can be considered 3 to 5 days preoperatively.
Evidence of lid infection or inflammation should be treated before filtration surgery is contemplated. Patients with underlying uveitis should be receiving topical corticosteroids preoperatively with or without a course of oral steroids (physician dependent), and those with neovascular glaucoma should have undergone an adequate course of panretinal photocoagulation to decrease the fibrovascular reactive state. More recently, intravitreal injection of anti–vascular endothelial growth factor medication has been shown to more quickly and dramatically reduce the neovascularization and should be considered in all cases of neovascularization in addition to panretinal photocoagulation. These carefully planned preoperative steps aid in promoting the successful outcome of filtration surgery.
Gentle handling of ocular tissues is an integral part of the surgical management of glaucoma patients. Using smooth or cusped forceps when handling conjunctiva and Tenon’s capsule prevents multiple tiny perforations and prevents the crushing of tissue that occurs with toothed or serrated forceps, both of which can promote the release of inflammatory mediators that increase scarring.2
The immediate use of hemostasis with unipolar diathermy or wet-field bipolar cautery is essential to prevent blood and blood products that stimulate inflammation from permeating the periocular space. When blood is absorbed by Tenon’s tissue, it often can be removed only by excision. Immediate cautery is advised to minimize blood in the subconjunctival space when bleeding oc curs.
Additional intraoperative therapeutic modalities have become an essential part of filtration surgery to minimize postoperative complications, particularly fibrosis, scarring, and bleb failure. The common use of mitomycin C (MMC) in concentrations ranging from 0.2 to 0.4 mg/cc for 2 to 4 minutes has become a routine adjunct to glaucoma filtering surgery, and it is the rare case in which it is not used.3–7 Although now less commonly used, 5-fluorouracil (5-FU) was the initial antimetabolite tested and used to prevent postoperative fibrosis. Studies8 showed the use of postoperative 5-FU also decreased the failure rate of patients when used in a standard protocol or with modifications.9,10 The long-term complications of antimetabolite usage are late bleb thinning result ing in chronic leaks, an increased incidence of blebitis, bleb-related endophthalmitis, and the potential of bleb necrosis and sloughing. Efforts to minimize these potential complications have included decreased application time of antimetabolites, decreased concentration of applied antimetabolites, and more diffuse application of antimetabolites at the time of surgery.
Efforts to achieve tight trabeculectomy flap closure with subsequent laser suture lysis or a releasable suture that provides firm flap apposition and better control of aqueous egress result in a high proportion of well-formed anterior chambers and reasonable early postoperative IOPs. This suturing technique combined with meticulous conjunctival closure (as in the example of a limbal-based trabeculectomy closure whereby a single running-locking closure or double closure involving Tenon’s capsule first and a conjunctival closure second) has been facilitated with fine tapered needles and absorb able suture material (Vicryl, Ethicon, Inc). The capacity to reduce wound leaks with tight conjunctival closure has resulted in significantly fewer flat anterior chambers with hypotony and sub sequent choroidal detachment and fewer prolonged flat anterior chambers.
EARLY POSTOPERATIVE MANAGEMENT
The critical period of postoperative management of filtration surgery occurs in the following 3 phases:
- The early postoperative course of approximately 1 to 7 days
- The mid-postoperative course, between 1 week and 3 months
- The late postoperative course, 3 months and longer
On the first postoperative day, routine assessments are made of the anterior chamber depth; the character, extent, and elevation of the bleb; conjunctival wound closure and integrity; IOP; and the posterior pole.
Assessment of Flat Anterior Chamber
Wound Leaks
When a shallow or flat anterior chamber is present during the first postoperative week, wound leaks are often responsible. The wound leak is almost always accompanied by a low IOP (0 to 6 mm Hg) and must be evaluated with a moistened fluorescein strip used to paint both the conjunctiva of the bleb and the conjunctival wound. A 2% solution of fluorescein can also be used. With the patient looking down, the 2% fluorescein is applied to the conjunctival surface in the region of the conjunctival incision and the entire surface of the bleb. Using either the fluorescein strip or the 2% solution, the physician must immediately examine this region with a cobalt blue filter on a standard biomicroscope. A leak is present if cascading darker aqueous with fluorescent edges is observed as the fluid runs from the wound leak. This is popularly called a positive Seidel test. The entire bleb surface should then be methodically examined, with particular attention to the area of the conjunctival wound and the area over the sclerectomy. A large buttonhole or a very tiny bleb perforation can result in significant aqueous flow and profound anterior chamber shallowing.
When a leak is detected, some advocate the use of aqueous suppressants, beta-blockers, and/or carbonic anhydrase inhibitors (CAIs). These agents decrease aqueous flow and allow conjunctival epithelial cells to slide to seal or diminish the leak. The use of a firm pressure patch is a time-honored remedy for a flat anterior chamber associated with a wound leak. However, this therapy can exacerbate lenticular-corneal touch and can even precipitate the active development of lens opacification.
Figure 61-1. Conjunctival advancement. Limbus-to-limbus dissection of the vascular conjunctiva at the border of the leaking avascular bleb.
Figure 61-2. Conjunctival advancement. Complete posterior undermining of Tenon’s to achieve mobile conjunctiva.
Figure 61-3. Conjunctival advancement. End closure using the Weis closure designed for fornix-based closures.
Figure 61-4. Conjunctival flap pedicle. (Reprinted with permission from Donald U. Stone, MD.)
If the leak is still present after 1 or 2 days of aqueous suppressant therapy and the chamber remains shallow, suturing the leak under biomicroscopic observation with the appropriate microvascular needle (9-0 or 10-0 Vicryl) can effectively close the leak and reestablish the normal anterior chamber architecture. If a wound leak persists despite these efforts, and no improvement is observed, a definitive operating room procedure involving deepening of the anterior chamber, choroidal tap if necessary, and wound repair or complete bleb revision may be indicated.
Management of Wound Leaks
Wound leaks that develop in thin conjunctival tissue close to the limbus and sclerectomy site can be effectively managed in many different ways. If the leak is small, topical antibiotics, artificial tear therapy (± topical lubricating or antibiotic ointment), and observation, alone or in combination with aqueous suppressant, may be adequate. In other cases, a large soft contact lens (18 to 24 mm) that serves to tamponade the leak may be necessary.11,12 The contact lens may be left in place for up to 10 to 14 days. The rigid glaucoma (Simmons) shell is most effective when used early in managing friable conjunctival tissue with multiple holes. Autologous tissue glues13 have also been reported to be a useful adjunct and a nonsurgical alternative to managing wound leaks. If the wound does not close after a trial period of conservative therapy, then surgical closure is recommended. Surgical revision usually consists of conjunctival advancement (Figures 61-1 through 61-3),14 conjunctival rotational flap (Figures 61-4 and 61-5), or if needed a conjunctival autograft.15 The use of amniotic membrane16 to assist in the surgical revision of a persistent wound leak has also been reported to be another option; however, its use has not matched the success rate of conjunctival advancement.
Figure 61-5. Conjunctival flap closure. (Reprinted with permission from Donald U. Stone, MD.)
Figure 61-6. Large kissing choroidal effusions.
TABLE 61-1. INDICATIONS FOR CHOROIDAL TAP
| Lens-cornea touch (axially flat anterior chamber) | Choroidal tap should be performed within 24 hours of lens-cornea touch |
| Corneal edema | Associated with very shallow anterior chamber |
| Prolonged peripherally flat anterior chamber (> 5 days) | In the absence of anterior chamber deepening |
| Appositional or kissing choroidals | Choroidal tap should be performed within 24 to 48 hours |
| Prolonged hypotony, low bleb (> 7 days) with a moderate to large choroidal effusion |
Choroidal Detachment
If the anterior chamber is shallow or flat with a normal or low IOP and no demonstrable wound leak, choroidal detachment (Figure 61-6) should be considered. Fluid collects in the suprachoroidal space and results in forward movement of the lens iris diaphragm with anterior chamber shallowing and flattening.17,18 The serous effusion is easily recognized when the pupil is dilated and mound-like elevations of the peripheral retina and choroid are seen. The most common clinical scenario is an IOP reading below 6 mm Hg, a shallow anterior chamber, no lenticular-corneal touch, and large choroidal effusions. In the absence of a significant indication to perform surgical drainage (choroidal tap), choroidal detachment can be treated conservatively with cycloplegic-mydriatics, topical steroids, and observation. If there is evidence of corneal edema and lenticularcorneal touch as well as a failing bleb, increasing inflammation, rising IOP, and retinal apposition kissing choroidals (see Figure 61-6), then drainage of the suprachoroidal space and anterior chamber reformation are advised.17
In the absence of indications to drain the suprachoroidal space, the anterior chamber gradually deepens as the supra choroidal fluid is absorbed when the IOP rises to more normal levels (Table 61-1). Observation and medical management are usually effective in treating this disorder.
Suprachoroidal Hemorrhage
A much more serious complication of filtration surgery is the development of a suprachoroidal hemorrhage. This often dramatic complication usually occurs within the first week after filtration surgery and is usually associated with postoperative hypotony. (Note that in effort to prevent this occurrence, cycloplegics should be initiated whenever there is hypotony from any cause [eg, leak, overfiltration, inflammation]). A suprachoroidal hemorrhage is heralded by the sudden onset of severe pain that is diagnostic when associated with profound choroidal detachment, a shallow anterior chamber, and a highly elevated IOP.19,20 After the acute event, the eye frequently becomes inflamed. The patient may have an inordinate amount of pain before the blood is drained from the suprachoroidal space. A waiting period of 7 to 10 days following a suprachoroidal hemorrhage is advised for the fibrinolytic response of fluid to liquefy the clot and allow for more effective evacuation of the suprachoroidal space and retinal and choroidal flattening.21 The risk of suprachoroidal hemorrhage is greater in patients with nanophthalmos, glaucoma associated with increased episcleral venous pressure (eg, Sturge-Weber syndrome), high myopia, aphakia or pseudophakia, and in vitrectomized patients, in the presence of elevated blood pres sure, advanced arteriosclerosis, bleeding disorders, and following the hypotony associated with tube-shunt surgery. At the time of suprachoroidal fluid drain age, using vitrectomy techniques with the instillation of air, intraocular expandable gases, or silicone oil are all options available if deemed appropriate by the retina surgeons to decrease the incidence of rebleeding and to tamponade the choroid and retina in their anatomic positions. Inflation of the bleb and evaluation of wound leaks should be performed during evacuation of the supra choroidal space.
R. Rand Allingham, MD
A choroidal tap is performed to reform the anterior cham ber and drain suprachoroidal fluid (effusion or blood in the case of a suprachoroidal hemorrhage). If the eye is extremely soft, we prefer to use a peribulbar block. Local anesthetic is placed subconjunctivally in the quadrants to either side and the furthest away from the filtering bleb.
If the original paracentesis cannot be found or cannulated, a new beveled paracentesis is made. The paracentesis should be made slowly with a very sharp blade in order to avoid a rapid entry into the anterior chamber, which could result in damage to the iris or lens. Grasping the horizontal rectus muscle on the same side as the paracentesis with 0.5-mm forceps can help stabilize the eye and reduce corneal wrinkling while performing the paracentesis. Using a 27-gauge cannula, the anterior chamber is re formed with balanced salt solution. The cannula tip must be through the cornea and in the anterior chamber before infusing fluid to prevent the stripping of Descemet’s membrane.
A horizontal conjunctival incision is made 3 to 6 mm from the limbus in the inferonasal or inferotemporal quadrant (away from the filtering bleb). Small blood vessels are gently cauterized prior to making the sclerotomy. The 2- to 3-mm radial sclerotomy is centered 3 to 4 mm from the limbus. We prefer to use a No. 15 Bard-Parker (Katena Eye Instruments) or No. 67 Beaver blade to make the sclerotomy because they are sharp enough to incise the sclera, but not so extremely sharp as to cut through the choroid on contact. Sharper blades can be used, but there is increased risk of penetrating the choroid and inadvertently entering the vitreous cavity. Clear to yellowish-tinged fluid often drains spontaneously once the incision is carried into the suprachoroidal space. Once the fluid flow slows, the tip of a 0.5- to 1.0-mm cyclodialysis spatula can be carefully inserted into the suprachoroidal space in a circumferential direction (parallel to the limbus). The spatula is removed and re inserted in the opposite direction. The anterior chamber is reformed periodically when the eye softens. The eye should not be allowed to become too soft in order to reduce the possibility of suprachoroidal hemorrhage. This cycle of anterior chamber reformation and fluid drainage is repeated until no further fluid drains from the sclerotomy. The anterior chamber is then reformed with special emphasis on reforming the filtering bleb. The eye pressure required to elevate the filtering bleb may be quite high to break conjunctival adhesions to episclera.
Once the anterior chamber has been reformed and the choroidal effusions have been drained, the sclerotomy openings are left open, and the conjunctiva is closed with 10-0 absorbable suture. Subconjunctival dexamethasone phosphate 8 to 12 mg is injected inferiorly. Atropine and antibiotic ointment are applied to the eye. The eye is gently patched and an eye shield placed.
Pupillary Block
Pupillary block is another cause for formation of a peripherally shallow or flat anterior chamber in the early postoperative period. Pupillary block may occur in the presence of normal or elevated IOP. The inability of aqueous to pass from the posterior to anterior chamber results in the forward movement of the peripheral iris and closure of the drainage channel. Pupillary block occurs when there is a peripheral iridectomy that is not patent, when there are adhesions of the iris to the lens (posterior synechiae) with resultant iris bombé, or with an anterior chamber lens (without a peripheral iridectomy) that prevents aqueous movement into the anterior chamber. Therapy with cycloplegic-mydriatics sometimes resolves pupillary block. However, a laser iridectomy is curative and advisable. In the presence of localized compartments of block, multiple iridectomies are suggested.
Malignant Glaucoma
The final differential diagnostic category of a shallow to flat anterior chamber during the early postoperative period is characterized by an IOP elevated to the high-normal or much higher levels and is associated with malignant glaucoma or aqueous misdirection.22 Aqueous misdirection results from posterior movement of aqueous into the vitreous cavity that forces the vitreous forward with resultant lens-iris diaphragm displacement and closure of the drainage channel angle. Hyperopic eyes with chronic angle closure following filtration surgery are most at risk. However, pseudophakic or aphakic eyes with an impermeable anterior hyaloid face are also at risk of developing this uncommon symptom complex.23
Malignant glaucoma may respond to medical management with CAIs (oral or topical), mydriatic-cycloplegics, and beta-blocking agents with reestablishment of the anterior chamber and an IOP decrease. If medical management is not successful, yttrium-aluminum-garnet (YAG) laser disruption of the anterior hyaloid face and posterior capsule can immediately and effectively deepen the anterior chamber and lower the IOP.24 If phakic patients do not respond to medical therapy, the neodymium (Nd):YAG laser may be attempted if a view of the ciliary processes can be obtained through a peripheral iridectomy or dilated pupil. This view is often difficult to obtain, and injury to the crystalline lens can occur. Surgical therapy for aqueous misdirection is penetration or removal of the anterior hyaloid face and penetration of the posterior vitreous with aspiration of liquid vitreous with a needle or vitreous cutting instrument.25
Figure 61-7. Iris incarceration of the sclerectomy site.
Early Bleb Evaluation
Careful observation of the bleb in the early postoperative period is extremely important. A diffuse non vascular, slightly elevated bleb with diffuse microcysts and an appearance of succulence that involves a superior portion of the globe is an encouraging observation following filtration surgery. Recognizing blood under the bleb, a flat vascularized bleb, or a very localized elevated bleb26 during the early postoperative period is a very poor prognostic sign and requires aggressive management. Little can be done for blood under the bleb, but blood and blood products that seal the trabeculectomy flap or hyphema and a blood clot in the sclerectomy respond dramatically to an intracameral or subconjunctival injection of tissue plasminogen activator. Dosages from 6 to 25 μg (10 μg/0.l cc) have been documented, but lower doses27,28 such as 12.5 μg or less are recommended to avoid hyphema. This procedure can be done at the biomicroscope through a paracentesis and can be repeated if necessary.29 The frequent use of topical steroids and cycloplegics can minimize the inflammatory response that occurs when blood is present in the subconjunctival or intraocular space.
If the bleb is flat and vascularized and the anterior chamber is formed with a normal or elevated IOP, obstruction of aqueous flow into the bleb is likely. Determining the site of obstruction is essential, and gonioscopy is the most effective method of evaluating the internal structures that are obstructed. Gonioscopy is essential for evaluating all postoperative bleb complications because the obstruction site can only be determined by careful examination. If there is evidence of obstruction by a Descemet’s flap, iris (Figure 61-7), ciliary body, or vitreous, laser intervention is often helpful. The argon laser can remove pigmented uveal tissue or blood products from the sclerectomy site. In other situations, an Nd:YAG laser can remove clear membranes or cut adherent uveal tissue that is not amenable to argon laser therapy.
Figure 61-8. Scleral flap suture status post-laser suture lysis. Laser energy is applied to either the posterior or anterior end of the suture.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
