• Ophthalmic Pearls

    Pearls April 2004

    Written By: Scott Blackmon, MD, and R. Rand Allingham, MDEdited by Ingrid U. Scott, MD, MPH, and Sharon Fekrat, MD

    In order to consider trabeculectomy surgery a success, multiple management issues must be addressed in the postoperative period. A thorough understanding of postoperative management of filtering surgery is required in order to obtain the target IOP while obtaining a diffusely elevated, microcystic, avascular bleb, whether or not antifibrotics have been used intraoperatively.

    Topical Medications

    Topical corticosteroids generally, prednisolone acetate 1 percent reduce inflammation and scarring, which improves the flow of aqueous through the sclerostomy and flap to elevate the filtering bleb. Steroids improve the intermediate and long-term postoperative IOP control.

    At our institution, we typically use topical steroids every two hours while the patient is awake for at least the first week or two postoperatively, unless there is a contraindication for example, a conjunctival buttonhole or bleb leak. Steroids are tapered over an eight- to 12-week period depending on clinical response or longer if inflammation persists. In the absence of severe uveitis or other inflammatory processes, systemic corticosteroids are rarely required.

    Topical antibiotics—we prefer ciprofloxacin 0.3 percent Ciloxan—are administered four times a day for two weeks and then discontinued. A simpler approach is to instruct the patient to use the antibiotic drops until the bottle is empty. If there is a bleb leak or the patient requires a bandage contact lens, antibiotics should be given until the bleb leak has stopped or the contact lens is removed.

    Some ophthalmologists routinely use antibiotic ointment at night for the first seven to 10 days after surgery. Potential options include erythromycin and bacitracin.

    The use of antibiotics for long-term prophylaxis as in the case of thin-walled blebs is controversial, but most feel that prophylactic treatment for leaking i.e., Seidel-negative filtering blebs does not reduce the risk of blebitis or endophthalmitis significantly and may select for resistant organisms.

    Cycloplegics are generally used in phakic patients. The main purpose of cycloplegia after trabeculectomy is to assist in the maintenance of anterior chamber depth in patients who are phakic. They may also reduce ciliary spasm for pain control postoperatively. Atropine 1 percent or scopolamine 0.25 percent are among the options. The typical frequency of use is once or twice daily for the first several days after surgery. Once the IOP is greater than 5 to 7 mmHg and the anterior chamber is quiet, cycloplegia may be discontinued.

    5-Fluorouracil

    Although it is occasionally used intraoperatively, 5-fluorouracil 5-FU is most often used in the postoperative period to reduce subconjunctival fibrosis. There is a clear indication for 5-FU injections in high-risk cases, including neovascular glaucoma, prior failed filtering surgery and uveitic glaucoma. Use of 5-FU may be helpful in cases of impending bleb failure; the signs of this may include flattening of the bleb, decreased microcyst formation and increased vascularization encroaching on the bleb, particularly when the bleb is becoming marginated and cystic.

    Postoperative subconjunctival 5-FU injections remain a helpful adjunct for eyes that have received mitomycin C MMC intraoperatively and for eyes that have been given 5-FU intraoperatively, as well as for cases where no intraoperative antimetabolites have been administered at all.

    We prefer to use a tetracaine pledget for local anesthesia before injecting subconjunctival 5-FU. Injections are placed in the inferior subconjunctival space. In order to reduce the chance of conjunctival hemorrhages, we often give phenylephrine 2.5 percent topically and perform all injections at the slit lamp. The number of 5-FU injections to administer depends on clinical response and toxicity. However, it is not uncommon to give three to seven injections in the postoperative period when active fibrosis is present.

    Use of 5-FU is not without risk. Bleb leaks, postoperative hypotony and an increased incidence of endophthalmitis are associated with antimetabolite use. The most common complication is corneal epithelial toxicity, which usually precludes the further use of 5-FU, at least until the cornea heals. In cases where corneal toxicity is early or where frequent injections are anticipated, a large-diameter bandage soft contact lens may be considered.

    Laser Suture Lysis


    With the use of laser suture lysis LSL, the ophthalmologist can titrate the postoperative IOP in order to avoid both hypotony and failure of the bleb see “Laser Suture Lysis Technique”. The goal of LSL is to improve fluid flow through the scleral flap; thus, the slit-lamp appearances of the bleb and, to a lesser extent, IOP, are considerations for performing LSL.

    The risks of hypotony, shallow or flat anterior chamber or even suprachoroidal hemorrhage are greatest when LSL is performed in the first few postoperative days. Therefore, LSL should be avoided on the first postoperative day in most cases. A good general rule of thumb is to cut no more than one suture per day in order to reduce the risk of hypotony or of a shallow anterior chamber.

    LSL is most effective if performed within two weeks of surgery in non-MMC cases. After this point, the scleral flap is often fibrosed into its final position. However, cutting sutures even months postoperatively can lower IOP significantly in some cases, particularly when intraoperative MMC has been used.

    Importantly, the use of 5-FU and LSL are independent of one another and may be performed on the same day. Digital pressure three to four times per day may be used as a supplement after LSL to help improve fluid flow.

    Follow-Up


    Frequent follow-up of any patient who has received filtering surgery is required in order to detect the early signs of bleb failure while it can still be reversed. All patients should be seen on the first postoperative day. If IOP is adequate and the filtering bleb appears intact without leakage, patients may be reexamined in five to seven days. If there is concern regarding bleb appearance, or IOP is elevated, more frequent follow-up is indicated.

    If there is hypotony, choroidal effusion or a bleb leak on the first postoperative day, the patient should return to the clinic every few days until the situation stabilizes. When there is increasing vascularity, 5-FU injections should be considered early and frequently, as needed. As a general rule, patients should return three to seven days following every 5-FU injection. After LSL, the patient should return in one week, assuming there is good IOP reduction after a suture is cut.

    Complications

    Numerous potential complications can occur after a trabeculectomy, ranging from mild to vision-threatening. It is important to inform the patient of the signs and symptoms of potentially serious complications. Some of the more serious complications include overfiltration, flat anterior chamber, bleb leak, hypotony, choroidal detachments serous or hemorrhagic, filter failure, blebitis and endophthalmitis. Patients should be told to notify their ophthalmologist immediately if they experience increasing pain, redness or decreased vision.


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    Dr. Blackmon is an ophthalmology resident and Dr. Allingham is associate professor of ophthalmology and chief of the glaucoma service; both are at Duke University.

     

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    Laser Suture Lysis Technique



    Informed consent

    Topical anesthetic placed in eye

    Lens: Hoskins lens preferred

    Laser: Argon; diode

    Spot size: 100 micrometers less likely to cause thermal injury or conjunctival buttonhole than 50 µm spot size

    Duration: 0.10 seconds

    Power: 300–800 mW although 300– 400 mW usually is sufficient

    800-1500 mW may be required if thick Tenon’s capsule or surgery several weeks previously

    IOP check one hour after LSL

    If 5-FU injection on same day, perform after LSL and subsequent IOP check