glaucoma

Co-Manage Glaucoma Surgery

KATHY YANG-WILLIAMS, O.D. F.A.A.O., Seattle Wash.

Be aware of the postoperative care involved in these three procedures, so you can allay patients' fears and ensure optimal outcomes.

In order for you to provide your glaucoma patients with the best postoperative care, you must be knowledgeable of the possible outcomes associated with each of the most common types of glaucoma surgery and how to treat patients who present with these outcomes.

1 LASER TRABECULOPLASTY (LTP)

In this procedure, the surgeon directs a laser beam into the trabecular meshwork using a gonio-lens placed on an anesthetized eye. The purpose: to facilitate the flow of aqueous fluid out of the eye in order to decrease intraocular pressure (IOP) in those open-angle glaucoma patients who cannot achieve target IOP with maximally tolerated medical therapy, who have adverse side effects to topical therapy or who aren't compliant with their eyedrops.

Before laser trabeculoplasty, the surgeon gives the patient a drop of topical steroid and a drop of an alpha agonist to reduce the risk of a postoperative IOP spike. Immediately after the surgery, the surgeon instills a second drop of the alpha agonist. Then, you or the surgeon should prescribe a steroid eyedrop q.i.d. for one week to alleviate anterior chamber inflammation.

Co-management of LTP occurs infrequently because this procedure is typically straightforward, making complications a rarity. Therefore, the post-op period for this procedure is 10 days, as opposed to 90 for most other ocular surgeries. Typically, however, a postoperative visit occurs one-week after the surgery.

The possible adverse outcomes of laser trabeculoplasty:

► Temporary or permanent elevation in IOP. The patient's IOP should be the same as it was prior to surgery or slightly better when he presents to you for the one-week post-op visit. Keep in mind, however, that the maximum IOP-lowering effect typically doesn't materialize until four to six weeks after the surgery. For this reason, have the patient maintain his customary eyedrop regimen, and schedule a second follow-up visit for three to five weeks later.

If the patient's IOP is elevated during the postoperative period, consider adding another glaucoma medication or appropriately adjusting his usual topical medications until the effect of the LTP (a decrease in IOP) materializes. If the patient has a moderate IOP elevation, schedule a follow-up visit for within three to five days. If the elevation is mild, schedule a follow-up for one-week later to reassess his IOP.

► Iritis. If the patient displays this condition at the one-week postoperative visit, extend topical steroid use for another week at the same q.i.d. dosing schedule. Then, have the patient return for follow-up in one week, at which time the patient's inflammation will have subsided.

Laser trabeculoplasty can fail to facilitate aqueous flow and lose its effectiveness through time. If the patient is unable to achieve success with this procedure, investigate the use of other glaucoma medications and/or other glaucoma surgeries, such as trabeculectomy. (See "What's on The Horizon," below.)

2 LASER PERIPHERAL IRIDOTOMY (LPI)

In this procedure, the surgeon employs a laser to create a small hole in the peripheral iris of primary-angle-closure glaucoma patients or patients who have narrow or occludable angles. The purpose: To resolve the iris' forward bowing, opening the eye's angle so that aqueous fluid can flow into the eye's anterior chamber and enter the trabecular meshwork for drainage. This procedure breaks an angle closure attack or prevents angle closure. Primary angle closure glaucoma is an acute condition requiring LPI on an emergent basis.

As with post-laser trabeculoplasty, you or the surgeon should prescribe a topical steroid q.i.d. for approximately one week to quell anterior chamber inflammation. Typically, a post-op visit occurs one-week after LPI.

Possible adverse outcomes of laser peripheral iridotomy:

► Iritis. If the patient presents with iritis, as with laser trabeculoplasty, extend post-op steroid use for another week at the same q.i.d. dosing schedule. Then, have the patient return for follow-up, so you can re-evaluate anterior chamber status.

► Elevation of IOP. Aside from an iritis-induced IOP increase, release of iris pigment or red blood cells from localized bleeding can elevate IOP. These cells can block the trabecular meshwork and reduce outflow. If the patient's IOP is high as a result of this, consider adding more glaucoma medications until his IOP has normalized. The timing of the next follow-up visit depends on the degree of IOP elevation. If the patient presents with mild IOP elevation, for instance, schedule him for follow-up in one week.

► Corneal abrasion due to contact laser lens. If the patient presents with this outcome, prescribe a mild antibiotic ointment q.i.d. until the defect heals. Or, use a bandage contact lens with a topical antibiotic eyedrop q.i.d. and a topical non-steroidal anti-inflammatory eyedrop q.i.d. Then, have the patient return for follow-up within 24 hours and every two to three days, so you can assess the healing process. Alternatively, you can prescribe a pressure patch with an antibiotic ointment for 24 hours to heal the abrasion if the patient can function with one eye covered.

►Inadvertent corneal or retinal laser burn. This is a highly rare occurrence. No treatment is necessary, however. Simply note it in the patient's medical record.

► Non-patent iridotomy. The patient may not achieve patency if the iris tissue is too dense or if hemorrhage occurs during LPI. In these cases, refer the patient back to the surgeon, so he can repeat the procedure.

►Late closure of the iridotomy. If the iridotomy closes from excessive scar formation, refer the patient back to the surgeon, so he can repeat the LPI.

Figure 1: diffuse bleb with minimal injection post-trabeculectomy with deep anterior chamber.

► Narrow angle. In some patients who undergo an LPI, their angle is still too narrow post-surgery. This creates an ongoing risk for angle closure and prevents you from performing a dilated fundus exam to evaluate the internal structures of the eye. If your patient presents with this outcome, he may require additional glaucoma surgery, such as iridoplasty or gonioplasty—a procedure in which the surgeon places large diameter laser burns adjacent to the iris root to draw the iris tissue out of the angle.

3 TRABECULECTOMY (GLAUCOMA FILTERING SURGERY)

In this operation, the surgeon creates a partial thickness flap in the sclera and removes a small piece of scleral and trabecular meshwork tissue from the drainage angle to create a channel. The purpose: to enable aqueous fluid to escape from the anterior chamber and flow into a "pocket," or filtering bleb, created between the conjunctiva and sclera. This bleb bypasses the poorly functioning trabecular meshwork, and the venous system absorbs the fluid, improving aqueous outflow and lowering IOP. Advanced glaucoma patients who haven't been able to obtain IOP control via medication and the aforementioned procedures might undergo this operation.

After this surgery, you or the surgeon should prescribe a topical antibiotic q.i.d. for one to two weeks prophylactically. Also, prescribe a topical steroid for q1h to q2h use initially and then taper through the next eight to twelve weeks to decrease inflammation of the anterior chamber, scleral flap and conjunctiva. The final prescription: a topical cycloplegic used q.d. to b.i.d. for the first few weeks to reduce pain and relax the ciliary muscle, to deepen the anterior chamber and prevent contact between the lens and the cornea.

Schedule follow-up appointments for every one to two days if the post-op IOP is extremely low, significant hyphema is present or the anterior chamber is very shallow. Other adverse complications can result from these post-op outcomes, and timely intervention can prevent serious consequences. (I discuss management of these possible outcomes later.) Otherwise, a follow-up check is necessary four to seven days after the surgery and then weekly for the first month.

Possible adverse trabeculectomy outcomes:

► Ocular hypotony (with or without wound leak). IOP following trabeculectomy is usually low, ideally in the 8mm Hg to 12mm Hg range. An IOP of 0, however, isn't unusual, especially if the patient has a wound leak or if over-filtration occurs.

To check for a wound leak, instill fluorescein dye near the conjunctival incision line. In addition, carefully inspect the bleb for a positive Seidel sign due to conjunctival buttonhole or tear. If the patient's IOP is extremely low, perform a pressure Seidel to enable the expression of aqueous fluid from the wound leak. To do this, use your fingers to slightly press against the globe through the eyelid to the side or opposite to the site of the surgery. You don't want to push so hard that the patient will have wound damage, so exercise caution when applying pressure.

If ocular hypotony develops following surgery due to a wound leak, interventions may include pressure patching; the use of aqueous suppressants to decrease flow of aqueous through the conjunctival defect (any dosage and duration should be effective); reduction in topical steroids; or the application of an oversized bandage contact lens (as large as 22.0mm). Prescribe the contact lens to put pressure in the wound leak's area, reduce outflow of aqueous, and to reduce rubbing from the lid over the conjunctiva, allowing the conjunctival defect to heal. Alternatively, you may apply a pressure patch similar to that used for treatment of a corneal abrasion. Have the patient continue with his topical antibiotic therapy q.i.d. to reduce the risk of wound-leak induced endophthalmitis in the anterior chamber. Also, advise hypotony patients to avoid activities that induce Valsalva maneuver, such as heavy lifting, as this can cause a suprachoroidal hemorrhage.

Persistent wound leaks may require referral to the surgeon for repair. The surgeon can repair smaller defects in-office or repair them with cyanoacrylate glue or trichloracetic acid. Large defects require a return to the operating room for suturing. Some defects may require a bleb revision with conjunctival resuturing.

If the patient has over-filtration (i.e. the absence of a wound leak) and can tolerate hypotony (meaning no reduction in vision), prescribe a topical cycloplegic for q.d. or b.i.d. use until the patient's IOP increases to a safe level or adverse side effects from cycloplegic use (light sensitivity, for instance) prevent the patient from continuing use. Examine patients who have well-tolerated chronic ocular hypotony every one to three months. Refer patients unable to tolerate cycloplegic use, who develop a flat anterior chamber, or who experience reduced vision from hypotony maculopathy (chorioretinal folds in the macula) back to the surgeon, so he can determine whether additional procedures are necessary to increase IOP. The surgeon may try to induce scarring in the bleb by performing an autologous blood injection, cryotherapy or laser photocoagulation to the bleb surface. Alternatively, the surgeon may elect to revise the bleb in the operating room and place additional scleral-flap sutures in an effort to slow the passage of aqueous through the surgical drainage pathway.

► Significant hyphema. Mild cellular reaction of the anterior chamber isn't uncommon. In some cases, however, patients can present with mild blood pooling in the anterior chamber e.g. 1mm or 2mm. Often, this resolves on its own. But, large amounts can cause trabecular obstruction with elevated IOP. If a large amount of blood is present in the anterior chamber and the patient's IOP climbs too high, blood could be forced into the cornea causing blood staining with the potential for vision loss. This would require a corneal transplantation.

If your patient presents with significant hyphema and elevated IOP that doesn't respond to topical glaucoma medications, refer him back to the surgeon, so he can consider an anterior chamber washout. If the IOP remains low and the chamber is deep, watch the patient every two to three days while maintaining a program of topical steroid eyedrops every q1h to q2h and a cycloplegic agent b.i.d. to q.i.d. until the blood is gone.

Figure 2: encapsulation of bleb with localized dome-like elevation and telangiectatic conjunctival vessels.

► Hypopyon. If the patient presents with pus in the anterior chamber, this is a sign of endophthalmitis, or infection, inside the eye. This is the most serious complication following glaucoma surgery.

Blebitis or bleb infection can occur as a localized infection of the bleb more commonly associated with a late wound leak, the use of anti-metabolites, contactlens wear or blepharitis. Photophobia, discharge, conjunctival injection, pain and reduced vision are common. You may see purulent material or cells in the bleb. Bleb-related endophthalmitis occurs when the infection spreads into the eye as evidenced by anterior chamber reaction, including hypopyon and vitritis. Bleb-related endophthalmitis requires emergent referral to a vitreoretinologist for culture of anterior chamber fluid and treatment with intracameral and intravitreal antibiotics.

► Shallow anterior chamber. This occurs frequently post-op and resolves without intervention. A flat anterior chamber with corneo-lenticular touch, however, is an indication for immediate referral to the surgeon for anterior chamber reformation. If contact between the cornea and lens occurs for a prolonged period, the cornea will decompensate, and the patient will lose visual acuity from corneal edema. In this case, a corneal transplant would become necessary to restore vision.

► Choroidal or retinal detachment. Because choroidal and retinal detachments can occur with a trabeculectomy, it's imperative you perform a posterior segment evaluation. In the case of choroidal detachments, the suprachoroidal fluid is gradually reabsorbed, so no treatment is necessary unless the choroidal detachments become so large that they touch. In the case of ‘kissing’ choroidals, scar tissue can form between the retinal surfaces. If the patient presents with this anomaly, refer him back to the surgeon for drainage of these fluid pockets. If the patient experienced sudden, severe pain and choroidal detachment after trabeculectomy, however, he may have a suprachoroidal hemorrhage that may require surgical drainage.

► Failing bleb. Ideally, the conjunctiva in the area of the bleb should be mildly elevated with diffuse or localized injection (see figure 1). Conjunctival injection isn't uncommon in the early post-op period, but it should quiet with the usual healing process and use of topical steroid drops. If the patient presents with conjunctival telangiectasia, carefully monitor him for increases in IOP at subsequent weekly visits, as this can be a sign of a failing bleb.

Attempt the Traverso maneuver (focal ocular massage) to test the function of the bleb. This requires you to instill a drop of topical anesthetic and apply a moistened sterile cotton swab to the conjunctiva adjacent to the edge of the scleral flap to allow aqueous outflow. If the trabeculectomy is functioning properly, aqueous fluid should gush into the bleb, creating a sudden elevation and expansion of the bleb. As a result, the patient's IOP should significantly decrease. If the post-massage pressure is still too high, however, consider scleral-flap suture removal or laser suture lysis to lower IOP. If the post-massage IOP remains elevated and the bleb remains low to flat, refer the patient for adjunctive subconjunctival injections of 5-fluorouracil (5-FU). Five-fluorouracil is an anti-cancer medication, diluted to a very low concentration to reduce scartissue formation.

► Encapsulated bleb or Tenon cyst. IOP increase associated with a focally elevated bleb and conjunctival telangiectasia is related to an encapsulated bleb or Tenon cyst. (see figure 2.) An encapsulated bleb requires the patient to perform ocular massage b.i.d. to q.i.d., placing pressure against the globe through the lids 180° from the bleb in an effort to disrupt the cyst wall several times daily in addition to aqueous suppressants as necessary. If the ocular massage isn't successful, the patient may require bleb needling or bleb revision surgery to remove scar tissue.

► Bleb dysesthesia or a symptomatic bleb. This can be problematic for some patients if the bleb is sufficiently elevated to cause surface disruption, such as dellen formation or irregular astigmatism from extension onto the cornea. If your patient presents with this finding, refer him for a bleb revision.

► Cataract. If the patient has a pre-existing cataract and glaucoma, consider referring him for a combined surgery, in which the surgeon performs cataract extraction with lens implantation and a filtering procedure, such as a trabeculectomy, in the same operation. Cataract is a common late after-effect of trabeculectomy surgery, however. If the patient develops cataract-induced blurred vision or glare, refer him back to the surgeon for cataract extraction. Some patients may require additional subconjunctival injections of 5-FU after cataract surgery, since the inflammation from cataract surgery can lead to bleb failure in some patients.

Co-management of glaucoma surgery can be a rewarding part of your optometric practice. As in any co-management relationship, it's essential to establish ground rules with your co-managing surgeon. This includes discussing when referral should occur for additional intervention and which key clinical signs and symptoms are important to communicate between providers. OM

Dr. Yang-Williams is a member of the Optometric Glaucoma Society and is in private group optometric practice in Seattle, Washington. E-mail her at kyangwilliams@q.com.