Improved Recovery, Reduced Risks

Regardless of the surgical operation, preoperative protocols have an essential role in helping us prevent infection, reduce pain and bleeding, and lower the risk of inflammation. Sometimes the steps are developed in the course of the procedure’s investigational process, other times we learn as we go and publish our results – and, often, we do both. For nearly every surgery, we continually adjust protocols based on new data or new drugs, working to incrementally improve our outcomes. Over time, the well-honed, evidence-based protocols become more effective and reliable. One example is the protocol for glaucoma procedures that involve a filtering bleb. Bleb procedures include traditional trabeculectomy and tube shunt surgeries, both of which are ab externo procedures that permit the aqueous to drain from the anterior chamber to the subconjunctival space. Another newer bleb procedure is the XEN Gel Stent (Allergan), a MIGS device that also creates drainage to the subconjunctival space with a stent implanted through an ab interno approach. XEN has a similar pressure-lowering effect with fewer risks than trabeculectomy and tube shunt (1), which can cause loss of best-corrected visual acuity, hypotony, choroidal effusion, cataract, and flattening of the anterior chamber (2-5).

I choose traditional filtering surgery for patients with open-angle glaucoma who are looking for a very low single-digit target pressure. XEN is used with mild to severe glaucoma patients who are uncontrolled or noncompliant with medications and/or are progressing but ideally need pressures in the low teens – with or without combined cataract surgery. Though different, all three procedures share preoperative considerations and protocols related to the filtering bleb.

The “basic” protocol

Although the goal of a preoperative protocol is to standardize the steps before surgery, it does not exist in a vacuum. Patients with glaucoma can have other ocular diseases, systemic comorbidities and medications that may affect surgery. Any preoperative approach must be customized to fit the individual’s needs and limitations. That customization does, however, begin with the same basic foundation. Our standard protocol before bleb surgery is topical steroid drops (typically dexamethasone 0.1 percent or prednisolone acetate 1 percent) four times per day for seven days (6). If the eye is infected or inflamed, we start topical steroids two to four weeks prior to surgery and watch for a potential steroid IOP response. To reduce this risk, when using steroids for more than two weeks, I advise using loteprednol 0.5 percent four times a day. We readily withhold offending topical glaucoma medications (ideally for one month prior to surgery), if we feel they are causing conjunctival infection or inflammation. To replace these medications, or if the IOP is uncontrolled, we add oral carbonic anhydrase inhibitors as needed. Changing to preservative-free glaucoma drops is another option, if preservative is thought to be the culprit. Topical antibiotics are only used two days before surgery. If a patient is taking anti-coagulants or anti-platelet medications or supplements, we discontinue these preoperatively to help reduce the risk of intraoperative bleeding (if cleared to do so by the patient’s internist) – the duration depends on the medication’s half-life.

Resolving ocular surface pathology

Ocular surface disease and blepharitis can also contribute to postoperative inflammation and scarring. When a patient has a healthy ocular surface and lid margins, we can schedule surgery and proceed with standard preoperative medications. However, if any problems are present on the ocular surface or lid margins, we need to resolve them before scheduling surgery and initiating standard steroids. Patients with dry eye should use non-preserved tears or gel lubricants, oral Omega 3 supplements and, if needed, cyclosporin A.

If blepharitis is present, I have patients perform lid hygiene, take oral doxycycline, and use erythromycin ointment and topical steroids. For patients with a combination of any of these ocular surface and lid margin problems, treatment is customized to ensure that all issues are addressedbefore surgery. These therapies may need to be continued postoperatively and indefinitely to preserve conjunctival health for good bleb function.

All of these therapies are initiated at least one month before surgery. If the ocular surface is clear and quiet at this point, we can proceed with the standard week of steroid drops before surgery. If the patient still has red eye or other symptoms, my advice is to delay surgery and adjust treatment before continuing therapy. In treating ocular surface disease and/or blepharitis before glaucoma surgery, we sometimes need to tolerate moderate elevation of IOP for a few weeks. Certain therapy choices may also require additional IOP monitoring. For instance, if we add steroids for more than two weeks, I would check the IOP again.

Completing the protocol in the surgery center

Once ocular surface and lid margin problems are resolved, the patient has come off any medications as instructed, and the standard course of preoperative medications is complete, the remaining steps of the preoperative protocol can take place in the surgery center. Here, patients are prepared with topical steroids, NSAIDs and antibiotics. We use topical tetracaine 0.5 percent for anesthesia and instill a drop of phenylephrine 2.5 percent on the superior conjunctiva for vasoconstriction to minimize bleeding risk.

For my trabeculectomies and XEN procedures, I administer 0.1 cc of mitomycin-C (0.4mg/cc) subconjunctivally posterior to the limbus (>6 mm from limbus) for most eyes to provide wound-healing modulation. I inject this intra-Tenons to prevent it from dispersing everywhere, and keep it posterior, avoiding limbal pooling. I do not typically use mitomycin-C for the Baerveldt Glaucoma Implant (Advanced Medical Optics), but do use it occasionally when implanting the Ahmed Glaucoma Valve (New World Medical).

The outcome we anticipated

Preoperative protocols are designed to optimize outcomes and improve predictability. When we adhere to them routinely, we know what results we can comfortably expect from surgery. For filtering bleb surgeries, that can mean less fibrosis, bleeding and inflammation. Particularly for traditional surgeries like trabeculectomy and tube shunt, preoperative protocols go a long way to reducing surgeon stress and building confidence in the procedures.