Risk Management

Risk of Using — and Not Using — Antimetabolites in Glaucoma Surgery

By B. Thomas Hutchinson, MD, and E. Randy Craven, MD

Argus, September, 1996

Although the general medical and disease-specific risk factors for glaucoma surgery are well known and discussed as part of the informed consent process, many ophthalmologists do not commonly address the use of operative and postoperative antimetabolites. Their use can mean the difference between success and failure in glaucoma filtration surgery. The surgeon who fails to discuss with the patient the rationale behind the decision faces potential liability if the patient is unhappy with the outcome.

Even when used appropriately, these agents may cause serious postoperative complications and introduce significant risks for the future. Although no definitive criteria have been established for their use in glaucoma filtration surgery, a consensus is evolving as to when they are most valuable.

Mitomycin-C and 5-Fluorouracil, the most commonly used antimetabolites, may significantly benefit eyes expected to have an excessive fibroproliferative response. Examples include previously operated eyes, failure of previous filters in the same or other eye, coexisting uveitis or rubeosis, combined glaucoma and cataract surgery, and risk factors related to the patient’s age and race.

Since most glaucomacologists do not use these agents routinely in every case, it is equally important to tell the patient why they might not be used, for example, in eyes with no unusual risk factors for failure. The ophthalmologist might elect not to use Mitomycin-C in patients who are at added risk for antimetabolites such as the moderate to highly myopic eye, patients with hypotony after previous surgery (with or without antimetabolites), and patients with potentially complicating corneal, retinal or wound healing problems. In today’s medicolegal practice arena, it is perhaps as important to discuss use and nonuse of these modalities as it is to discuss the rationale for and against the surgery itself.

In addition to the usual complications of glaucoma surgery, it is not uncommon for the “antimetabolite bleb,” especially with Mitomycin-C, to provide overfiltration, initially associated with hypotony and often retinal edema. The use of Mytomycin-C may place the eye at additional future risk of late bleb leak and necrosis of avascular tissue as well as a higher incidence of late bleb infection and endophthalmitis. The hypotony and retinal edema now recognized as a more frequent occurrence with antimetabolites do not commonly respond to medical or surgical attempts at correction. Potential complications of using antimetabolites should be discussed with the patient, along with the risk of failure for glaucoma control without using these new modalities.

It is crucial that the patient understand not only the spectrum of glaucoma as a potentially blinding disease but also the likelihood of success with all modalities of treatment consistent with the patient’s particular disease. In making a decision about surgery, there must be ample opportunity to educate and include the patient in the decision-making process about the concept of surgery as well as adjunctive treatments that may be appropriate for a particular patient. Educating the patient about your rationale for deciding whether to use these new and often valuable antimetabolite medications will clearly identify you as the patient’s advocate and reduce the likelihood that you will become adversaries in the future.

OMIC provides model patient information sheets regarding the use of Mitomycin-C and 5-Fluorouracil during glaucoma surgery, which you can give to patients prior to surgery. Fax your request for these documents to the OMIC Risk Management Department, 415 771-1095.