Trabeculectomy remains the gold standard procedure for patients with advanced or rapidly progressing glaucoma who need very low intraocular pressures. When successful, the procedure offers long-term IOP control without an implanted device and the opportunity to titrate filtration to achieve a desired goal. For many with severe disease, a trabeculectomy is the best and only reasonable option. However, with the decreasing number of trabeculectomies performed in training programs, there’s a concern that this surgery could fall by the wayside if the next generation of glaucoma specialists is not adequately trained in the performance and perioperative management associated with this procedure.
There are a number of reasons for this—some within our control and others outside of it—but one thing is certain: The population is aging, and the prevalence of glaucoma is increasing. As patients live longer with glaucoma, there will be many more who need trabeculectomy to prevent blindness in their lifetimes.
Tortoises and Hares
The majority of patients who are diagnosed as having glaucoma and treated with IOP lowering therapy have slowly progressive disease. Many such patients tend to experience very little visual field loss over their lifetime, and their disease can usually be managed using topical medications, lasers or minimally invasive glaucoma surgery. With few visual symptoms, especially in early stages, many such individuals are completely unaware that they have glaucoma. Major trials such as the United Kingdom Glaucoma Treatment Study and the Early Manifest Glaucoma Trial have shown that approximately 66 percent and 33 percent of patients receiving placebo or no therapy do not show progression of glaucomatous disease respectively.1-2
Only a small subset of patients are fast or catastrophic progressors as demonstrated by a Canadian analysis of 2,324 patients in clinical care, where 4.3 percent displayed fast progression (defined as mean deviation <-1 to -2 dB/year) and 1.5 percent showed “catastrophic” progression (MD <-2 dB/year).3 Though the proportion of fast and catastrophic progressors is small, the rate increases with advancing age.
A Vanishing Act
As the population ages, we can expect an increase in the number of glaucoma patients in their 80s and 90s along with a corresponding increase in the absolute number of cases with advanced glaucoma.4 Some of these older patients will require more aggressive pressure lowering, with IOP goals in the single digits—a feat unlikely to be accomplished without trabeculectomy, which remains the only glaucoma procedure associated with a high likelihood of achieving IOPs in this low of a range.
Despite the sizable projected public health need for trabeculectomy in the next couple of decades, there’s a very real risk that trabeculectomy could disappear from our armamentarium. So, why aren’t doctors offering trabeculectomy to patients with severe disease? There may be a number of reasons. Here are a few:
- They didn’t adequately learn trabeculectomy in their training so they either don’t feel comfortable performing the procedure or get poor results.
- They choose not to perform trabeculectomy for other reasons such as perioperative effort or insufficient reimbursement.
- They’re not aware of the data showing the benefits of trabeculectomy in glaucoma patients with potentially blinding disease, as such data isn’t commonly presented at contemporary meetings. This reason is particularly problematic because it may preclude patients being offered the opportunity to see other practitioners who are adequately trained and available to provide vision saving trabeculectomy. As one of my mentors once said: You don’t know what you don’t know.
Trabeculectomy is taught less than in the past because there are so many newer surgeries and devices to choose from, such as tube shunts and MIGS. In U.S. glaucoma fellowship training, the median number of trabeculectomy or Ex-Press shunt procedures performed with fellows as the primary or assisting surgeon decreased from 49 to 32 over a five-year period (2014 to 2019) whereas over that same period, the number of aqueous shunt procedures remained roughly the same at 55 and 57 procedures, respectively. The median number of trabeculectomy and aqueous-shunt revision surgeries remained reasonably stable as well (ranges for both: 9 to 14), but the number of primary surgeon ab interno angle procedures increased from zero to 12.5
Many of the surgeons experienced in the art of trabeculectomy—particularly the early postoperative manipulation required for a successful procedure—are retiring or nearing retirement. As they leave the field it can become difficult to find a doctor in many parts of the United States who can perform or teach this procedure with high success and a low risk of complications. If trabeculectomy needs to be repeated, then there are additional risks such as scarring and bleb failure as well as lower success rates, so the best shot you get with trabeculectomy is usually as the first conjunctival incisional procedure.
If young surgeons don’t receive sufficient training, they won’t get good results. This will undoubtedly make them hesitant to perform trabeculectomy because they lack confidence in the procedure. This in turn causes a vicious cycle where fewer trabeculectomies leads to less trabeculectomy training, which leads to fewer surgeons performing trabeculectomy.
Even some glaucoma specialists are shying away from trabeculectomy—sometimes perhaps for financial reasons. From a business standpoint, a MIGS practice may be more attractive to some due to MIGS’ relative simplicity, low complication rates and higher reimbursement per time spent. Trabeculectomy has a steep learning curve and, in addition to intraoperative complexity, good results generally require multiple postoperative visits in the weeks following surgery, with timely interventions to safely titrate IOP to desired goals. Such interventions include digital massage, lysing or releasing scleral flap sutures, as well as administration of subconjunctival antifibrotic agents such as 5-fluorouracil. Many clinics either can’t provide or don’t want to provide such postoperative care.
Based upon Medicare data, the number of trabeculectomies is going down at a time when, based upon our population demographics, the number of patients needing trabeculectomy is likely going up. These dynamics have the potential to lead to a public health crisis. This is a tough area to study, but my clinical impression is that there are more glaucoma patients going blind today because they didn’t get a timely trabeculectomy relative to a decade ago, often because their doctor didn’t offer this as an option or, alternatively, refer them to another physician who was adequately trained and willing to perform the procedure.
Who Needs a Trab?
Glaucoma surgery can be divided into broad categories: procedures that increase outflow by enhancing the eye’s natural drainage pathways (e.g., implantable MIGS devices); by creating a new drainage system (e.g., filtration and shunt surgeries); or procedures that decrease inflow, such as cyclophotocoagulation.
When choosing a glaucoma procedure, consider the following factors:
- glaucoma risk (age, severity, progression);
- lens status;
- IOP goals for the procedure;
- medication tolerance/acceptance; and
- preserving future options.
Patients with mild to moderate glaucoma who are taking IOP-lowering medications are candidates for implantable MIGS devices combined with cataract surgery, an approach that has been well-studied in several major clinical trials as a way to decrease dependence on such medications. Choice of MIGS depends on surgeon comfort or preference as well as individual ocular anatomy and pressure-lowering needs.
Most people who get MIGS today are unlikely to be destined to noticeably lose sight in their lifetimes. Most won’t go on to have vision loss resulting in an inability to read, drive or watch TV. In contrast, patients who are candidates for trabeculectomy generally have more advanced and/or rapidly progressive disease and are thus likely to have these hurdles in their future. So, it’s possible that because of the increasing popularity of and preference for MIGS, and the corresponding decrease in the number of trabeculectomies performed, that we may see more glaucoma-related blindness in the years to come, despite having these newer surgeries. It would be most unfortunate if the revolution in novel glaucoma surgical procedures, by leading doctors away from trabeculectomy, results in greater glaucoma-related blindness in fee-for-service populations such as in the United States.
Trabs’ Track Record
We can’t let trabeculectomy fall by the wayside. Trabeculectomy has a long history of success, yielding sustained low pressures and slowing of disease progression. Postoperative titration is possible, and it’s also been shown that the procedure can improve visual function.6
A study of normal-tension glaucoma patients reported a mean IOP decrease from 15.7 to 10.3 mmHg and a decreased VF progression rate from 0.70 to 0.25 dB/year five years after trabeculectomy.7 Another study reported pre-trabeculectomy VF progression decreased from 1.1 dB/year (mean IOP 13.5 mmHg) to 0.25 dB/year (8.5 mmHg) six years after surgery.8
In the Tube Versus Trabeculectomy study, similar mean pressures were achieved but fewer medications were needed by the group that received trabeculectomy for the first few years after surgery but not at five years (14.4 ±6.9 mmHg in the tube group vs. 12.6 ±5.9 mmHg in the trabeculectomy group; p=0.12; 1.4 ±1.3 medications in the tube group vs. 1.2 ±1.5 medications in the trabeculectomy group; p=0.23).9 While the mean IOPs were similar, the proportion of eyes with very low pressures was greater in the trabeculectomy group. Patients with advanced disease may sometimes require single digit IOPs to adequately slow disease progression.
When performed with 5-fluorouracil or mitomycin-C, trabeculectomy has been found to produce safe and effective pressure reduction. In a prospective, randomized, multicenter trial, 113 patients were randomized to receive 5-FU (50 mg/ml for five minutes) or MMC (0.4 mg/ml for two minutes). A total of 108 patients were analyzed (n=54 for each group). In the MMC group, 89 percent reached the predefined target IOP <18 mmHg after surgery vs. 83 in the 5-FU group; 70 vs. 73 percent reached IOP <15 mmHg; and 53 vs. 38 percent reached IOP <12 mmHg, respectively (no significant difference).10
Importantly, a paper by Joseph Caprioli, MD, and colleagues demonstrated that trabeculectomy can slow the rate of perimetric decay and may improve long-term visual function in glaucoma.6 In the retrospective, longitudinal study, 74 eyes of 64 OAG patients underwent trabeculectomy with MMC. A control group of 71 unoperated eyes of 65 patients with similar baseline characteristics was included. The authors reported that the mean rate of change for all VF locations slowed after surgery, from -2.5 ±9.3 percent/year before surgery to -0.10 ±13.1 percent/year after surgery (p<0.001). In the trabeculectomy group, they observed that 70 percent of locations decayed before surgery versus 56 percent of locations after surgery; they also observed improvement in 30 percent of locations before surgery and in 44 percent after surgery (p<0.0001). IOP reduction was associated with the excess number of VF locations showing long-term improvement (p=0.009). In the trabeculectomy group, 57 percent of eyes showed improvement in 10 or more VF locations postoperatively.
What Can We Do?
More people will need trabeculectomy in the next 20 to 30 years, but with fewer doctors well-versed in the procedure, lack of training, declining reimbursement and insufficient knowledge about what trabeculectomy can do, we may find ourselves with a public health crisis on our hands.11
Here are some steps to ensure we’re ready to meet the needs of our patients:
1. Ensure that the training programs and physicians who have the ability to teach trabeculectomy continue to do so. Teaching the art and science of trabeculectomy will be vital for the survival of the procedure. One of the most valuable training techniques for trabeculectomy is direct mentoring with an experienced glaucoma surgeon, in addition to postoperatively following a number of cases.
2. Physicians who perform trabeculectomy should get adequately reimbursed for their effort. This isn’t directly in our hands, but advocacy measures may help raise awareness. Currently, some doctors may have a disincentive to do trabeculectomy because reimbursement is too low for the complexity and amount of time devoted to the procedure and postoperative care. Surgeons’ payment should be similar to what they’re doing in other areas of practice—if a trabeculectomy takes twice as much effort as another procedure, pay twice as much, and that includes postoperative care.
3. We need more traditional glaucoma doctors to ensure that we can meet the needs of people with glaucoma. Some and perhaps many fellowship-trained glaucoma specialists are developing cataract/MIGS practices and don’t want to bother taking care of patients with severe or high-risk glaucoma.
If we create a culture that recognizes trabeculectomy’s place in glaucoma management, we can better equip ourselves and the next generation of surgeons to learn and practice the art and science of trabeculectomy.
Dr. Singh is a professor of ophthalmology and chief of the Glaucoma Division at Stanford University School of Medicine. He is a consultant to Alcon, Allergan, Santen, Sight Sciences, Glaukos and Ivantis. Dr. Netland is Vernah Scott Moyston Professor and Chair at the University of Virginia in Charlottesville.
1. Garway-Heath DF, Crabb DP, Bunce C, et al. Latanoprost for open-angle glaucoma (UKGTS): A randomised, multicentre, placebo-controlled trial. Lancet 2015;385:9975:1295-1304.
2. Heijl A, Leske MC, Bengtsson B, Hyman L, Bengtsson B, Hussein M et al. Reduction of intraocular pressure and glaucoma progression: Results from the Early Manifest Glaucoma Trial. Arch Ophthalmol 2002;120:10: 1268-1279.
3. Balwantray CC, Malik R, Shuba LM, et al. Rates of glaucomatous visual field change in a large clinical population. Invest Ophthalmol Vis Sci 2014;55:4135-4143.
4. NORC at Chicago. Prevent Blindness America Future of Vision Report 2014. https://preventblindness.org/wp-content/uploads/2020/04/Future_of_Vision_final_0.pdf. Accessed February 1, 2023.
5. AUPO-FCC website. https://aupofcc.org/system/files/resources/2019-12/Procedures%20reported%20by%20Glaucoma%20Fellows%20in%20Exit%20Surveys%202014-19.pdf. Accessed February 6, 2023.
6. Caprioli J, de Leon JM, Azarbod P, et al. Trabeculectomy can improve long-term visual function in glaucoma. Ophthalmol 2016;123:117-128.
7. Mataki N, Murata H, Sawada A, et al. Visual field progression rate in normal tension glaucoma before and after trabeculectomy: A subfield-based analysis. Asia Pac J Ophtahlmol (Phila). 2014;3:263-266.
8. Iverson SM, Schulyz SK, Shi W, et al. Effectivness of single-digit IOP targets on decreasing global and localized visual field progression after filtration surgery in eyes with progressive normal tension glaucoma. J Glaucoma 2016;25:408-414.
9. Gedde SJ, Schiffman JC, Feuer WJ, et al. Treatment outcomes in the Tube Versus Trabeculectomy (TVT) study after five years of follow-up. Am J Ophthalmol 2012;153:5:789-803.
10. Singh K, Mehta K, Shaikh NA, et al. Trabeculectomy with intraoperative mitomycin C versus 5-fluorouracil: Prospective randomized clinical trial. Ophthalmology 2000;107:2305-2309.
11. Singh K, Sherwood MB, Pasquale LR. Trabeculectomy must survive! Ophthalmol Glaucoma 2021;4:1:1-2.