Filtration Surgery: Will the Art Be Lost?

Educational Objectives

The goal of this program is to improve filtration surgery techniques for patients with glaucoma. After hearing and assimilating this program, the clinician will be better able to:

1. Cite factors contributing to the decline in filtration surgery for patients with glaucoma.
2. Select the most appropriate filtration surgery for individual patients with glaucoma.

Summary

Trends in glaucoma surgery: decrease in filtration surgery started 15 to 20 yr ago, in part because of the procedure itself and because younger generations of glaucoma surgeons are seeking quicker and more predictable methods of controlling intraocular pressure (IOP); trabeculectomy and aqueous shunts to the subconjunctival space (ExPRESS) are difficult to perform and tedious, perioperative care can be arduous, and outcomes can be unpredictable; however, filtering surgery is the best way to control IOP, especially for people with severe glaucoma; Yang et al (2021) analyzed data from the IRIS registry between 2013 and 2018 and found a large increase in microinvasive glaucoma surgery (MIGS) procedures performed, whereas trabeculectomy decreased by 50%; the number of people with glaucoma exponentially increased over that timeframe; review of Medicare data (Boland et al [2021]) found that 75% of glaucoma procedures performed in 2017 were MIGS, and 25% of the procedures were filtering surgeries (evenly divided between trabeculectomy and glaucoma-draining devices)

Trabeculectomy: considered the gold standard; provides long-term control of IOP, often without medical therapy; use peaked in 1980s and 1990s; Migdal et al (1994) found that patients who were randomized to receive trabeculectomy had better stabilization of disease compared with those who received medical therapy or laser therapy, and performing the procedure earlier was associated with better outcomes; in the CIGTS trial (Musch et al [2009]), many patients with newly diagnosed glaucoma who were randomized to receive surgical or medical therapy had stabilization or cure of glaucoma over 10 yr of follow-up; increasing doses of mitomycin C in the late 1990s resulted in bleb thinning and breakdown and an increase in infections, encouraging experts to seek a more reliable and predictable procedure; ≈10 yr ago, reimbursement for trabeculectomy decreased by ≈20%; 50 to 70 large centers throughout the United States perform 80% to 90% of filtration surgeries, forcing most patients to travel long distances for surgery, further decreasing the number of procedures performed, and increasing the difficulty in training new glaucoma specialists who have less experience with procedures and follow-up and thus feel less comfortable performing the procedure; number of trabeculectomies done by a glaucoma fellow in training has decreased 33%, compared with 8 yr ago; additionally, these glaucoma specialists do not feel comfortable or have back-up if they do not perform the procedure at a large center

Trabeculectomy vs MIGS: Fili et al (2022) found that a poly(styrene-block-isobutylene-block-styrene) subconjunctival draining MIGS device (PreserFlo Microshunt) was inferior to trabeculectomy for lowering of IOP; study of a cross-linked porcine gelatin stent (Xen gel stent) showed similar results; however, generations comfortable performing trabeculectomy are leaving the ophthalmology practice

Surgeon skill: data from the CIGTS trial (Musch et al [2009]) found a large variability in surgeon procedures among those who perform trabeculectomy

Clinical Pearls for Filtering Surgery

Procedure selection: depends on the patient, diagnosis, age, and prior surgeries; drainage devices are used for most cases of secondary glaucoma; trabeculectomy or aqueous shunts to the subconjunctival space are typically used for primary glaucoma; trabeculectomy filters at the limbus; Xen and PreserFlo filter 3 to 5 mm off the limbus; glaucoma drainage devices filter in the orbit; conjunctival health is an important consideration when selecting a procedure; young patients need larger plates than older patients (who do not produce enough aqueous to support the valve)

Achievement of goal IOP: IOP lowering can be gradual; slowly cut sutures (over ≤4 wk) postoperatively; cut the temporal sutures first because temporal blebs are more comfortable than nasal blebs; avoid overshooting IOP lowering; closure of the conjunctiva is critical; for fornix-based flaps, leave a small portion of conjunctiva attached to the cornea to allow it to find the cut conjunctiva to heal back toward; promptly treat leaks; place a 15-mm contact lens over the limbus to enable prompt healing; apply a bandage contact lens to aggressively treat early hypotony (overfiltering bleb), and reduce aqueous suppressants in the contralateral eye; inadequate aqueous production, common among Black patients, can occur due to effects of preoperative aqueous suppressants or inflammation related to surgery, and may contribute to relatively poor filtration

Cross-linked porcine gelatin stent: ensure the needle tract is sufficiently long (so the stent can swell and fill the tract) to avoid leak during the first 48 to 72 hr postsurgery; intraoperatively apply an ophthalmic viscoelastic agent to plug the leak; compared with trabeculectomy or aqueous shunts to the subconjunctival space, dose of mitomycin C is higher, and topical steroids are used for a longer duration (3-4 mo) after surgery with a slow taper, due to increased incidence of late scarring with filtering surgery compared with other procedures; early failure often occurs when the distal end of the filtering device is trapped within Tenon space (most likely cause if the device appears curved); use a blunt instrument to milk the conjunctiva over the distal end of the tube

Trabeculectomy and aqueous shunts to the subconjunctival space: only titratable filtration procedures available, ie, allows for a gradual decrease in IOP for patients with severely elevated IOP to prevent hypotony; underfiltration is typically a more successful strategy than overfiltration; with trabeculectomy, the size of the sclerostomy can be adjusted during the procedure (eg, make a smaller sclerostomy if the flap is thin); avoid creating a bridge (occurs if the sclera collapses under the trabeculectomy; can be corrected by loosening the sutures or creating side sutures); selection of plate size depends on patient age and goals of the procedure; suture the plate to avoid sagging over the lateral rectus muscle and anterior movement; use the superior rectus tendon to place the most medial suture (thickest part of the sclera); place at least one suture in the scleral patch graft to avoid drifting over the cornea (glue is often insufficient)

Readings

Fili S, Kontopoulou K, Vastardis I, Perdikakis G, Kohlhaas M. PreserFlo™ MicroShunt versus trabeculectomy in patients with moderate to advanced open-angle glaucoma: 12-month follow-up of a single-center prospective study. Cureus. 2022;14(8):e28288. doi:10.7759/cureus.28288; Lim R. The surgical management of glaucoma: A review. Clin Exp Ophthalmol. 2022;50(2):213-231. doi:10.1111/ceo.14028; Migdal C, Gregory W, Hitchings R. Long-term functional outcome after early surgery compared with laser and medicine in open-angle glaucoma. Ophthalmology. 1994;101(10):1651-6; discussion 1657. doi:10.1016/s0161-6420(94)31120-1; Musch DC, Gillespie BW, Lichter PR, et al. Visual field progression in the Collaborative Initial Glaucoma Treatment Study the impact of treatment and other baseline factors. Ophthalmology. 2009;116(2):200-7. doi:10.1016/j.ophtha.2008.08.051; Patel S, Pasquale LR. Glaucoma drainage devices: a review of the past, present, and future. Semin Ophthalmol. 2010;25(5-6):265-70. doi:10.3109/08820538.2010.518840; Wu AM, Zhao Y, Friedman DS, et al. Trends in glaucoma fellowship surgical experience. Invest Ophthalmol Vis Sci. 2022;63(7):3721–A0406; Yang SA, Mitchell W, Hall N, et al. Trends and usage patterns of minimally invasive glaucoma surgery in the United States: IRIS® registry analysis 2013-2018. Ophthalmol Glaucoma. 2021;4(6):558-568. doi:10.1016/j.ogla.2021.03.012; Yang X, Zhao Y, Zhong Y, et al. The efficacy of XEN gel stent implantation in glaucoma: a systematic review and meta-analysis. BMC Ophthalmol. 2022;22(1):305. doi:10.1186/s12886-022-02502-y.

Disclosures

For this program, the following relevant financial relationships were disclosed and mitigated to ensure that no commercial bias has been inserted into this content: Dr. Simmons has been on the speaker's bureau for Abbvie/Allergan and Bausch + Lomb. Members of the faculty reported nothing relevant to disclose.

Acknowledgements

Dr. Simmons was recorded at 22nd Annual Downeast Ophthalmology Symposium, held September 29 to October 1, 2023, in Bar Harbor, ME, and presented by Maine Society of Eye Physicians and Surgeons. For information on future CME activities from this presenter, please visit https://www.maineeyemds.com. Audio Digest thanks the speakers and presenters for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0.75 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0.75 CE contact hours.

Lecture ID:

OP620201

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.

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