Glaucoma Surgery: Where We Started and Where We Are Going
(Note that this was commentary originally authored in 2011-2012)
The world of glaucoma is vastly different now than when I first trained as a fellow from 1983 to 1984. Although the indications to perform glaucoma surgery have remained similar, the procedures available have advanced considerably. In fact, the scenario of the surgical arena in 1983 is no longer recognizable, with amazing changes occurring since then.
Let me paint the surgical picture during my fellowship with George Spaeth and Rick Wilson at Wills Eye Insitute in Philadelphia, Pennsylvania. The standard of care included large wound extracapsular cataract surgery combined with trabeculectomy (no antimetabolites), limbal-based trabeculectomies, cyclodialysis cleft formation, and bedside cryotherapy in aphakes. Patients received a retrobulbar and facial nerve block, and everyone was admitted as an inpatient. All the eyelashes were clipped and the head was draped with towels and towel clips. As a fellow, it was not uncommon to round twice a day on 20 inpatients at Wills Eye Hospital, as patients typically remained in the hospital for 4 to 5 days.
Phacoemulsification was coming of age and early on, large poly-methylmethacrylate (PMMA) lenses placed in-the-bag were the first to become available. Can opener capsulorrhexis with a 25-gauge needle was routine, retained cortical remnants were no surprise, and foldable lenses were not yet invented. The combined extracapsular cataract and glaucoma surgery, as I first learned it, took easily over an hour. When 10 cases were scheduled, we would start in the morning and operate till evening. Everyone was patched, and because all eyes were blocked, the “occasional” retrobulbar hemorrhage was not really uncommon. Because antimetabolites were not yet available, scarring was almost routine. Postoperative modification of large amounts of cylinder via suture manipulation was commonplace after combined surgery when at least 6 to 8 nylon sutures closed the superior wound. Needling the bleb was unheard of, and our only option then to increase flow was laser suture lysis or subsequent tube shunt surgery (first Schockett, then Molteno, and the other shunts followed).
Having watched all these changes evolve, the real advantage that has advanced the field of glaucoma surgery is surgeon control. We are no longer filleting the eye open to remove large phacomorphic lenses, thus the risk of expulsive hemorrhage is way down. I recall assisting George Spaeth in man-aging 2 expulsives on 1 day during combined procedures.
We now have releasable sutures that can meticulously control the amount of aqueous flow in the postoperative period. Using a combination of topical, intracameral, and subconjunctival/Tenon’s lidocaine, all glaucoma surgeries can be performed without either a peribulbar or retrobulbar block, allowing for immediate vision postoperatively. This is most helpful in monocular patients. Trabeculectomies or guarded filtration procedures can be done with either a fornix or the traditional limbal-based flaps. Antimetabolites like mitomycin C (MMC) placed with sponges or injected at the time of surgery improve the success. Failing trabeculectomies can be brought back to life with a combination of lidocaine and MMC injected at the time of needling. In addition, user-friendly viscoelastics can man-age the chamber depth at the slit lamp should too much aqueous escape early on. Stronger topical and intracameral nonpreserved steroids, such as Triesence (triamcinolone acetonide), are now available to eradicate postoperative inflammation. We now have choices regarding lens implants and can correct large amounts of pre-existing astigmatism with toric implants, either simultaneously with cataract and glaucoma surgery or following trabeculectomy. Tube shunt options are now plentiful, and adopting techniques that modify flow early on improve the quality of the patient’s vision by avoiding profound hypotony. Additionally, covering the tubes with either pericardium, sclera, amniotic membrane, or partial-thickness cornea gives the surgeon many options to better treat the individual. One advance has been the Ex-Press shunt. Unfortunately, it is still bleb-dependent, but the whole idea of standardizing glaucoma surgery so it is done efficiently with predicted flow, recognized outcomes, and fewer complications will form the new template for the future. If better control of aqueous inflow is desired, excellent visualization of the ciliary body with an endoscopic illuminator allows for limited ciliary body destruction, making cyclocryotherapy a thing of the past.
Where are we going from here? I do believe that despite the amazing advances noted above, glaucoma surgery is still in its infancy. Efforts are being made to change the morphology of the blebs by making them lower and more diffuse, with less of a tendency toward perforation or infection. A new product, Ologen (Aeon Astron, Leiden, The Netherlands), which is a collagen matrix and space maintainer, is one such idea to replace the use of MMC. I look forward to other products that will truly prevent scarring while allowing the ophthalmologist to manipulate trabeculectomy flap sutures if needed. In the future, closure with nylon sutures may be drastically reduced with affordable tissue glue products. Canaloplasty is still evolving, and I envision the surgical delivery of new drugs directly into Schlemm’s canal. This may drastically modify the trabecular outflow mechanism, allowing for meticulous intraocular pressure (IOP) control while forgoing the use of topical medications and eliminating the need for blebs entirely. In addi-tion, genetic manipulation, either intracamerally or via Schlemm’s canal, may consistently lower the IOP so the optic nerve can thrive. Exploring the suprachoroidal space with an implant that allows for controlled drainage of aqueous is likely to become available, perhaps with sensors attached that will be able to constantly monitor the IOP. These are just a few of the many advances I envision that will help make glaucoma surgery safer and predict-able so as to finally limit glaucomatous blindness that threatens so many throughout the world.