Over the past decade, we in the glaucoma world have witnessed the advent of many new laser and surgical approaches to lower IOP. These new treatment strategies are welcome, but the necessary clinical trials comparing the different modalities are lacking. In some cases, well-designed clinical trials are nonexistent. Therefore, we need to rely on the experience of early adapters for information on efficacy and safety as well as pearls to optimize outcomes. In this issue, we have asked these early adapters to write about their experiences.
The trabecular meshwork represents an important site of resistance to outflow of aqueous humor and, therefore, an important determinant of IOP. Our writers discuss the novel surgical approaches designed to bypass or eliminate this site of resistance, including Trabectome, iStent, Hydrus, new gonioscopy-assisted transluminal trabeculotomy and ab interno canaloplasty procedures and trabeculectomy with the Kahook dual blade.
Several new devices aim to lower IOP by shunting aqueous from the anterior chamber to the suprachoroidal space; CyPass is the first to achieve FDA approval. One article summarizes the recently published evidence in this arena.
We now have ways to reduce aqueous flow using cyclodestructive laser technology. The MicroPulse diode laser utilizes short pulses of energy rather than a continuous wave, as with the traditional diode laser. Brian Francis, MD reviews the evidence and offers pearls on the use of trans-scleral and endoscopic diode laser cyclophotocoagulation.
Why are clinical trials so critical in assessing the efficacy of glaucoma surgery? Clinicians’ experiences with many of these new procedures are likely favorable when they evaluate their own data. That is because many of these procedures are intended to be combined with phacoemulsification, an operation that by itself is substantially effective in lowering IOP. When rigorously controlled clinical trials are performed, some of these new operations have only modest IOP-lowering efficacy compared to phacoemulsification alone. The surgeon must always follow the basic principle of weighing the potential risks of an intervention against its known benefits. To this end, post-marketing surveillance will be important.
A final point concerns the role that disease severity plays in the selection of a therapeutic strategy. Glaucoma is an optic neuropathy, and disease severity is defined by the extent of vision loss and optic nerve damage. The level of IOP, however, is an indicator of the severity of the abnormality of the outflow system. While the word “severity” comes up twice, it describes two different things that may or may not be synchronized in the same eye of a given patient. Both factors must be considered in determining the best approach to sufficiently slow the disease and prevent further vision loss.
Ophthalmologists have much to be excited about; we are in the midst of a revolution with many new glaucoma surgical approaches available and more on the horizon. The challenge will be to determine which procedures to adopt into practice and for which patients. The articles in this issue will begin to pave the way to the best answers to those questions. OM