40 Incorporating Minimally Invasive Glaucoma Surgery Procedures Into One’s Practice Minimally invasive glaucoma surgery (MIGS) offers a new avenue for interventional treatment for glaucoma patients. Instead of waiting until patients have severe disease with advanced surgical requirements, MIGS procedures can be performed on their own or combined with cataract surgery to provide additional intraocular pressure (IOP) lowering or reduction in the number of topical hypotensive agents. Prior to beginning down the pathway of incorporating MIGS into your surgical repertoire, it is important to adequately prepare yourself and your practice. The decision of which MIGS device to proceed with is largely based on patient selection, disease type, and planned surgical procedures that will accompany the MIGS procedure. Furthermore, capital costs for relevant equipment may play a role in some device or procedure selection. Consideration of the type of glaucoma and the desired IOP target should also help to determine which device or modality to choose for a given patient. Although this book described numerous devices and procedures that fall under the rubric of “MIGS,” the discussion below focuses on the choice between the Trabectome and iStents. Trabectome™ (NeoMedix, Tustin, CA) is a single-use bipolar cautery device with irrigation and aspiration that enables the surgeon to perform ab interno trabeculotomy (Figs. 40.1 and 40.2). It is used for the management of open-angle glaucoma, but has also been used in the setting of angle-closure glaucoma after goniosynechiolysis and lens extraction. Given a moderate IOP reduction found with the Trabectome, the technique is used for mild-to-moderate glaucoma disease burden.1 The technique can be performed on its own or typically in combination with clear corneal phacoemulsification; studies indicate that the combination surgery results in improved IOP reduction as compared with phacoemulsification alone. The learning curve associated with the Trabectome primarily entails gaining familiarity with angle surgery itself. There is indeed a learning curve associated with correctly performing intraoperative gonioscopy. Appropriate patient selection for the first several cases will optimize surgeons’ ability to quickly familiarize themselves with the nuances of intraoperative angle visualization and manipulation. There are capital costs associated with setting up your practice to use the Trabectome. One must acquire the Trabectome system itself, along with an appropriate goniolens and individual procedure packs. The iStent® Trabecular Micro-Bypass (Glaukos, Laguna Hills, CA) is the world’s smallest implant approved for human use. It is a 1-mm titanium microstent that is implanted directly into Schlemm’s canal, thereby enabling aqueous humor to bypass the high-resistance juxtacanalicular trabecular meshwork (Figs. 40.3 and 40.4). The iStent is indicated for the treatment of primary open-angle glaucomas in combination with cataract extraction, and, as with other MIGS procedures, it is recommended for mild-to-moderate disease.2,3 iStent implantation has been used to augment cataract surgery in patients with angle-closure glaucoma, and some surgeons have performed iStent implantation as a solo procedure. Surgeons note a steep but relatively short learning curve with the iStent. In addition to familiarity with intraoperative gonioscopy, successful surgery involves fine movements and angulations of the fingers and wrists to achieve implantation and maintain adequate visualization (Figs. 40.5 and 40.6). Patient head positioning and microscope positioning are essential to obtain the proper viewing angle for iStent placement, and comfort with these skills is part of the steep learning curve associated with this device. Capital costs associated with the iStent are minimal. In addition to a microscope that is capable of tilting, the main capital investment required in iStent implantation is in a high-quality intraoperative gonioscopy lens. Direct gonioprisms such as a Swan-Jacobs lens are ideal, as high magnification is of benefit. Anterior-segment microinstrumentation is often also helpful to have available in the event of a malpositioned iStent. Early in the incorporation of MIGS into your practice, stringent patient selection will maximize the potential for successful integration of MIGS modalities and will enable a more optimized learning curve. There are several key points to consider in terms of selecting the ideal patient to begin using any of the above-described MIGS devices or modalities upon. Patient selection should begin with the demeanor of the patient. As all of these modalities and surgical approaches will be new to you, having an appropriate patient will be essential. The patient should be cooperative and able to follow the surgeon’s directions, as adequate visualization of the relevant anatomy may require certain head or eye movements on the patient’s part. Furthermore, your early cases may require more surgical time than patients are often used to, and as a result a patient who is aware of the need for attentiveness and cooperation is key. For these MIGS procedures, adequate visualization requires the turning of the patient’s head and eye away from the surgeon (Fig. 40.7). As a result, it is important in early cases to avoid patients with limited cervical mobility or patients with back pain. Fig. 40.2 Typical view of the Trabectome unit performing ab interno cautery and ablation of the nasal trabecular meshwork. Fig. 40.3 A left-facing iStent under direct gonioscopic visualization. For the right-handed surgeon, the left-facing stent is implanted with a “forehand” technique that is often easier. Fig. 40.4 A right-facing iStent under direct gonioscopic visualization. For the right-handed surgeon, implantation of the right-facing stent requires a “backhand” technique that may be slightly more technically challenging.
Deciding on a Minimally Invasive Glaucoma Surgery Procedure
Trabectome
iStent
Patient Selection
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