Glaucoma Surgery – MIGS & Cyclophotocoagulation Procedures

Glaucoma Surgery – MIGS & Cyclophotocoagulation Procedures

February 02, 2021

Cyclophotocoagulation is a laser treatment that targets the ciliary processes of the eye. The ciliary processes are the part of the eye that produce the fluid, or aqueous humor, that bathes the tissues in the front of the eye.

Although the part of the eye that does not function well in glaucoma is the “outflow” or drainage system, including the trabecular meshwork, many treatments target the “inflow” system, such as the ciliary processes which form a ring 360 degrees around the circumference of the eye.

The field of glaucoma has expanded rapidly in the past decade, especially in the area of surgical approaches and procedures. This means that the treating glaucoma surgeon needs to evolve, as do the ophthalmic professional staff, including technicians, surgery schedulers, and operating room personnel.

Let’s discuss recent advances in glaucoma surgery, including minimally invasive glaucoma surgery (MIGS), subconjunctival MIGS, and cyclophotocoagulation and what this means for the entire treatment team.

MIGS

MIGS is a group of procedures otherwise known as angle-based surgery. These include the following:

  • Trabecular bypass stents, such as iStent (Glaukos) and Hydrus (Ivantis)
  • Trabecular removal, such as Trabectome (MicroSurgical Technology), Kahook Dual Blade (New World Medical), and Goniotome (MicroSurgical Technology)
  • Trabecular unroofing, such as gonioscopic-assisted transluminal trabeculotomy, or GATT, and OMNI (Sight Sciences)
  • Schlemm’s canal dilation via ab interno canaloplasty (Ellex)
  • Suprachoroidal stents (since the recall of Cypass, none are currently available, but others are undergoing clinical trials)

A clear distinction should be made between those that are approved for use only with cataract extraction (stent procedures) and those that can be used as stand-alone.

The surgery scheduler needs to ensure that these stent procedures are being performed with cataract surgery or that the patient is aware of billing procedures, if being done “off label” as stand-alone.

This status may change in the near future as trabecular stents are currently being studied for a stand-alone indication. If possible, the patient should be off blood thinners, especially for the trabecular removal and unroofing procedures.

In the operating room, angle-based MIGS require a gonioscopic approach. This means that a goniosurgical lens is used for angle viewing throughout the procedure. The head of the patient is generally tilted away and the microscope tilted towards the surgeon for this approach .

It is essential that the head is able to be turned adequately and is not secured too tightly. It is also generally desirable for the patient to be awake and able to follow directions, as changing head position may awaken and confuse a sleeping patient.

Some procedures may be performed prior to cataract extraction, while others may be done after: make sure to note surgeon preference and if a pupil constricting pharmacologic agent is desired (i.e., Miostat [carbachol intraocular solution, Alcon], Miochol-E [acetylcholine chloride intraocular solution, Bausch + Lomb]).

Postoperative recovery is usually rapid, but vision recovers more slowly than cataract extraction alone. This is due to an increased amount of inflammation and blood reflux into the anterior chamber.

A steroid-induced intraocular pressure (IOP) spike may occur, so many surgeons prefer to use or transition to weaker steroids than prednisolone or Durezol (difluprednate ophthalmic emulsion 0.05%, Novartis).

Subconjunctival MIGS

These MIGS procedures include the Xen gel stent (Allergan) and the Preserflo shunt (Santen), which is predicted for FDA approval in 2020. Both procedures create an artificial drainage pathway from the anterior chamber to the subconjunctival space with the implantation of a device and creation of a bleb.

It is important to make the distinction to the patient between subconjunctival MIGS, which includes bleb-related risks such as infection, hypotony, erosion, and endophthalmitis, and angle-based MIGS, which have significantly reduced risks.

However, these procedures can approach lower IOP targets needed in more advanced disease. The ocular surface should be optimized preoperatively to prevent fibrosis. This entails stopping some glaucoma medications, starting oral carbonic anhydrase inhibitors if needed, and prescribing topical steroids in the week prior if possible.

The use of mitomycin to prevent encapsulation is essential and should be noted by schedulers and OR personnel. The concentration should be decided prior to surgery, unless a reliable system for adjusting concentration is used.

Some surgeons prefer to inject the mitomycin prior to surgery, some at the beginning of the procedure or at the end of the procedure, and others prefer application with sponges via an open conjunctiva technique (optional with Xen, required with Preserflo).

Postoperative care requires the prevention and treatment of hypotony in the short term and maintenance of a bleb in the long term. The former concern can be reduced by patient education to not overexert and to use stool softener. The latter may require more frequent visits as well as bleb needling with antifibrotic (5-fluorouracil or mitomycin) in the clinic or operating room.

Cyclophotocoagulation

These procedures are often performed in the surgical setting, as with endoscopic cyclophotocoagulation (ECP) and micropulse cyclophotocoagulation (MPCPC), although the latter as well as transscleral cyclophotocoagulation (TCP) can be performed in the procedure room of the clinic.

ECP is an intraocular procedure in which the surgical laser endoscope is used to visualize and treat the ciliary processes in order to reduce aqueous production. It is often performed at the same time as cataract extraction but can be performed as a stand-alone procedure in pseudophakic or aphakic patients.

The entry can be via a clear corneal incision or pars plana (performed with vitrectomy). Anterior ECP utilizes viscoelastic to enlarge the sulcus space for visualization, whereas pars plana ECP uses the infusion port.

Viscoelastic should be completely removed by irrigation and aspiration to prevent postoperative IOP spikes. OR staff need to adjust the handpiece where it connects to the laser console in order to focus, adjust power and light, and rotate the image if necessary.

The procedure is performed while looking at a monitor, which needs to be positioned so that the surgeon can view it without turning away from the patient.

To avoid inflammation, steroids are given intravenously, intracamerally, subconjunctivally, or orally during or after the procedure in addition to frequent topical administration. The reusable probes are fragile, and bending them damages the fiberoptic cables leading to degradation of the surgical view.

MPCPC is frequently performed in the OR setting, with heavy sedation and/or retrobulbar anesthesia. If performed in the clinic, a retrobulbar block is performed.

A minority of patients have significant pain in the immediate postoperative period, and can be managed with intravenous or oral non-steroidal anti-inflammatory or narcotic medications. Once this initial period is managed, pain levels are typically well tolerated.

TCP is usually performed in the clinic with retrobulbar anesthesia. Once this wears off, pain levels are usually higher than with MPCPC or ECP and require more robust management of inflammation and pain.

With the recent growth of glaucoma surgical options, patients and surgeons have many choices. Personnel such as clinic staff, surgery schedulers, OR staff, and anesthesiologists need to be aware of these procedures and educate themselves on how to best integrate them into their current work flow. Communication with the surgeon is paramount and ensures the best results for our patients.