Micropulse transscleral diode laser cyclophotocoagulation an option for refractory glaucoma

Advantages include a good safety profile and minimal postoperative inflammation and hypotony.

Issue: February 10, 2016

ByThomas TJ John, MD

Glaucoma can be a difficult management problem in a subset of patients, even for the most experienced glaucoma specialists. The treatment spectrum includes drugs, trabeculoplasty, microincision glaucoma surgery and traditional glaucoma surgery.

While many use glaucoma medications as their initial treatment modality, others use selective laser trabeculoplasty for the initial IOP control. The majority of glaucoma patients’ IOPs may be controlled with one or more topical medications, but there is a subset of patients whose IOPs are not adequately controlled even on maximum medical therapy. Additionally, some patients have limited choice of glaucoma medications due to allergy to glaucoma medications, and others may have compliance issues, all of which may contribute to elevated IOPs and progressive visual field loss. This subset of patients with uncontrolled IOP and/or progressive visual loss often requires surgical intervention.

Surgical interventions are primarily divided into those that facilitate egress of aqueous from the eye to the exterior and a few procedures that focus on decreasing the ingress of aqueous. Excessive egress of aqueous often introduces multiple postoperative complications including hypotony, maculopathy, corneal edema and other surgery-related complications such as hyphema and infection. Previously, the main procedure that decreased ingress of aqueous was cyclocryotherapy, but because it was often not adequately titratable with regard to the level of IOP reduction and it was associated with increased postoperative inflammation, it became a less desirable procedure for ophthalmic surgeons.

In this column, I describe a relatively new surgical technique, namely micropulse transscleral diode laser cyclophotocoagulation for glaucoma management, which decreases IOP with a possible dual mechanism of targeting the ciliary processes and increasing the uveoscleral outflow.

Laser system

A transscleral diode laser, the Cyclo G6 laser system (Iridex) with a P3 probe, is used for this procedure. The laser settings are 2,000 mW at 80 second arc treatment each, with a total of two arcs to complete the treatment.

Figure 1. Inferior half is treated using the P3 probe.

Figure 2. Distal extent of treatment of the inferior half, and then it is repeated until 80 seconds of treatment has been delivered.

Figure 3. Superior half is treated with the notch of the probe (arrow) aimed toward the central cornea, while the base is seated on the conjunctival surface at the limbus.

Figure 4. Superior half treated with the P3 probe.

Figure 5. Superior extent of the arc treatment. This is then repeated for the total duration of 80 seconds.

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Surgical technique

I use the operating room with the patient under monitored anesthesia care for increased patient comfort during the procedure. A short surgical drape is optional, while periocular surgical prep is usually not required. Two percent lidocaine jelly to neutralize superficial conjunctival sensations may be used, while monitored anesthesia care provides the required patient comfort during the laser treatment. I use the P3 probe, which has a notch that is directed toward the central cornea, and the probe base is seated at the limbus over the conjunctival surface (Figures 1 to 5). It is then moved in a slow and steady manner, both clockwise and counterclockwise, until the 80 seconds have lapsed (Figures 2 to 5). This may be started in the superior or inferior half over the horizontal 180° axis. A second arc is then performed in the untreated area to complete the treatment session. The 3 and 9 o’clock positions may be left untreated. This methodology applies laser for half a millisecond followed by 1.1 milliseconds of rest pattern. Topical steroid and cycloplegic drops are used, and the eye is not patched.

Postoperative follow-up

The patient is seen the next day, and vision, IOP and slit lamp examinations are carried out. The amount of postoperative inflammation is usually minimal. Postoperatively, topical prednisolone acetate 1% drops are used four times a day and atropine 1% drops are used twice a day. Atropine is discontinued at 1 week, while the topical steroids are tapered and stopped.

Comments

The advantages of this new procedure include what appears to be a good safety profile. It is non-incisional, and because it is an extraocular procedure, usually postoperative inflammation is minimal. It is repeatable, and other glaucoma treatment modalities can be performed. Unlike cyclocryotherapy and continuous wave transscleral diode cyclophotocoagulation, the risk of possible hypotony is minimal. While it appears to be a promising procedure in glaucoma management, larger series of patients and long-term follow-up are essential to evaluate the overall safety, efficacy and reproducibility of this relatively new surgical procedure.

References:
Aquino MC, et al. Clin Experiment Ophthalmol. 2015doi:10.1111/ceo.12360.
John T, Crandall AS. Glaucoma. In: John T, ed. The Chicago Eye and Emergency Manual. New Delhi, India: Jaypee Brothers Medical Publishers; 2011:155-186.
Kuchar SD, et al. Lasers Med Sci. 2015;doi:10.1007/s10103-015-1856-9.
Tan AM, et al. Clin Experiment Ophthalmol. 2010;doi:10.1111/j.1442-9071.2010.02238.x.

For more information:
Thomas “TJ” John, MD, a clinical associate professor at Loyola University at Chicago and in private practice in Oak Brook, Tinley Park and Oak Lawn, Ill., can be reached at tjcornea@gmail.com.

Disclosure: John reports no relevant financial disclosures.