Local anesthesia (retrobulbar, peribulbar, or sub-Tenon) is administered before the procedure. This can be done in the office if the patient can tolerate a periocular injection while awake.
External cyclodestruction (transscleral cyclophotocoagulation)
There are 2 ways (Video 13-1) to deliver the laser energy externally: by means of discrete treatment spots or broad, continuous application. Discrete delivery is easier to perform but may be associated with more collateral tissue damage. Sweeping application is technically more challenging in patients with tight orbits.
Courtesy of Lauren Bierman, MD.
Scan the QR code or access the video at www.aao.org/bcscvideo_section10.
Discrete transscleral cyclophotocoagulation involves use of a fiber-optic probe to deliver 810-nm diode laser energy through the sclera to the ciliary processes. In this approach, 16–20 treatment spots are applied 360°. The probe is placed so that the energy is delivered posterior to the limbus, in order to target the ciliary processes (Fig 2-13). Care is taken to avoid the 3-o’clock and 9-o’clock positions to prevent damage to the long posterior ciliary nerves.
Continuous transscleral cyclophotocoagulation (MicroPulse; Iridex) also uses 810-nm diode laser energy delivered with a fiber-optic probe. However, the probe is moved in a continuous sweeping manner in applying the energy posterior to the limbus. The laser cycles on and off in a sinusoidal pattern with a duty cycle of 31.3%. A variety of settings are used for continuous transscleral cyclophotocoagulation.
Internal cyclodestruction (endocyclophotocoagulation)
To perform endocyclophotocoagulation (ECP), the surgeon views the ciliary epithelium with an endoscopic probe placed in the ciliary sulcus, posterior to the iris. Laser energy is delivered directly to the target tissue. This procedure is performed in the operating room, often in combination with cataract surgery.
Figure 13-2 Cyclodestruction. The diode laser handpiece attachment (example of 1 manufacturer’s device) is aligned with the limbus and ready to treat.
(Figure developed by Angelo P. Tanna, MD, and illustrated by Wendy Hiller Gee.)
A clear corneal incision is created, and the eye is filled with viscoelastic, with particular attention paid to widening the sulcus. The probe is introduced into the eye, and 0.2–0.5 W of continuous-wave diode laser energy is initially applied to the ciliary processes. The energy is titrated to an endpoint of whitening and shrinking the ciliary processes without rupturing the tissue. The laser is applied in a continuous fashion, treating between 270° and 360° of ciliary processes (if treating 360°, a second incision is required). The effect of the treatment is related to both the amount of energy applied and the distance between the laser probe and the ciliary processes.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.