Advances in cyclophotocoagulation: Good, better, best

Reviewed by Shan C. Lin, MD

Ophthalmologists have seen a progression in cyclophotocoagulation (CPC), with each generation becoming more doctor and patient friendly. Shan C. Lin, MD, a glaucoma specialist at the Glaucoma Center of San Francisco in California, described the advances in the technology.

Transscleral cyclophotocoagulation

The first attempt at this technology was transscleral cyclophotocoagulation (TCPC), which has its limitations. In some cases, the treatment did not reach the targeted tissue because the tissue was not visualized, and the pars plana often was treated instead. In addition, there was the potential for the surrounding structures to be damaged. Excessive treatment using TCPC can occur and cause an audible popping and explosion of the ciliary processes and pars plana, which can result in inflammation, such as cystoid macular edema (CME).

Introduction of the G-Probe Illuminate Delivery Device (Iridex Corporation) helps to address these problems. This technology uses a diode laser to treat the ciliary processes through the sclera and reduces the IOP by decreasing aqueous production. Lin cited a study1 that reported that the ciliary processes can range from 2.0 to 5.0 mm behind the limbus.

Endoscopic CPC

This is a newer technology that facilitates direct visualization of the ciliary processes as they are being treated. Probes with different gauge sizes (18-, 19-, 20-, and 23-gauge) are available for this intraoperative procedure. In addition, the availability of curved probes allows the treatment of greater area within the same incision, according to Lin. A typical procedure, as he described, is one performed in a patient with pseudophakia through a limbal approach. “The goal is to cause shrinkage and whitening of the ciliary processes,” he said.

A study2 of endoscopic CPC that included a range of glaucoma types found that the IOP decreased from approximately 27 mm Hg preoperatively to approximately 17 mm Hg postoperatively in the 68 patients in the study.

Micropulse technology

This is the newest of the technologies. The Cyclo G6 Glaucoma Laser with the MicroPulse P3 probe (Iridex) is a transscleral procedure designed to deliver laser energy in a pulse pattern to avoid excessive damage to the tissues. This procedure also differs from the G-Probe in that the treatment with the MicroPulse P3 probe is aimed at the pars plana rather than the ciliary processes, and the treatment involves a slow sweeping motion along the superior and inferior limbuses rather than the discreet spot placement of the G-Probe.

An advantage of this new technology is that it can be performed both in an office or the operating room, but Lin prefers performing the procedure in the operating room for increased control and patient comfort. In addition, there are no pops involved with the treatment, and the sweeping motion should avoid the 3 and 9 o’clock positions, according to Lin. “Having slower sweeps with the MicroPulse facilitates better uptake of the laser and efficacy,” he said.

A study3 with follow-up of almost 7 years detailed the long-term efficacy and durability of this treatment. The authors reported a 43% reduction of IOP at 78 months in 14 patients and a concomitant reduction in medications from 1.8 to 1.1. Numerous treatments were needed, with the average of approximately 4.5, to achieve IOP lowering.

Lin also reported results of MicroPulse technology in a retrospective analysis of 54 patients with a baseline IOP of 24 mm Hg, three-quarters of whom had primary open-angle glaucoma. Postoperatively, the average IOP was 17 mm Hg (P = .0002). Success in this study was defined as IOP lowering of 20% or more with or without medications, which was met in 68% of patients. Seven eyes required retreatment.

Complications of the technology include rare unexplained visual loss, hypotony, ocular inflammation, and CME. In assessments using ultrasound biomicroscopy, there were no changes comparing before and after treatment.

MicroPulse works by controlling the thermal effect by chopping a continuous wave of the energy beam into repetitive short pulses interrupted by relaxation times, which makes for less thermal damage to the targeted area.

Iridex recently introduced a new REV-2 probe with a footplate that helps with limbal alignment, improves tissue coupling for better laser delivery, makes the technique easier to perform, and potentially has fewer complications. “Diode TCPC with the G-Probe is typically reserved for blind, painful eyes, and now is available with transillumination,” Lin said.

“Endoscopic CPC can be useful in some cases. However, there are risks associated with penetrating surgery,” he said. “Micropulse TCPC is useful for patients with refractory glaucoma, with less inflammation and possibly less risk than with [the] diode laser.”

Shan C. Lin, MD

E: sl@glaucomasf.com

This article is adapted from Lin’s presentation at the Glaucoma Research Foundation 25th Annual Glaucoma Symposium. Lin is a consultant to Iridex Corporation.

References

1. Agrawal P, Martin KR. Ciliary body position variability in glaucoma patients assessed by scleral transillumination. Eye (Lond). 2008;22(12):1499-1503. doi:10.1038/eye.2008.79

2. Chen J, Cohn RA, Lin SC, Cortes AE, Alvarado JA. Endoscopic photocoagulation of the ciliary body for treatment of refractory glaucomas. Am J Ophthalmol. 1997;124(6):787-796. doi:10.1016/s0002-9394(14)71696-4

3. Chew P, Aquino MC. Long-term efficacy of micropulse diode transscleral cyclophotocoagulation in the treatment of refractory glaucoma. Abstract presented at: 12th European Glaucoma Society Congress; June 19-22, 2016; Prague, Czech Republic