Cyclophotocoagulation is indicated for patients with refractory glaucoma who have failed trabeculectomy or tube shunt procedures, patients with minimal useful vision and elevated intraocular pressure, and patients who have no visual potential and need pain relief (based on Level III evidence).
It may be useful for patients whose general medical condition precludes invasive surgery or who refuse more aggressive surgery (i.e., filter or tube). It is also useful in emergent situations, such as the acute onset of neovascular glaucoma.
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 cyclophotocoagulation laser treatment causes the ciliary processes to shrink, resulting in less aqueous humor production and lower eye pressure. However, the ciliary processes can regenerate, so sometimes the procedure needs to be repeated.
Transscleral cyclophotocoagulation (TCPC) was the first attempt at this technology, 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. Introduction of the G-Probe Illuminate Delivery Device (Iridex) helps address these problems.
This latest generation of the technology allows identification of the ciliary process locations either before or at the time of treatment. The ciliary processes can range from 2.0 to 5.0 mm behind the limbus.
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.
The goal is to cause shrinkage and whitening of the ciliary processes. A study of endoscopic CPC that included a range of glaucoma types found that the IOP decreased from approximately 27 mm Hg preoperatively to 17 mm Hg postoperatively in the 68 study patients.
The numbers of medications decreased from approximately 3 to 2. The complications associated with endoscopic CPC included fibrin exudate (24%), hyphema (12%), cystoid macular edema (CME) (10%), vision loss (6%) due to CME in most cases, and choroidal detachment (4% 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. An advantage of this new technology is that it can be performed both in an office or the operating room.
Doctors mostly prefer performing the procedure in the operating room for increased control and patient comfort. There are no pops involved with the treatment, and the sweeping motion should avoid the 3 and 9 o’clock positions.
A study with follow-up of almost 7 years reported the 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.
A number of treatments were needed, with an average of 4.5, to achieve IOP lowering.
According to the results of MicroPulse technology in a retrospective analysis of 54 patients with a baseline IOP of 24 mm Hg, 75% 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 of the eyes required retreatment. The potential complications of the technology include rare, unexplained visual loss; hypotony; ocular inflammation; and CME.
In anatomic assessments using ultrasound biomicroscopy, there were no observable 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.
The technology also is thought to stimulate biologic factors, such as cytokines and growth factors, at the treatment 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.
Endoscopic CPC can be useful in some cases; however, there are risks associated with penetrating surgery.