Slow-Coagulation Continuous-Wave Cyclophotocoagulation

 

Slow coagulation CW-TSCPC is an emerging relatively noninvasive intervention that can be used in different patient populations. The procedure uses the traditional G-probe and continuous wave (CW) laser, with a modified balance of power and duration for enhanced safety compared to the conventional protocol.

Slow coagulation CW-TSCPC delivers photocoagulative laser energy to the ciliary body using a fixed lower power of energy over a longer duration, thereby theoretically decreasing the risk of collateral damage surrounding the ciliary body and severe inflammation from necrotic high energy disruption of the ciliary body.

The greater pressure-lowering effect observed with SC-CPC may be attributed to more substantial structural changes in the ciliary body, whereas the micropulse (MP) technique does not appear to produce significant histologic changes.

The standardized technique involves the following parameters: 1250 mW, 4 s/spot, 20 spots, delivering a total energy of 100 J.

The recently described variation—the Double-Arc Slow-Coagulation protocol—employs a dual-row application strategy, divided in upper (ciliary body shadow) and lower (1.5 mm behind) arcs. Initial results with this technique have demonstrated favorable IOP control and a low rate of complications in the management of refractory glaucomas.

The most frequent complications reported in a study comparing SC-CPC with MP-LT are clinically significant visual acuity loss (20.0% in the SC-CPC group and 26.7% in the MP-LT group), transient anterior segment inflammation (30.0% vs. 23.3%), and transient corneal edema (13.3% vs. 20.0%). 

Pupillary abnormalities, cystoid macular edema, iris synechiae, and iris neovascularization occur with varying frequencies. Hypotony has been reported in 6% patients following SC-CPC.

Pupillary abnormalities are often linked to a more anterior application of the laser, closer to the iris root.

A two-center, randomized, clinical trial in a population of patients with refractory glaucoma, SC-CPC demonstrated superior IOP control, with fewer IOP-lowering medications and a lower rate of surgical failure compared to MP-LT over an 18-month follow-up. Fewer reapplications and additional surgeries were required in the SC-CPC group.

Another study of pseudophakic glaucoma reported lowering of IOP from 27.5±9.8 mm Hg preoperatively to 16.1±6.3 mm Hg postoperatively with a mean percentage reduction of IOP of 42.1% and 75.7% of eyes having ≥20% decrease in their baseline IOP.

Another study in virgin eyes reported that 52.2% of the treated eyes had ≥20% reduction of IOP from baseline. Interestingly, the IOP reduction was noted to more in patients with higher baseline IOP (>21 mm Hg). Slow coagulation TSCPC treatment resulted in a significant decrease of glaucoma medications from 3.8±1.0 to 2.8±1.4 at baseline and last visit, respectively. 

These findings highlight SC-CPC as a reliable technique for managing different types of patients with glaucoma.