Micropulse transscleral cyclophotocoagulation (TSCPC) with a diode laser (Cyclo G6 Glaucoma Laser System, Iridex) is demonstrating promising efficacy with better safety and tolerability than traditional TSCPC.
The early experience with this approach suggests the potential for broadening the role of cyclophotocoagulation in the glaucoma treatment paradigm, said E. Randy Craven, MD, at the Glaucoma Symposium during the 2017 Glaucoma 360 meeting.
“The micropulse procedure can be done using only a limited peribulbar or retrobulbar block to achieve comfort,” said Dr. Craven, associate professor, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, and chief of glaucoma, King Khaled Eye Specialist Hospital (KKESH), Riyadh, Saudi Arabia. “Because it is less painful than standard TSCPC, we have been able to prepare to transition these cases to a minor procedure room.”
Dr. Craven said this procedure will be beneficial for decreasing operating room utilization at KKESH, considering 10 to 15 standard TSCPC procedures are performed there weekly.
“Furthermore, we are not seeing hypotony and phthisis after micropulse TSCPC, which are significant risks with continuous wave TSCPC,” he added. “Because of its favorable safety, the micropulse procedure is not only an option for treating end-stage glaucoma and in pseudophakic eyes, but that it may be used in phakic eyes, as a supplemental procedure in eyes with a prior tube, and for patients on anticoagulant therapy who are at risk for intraocular hemorrhage with a filtration procedure.”
How it performs
The micropulse procedure is performed with a novel contact probe (MicroPulse P3 Glaucoma Device, Iridex) that delivers the laser energy with a 31.3% duty cycle (0.5 ms on time, 1.1 ms off time) using a continuous motion or “sweep” over the treatment site. By delivering energy in bursts, the micropulse technique allows tissue to cool between pulses, thereby minimizing damage.
The tip design of the probe used to perform micropulse TSCPC supports a sweeping motion and the treatment is applied in two arcs from the 9:30 to 2:30 and 3:30 to 8:30 clock positions. Dr. Craven noted that exact algorithms for micropulse TSCPC are being developed and should be available soon.
“Currently, most (physicians) doing this procedure are setting the energy at 2000 mW and then varying the total sweep time duration between 100 and 320 seconds, depending on such parameters as iris pigmentation and the disease characteristics,” Dr. Craven said. “Unlike continuous wave TSCPC, there is no ‘pop’ that indicates the treatment endpoint.”