Myths of MicroPulse transscleral laser therapy
By Jella An, MD
MicroPulse transscleral laser therapy (MicroPulse-TLT; Iridex Corporation) is a safe, effective,1-4 and innovative approach to treating and managing glaucoma. Non-incisional and virtually pain-free, MicroPulse-TLT stimulates the ciliary body morphology to allow for increased uveoscleral outflow2, an entirely different, and safer4-6 mechanism of action than its predecessor, a cyclodestructive ablative procedure.
Debunking the myths
Many of us have either had, or at least have heard about, bad experiences using traditional continuous wave-transscleral cyclophotocoagulation (CW-TSCPC), and although MicroPulse-TLT is completely different in energy delivery and tissue targeted, a cloud of suspicion continues to linger. Consequently, MicroPulse-TLT has been relegated towards the end of the treatment paradigm causing us to forfeit the benefits available to patients by employing it earlier. Here are five common myths that it is time to debunk.
1. MicroPulse-TLT should be reserved for patients with poor visual potential. It is very rare for a patient to lose vision due to this treatment.
In fact, one can argue that it is safer than any incisional surgery, including MIGS, given the low risk of infection, hyphema, or hypotony.7,8 A recent publication concluded no loss of acuity from the procedure in 61 eyes of 46 patients studied.1 We can potentially preserve a patient’s vision at earlier disease stages.1,2,9,10
2. MicroPulse-TLT should not be performed prior to filtering surgery because it causes subconjunctival scarring.
I have performed many MicroPulse laser procedures with the Cyclo G6 Glaucoma Laser and MicroPulse P3 probe (Iridex) that I later followed with XEN Gel Stent (Allergan), tubes, or trabeculectomy. I have not observed or been impeded by subconjunctival scarring on any of these patients. In my experience, burn or scarring of the conjunctiva is extremely rare and inflammation is mild and transient. MicroPulse-TLT does not burn bridges for surgery choices later.1,8
3. MicroPulse-TLT leads to significant inflammation and requires long-term steroid use postoperatively.
Some degree of inflammation can accompany all ocular procedures; however, inflammation following MicroPulse-TLT is relatively mild and short-lived due to the gentle, non-invasive procedure.1,7,8,11 I either prescribe a topical corticosteroid for one week or a give single intraocular injection of 0.4 cc of dexamethasone at the completion of the procedure. After performing over 200 MicroPulse-TLT procedures, none of my patients has returned with inflammation when the proper setting and technique was used.
4. Total duration of energy delivery is the only variable you can control.
Absolutely false; everything from the duty cycle to the power to the use of a coupling agent is a variable. When it comes to settings, until you have performed more than 20 cases, I recommend sticking with the recommended settings of 2000mW power using a 31.3% duty cycle with five passes over 80 seconds per hemisphere (about 8-10 seconds per quadrant). Because settings can vary, I teach all of my residents to write down their preferred settings, attach them to the machine, and always double-check the laser settings before using it to confirm nothing was changed. This protects you from potentially causing damage or undertreatment if others changed the parameters to higher or lower settings without your knowledge.
5. MicroPulse-TLT allows the surrounding collateral tissue to cool; therefore, it is safe to increase energy settings until you hear a “pop” to titrate.
That is a practice that gets confused with traditional CW-TSCPC in which we wait for a pop and then titrate down. Please don’t! There is no need to titrate MPCPC intraprocedure when you use the recommended settings. After you have broader experience you can make adjustments, but still, no pops. I prefer to use a slightly higher power because in my hand and my patient population, it is what works best; however, your experience level and patient needs will determine the best settings.
Shifting our thinking—shifting the paradigm
Now that we understand that MicroPulse-TLT delivers strong efficacy with a benign safety profile in contrast to higher risk traditional CW-TSCPC, it is time to rethink and reorder the treatment paradigm. Patients who have already failed MIGS or incisional surgeries are now our starting point for MicroPulse laser treatments. MicroPulse-TLT is extremely safe, but it is not aggressive—it is not the “big gun.” MicroPulse therapy has been an excellent option to fill the gap between MIGS and more aggressive surgeries; however, I encourage physicians to consider using it during earlier disease stages rather than reserving it for refractory or late-stage glaucoma.1,4,10 Think of MicroPulse-TLT as the MIGS of CW-TSCPC. There are many advantages of MicroPulse-TLT including:
- Delays incisional surgery
- No activity restrictions
- Quick visual recovery
- Fewer follow-up visits
- Can avoid postoperative drops if intraocular injection is used
- Minimal risk of infection or other complications 1,4,6
- Repeatable since there is no cellular destruction 4,5
- Quick (under 5 minutes)
There are some disadvantages for your patients to consider. First, this is not an instant fix; it can take up to 5 weeks to maximally lower IOP. During early-stage disease, patients who are maxed out on medications and have a high IOP, they are likely to need to continue their meds even after they see a reduction in IOP to achieve their target. Only patients who are well controlled on multiple medications should be told that the surgery could reduce their reliance on topical and/or oral medications.3,8,10-13 I find that my patients are most comfortable with peri-bulbar anesthesia of lidocaine and bupivacaine, with or without sedation. Finally, the durability of IOP reduction has known limits. The majority of patients will require follow-up treatment (or an “enhancement”) in one to two years, and studies have shown success in repeat treatments controlling IOP levels for over 6 years.
MicroPulse-TLT is effective and deserves consideration earlier in the treatment paradigm. With minimal risk to visual acuity or impediment to future surgeries, we are obligated to offer them this option and the opportunity to preserve their vision and their quality of life.
Jella An, MD, specializes in glaucoma treatment at the Mason Eye Institute, University of Missouri. Dr An reports she is a paid speaker for IRIDEX.
References
1. Yelenskiy A, et al. Patient Outcomes Following MicroPulse Transscleral Cyclophotocoagulation Intermediate-term Results. J Glaucoma. 2018;27(10):920-925.
2. Barac R, et al. Choroidal Thickness Increase after MicroPulse Transscleral Cyclophotocoagulation. Romanian J Ophthalmol. 2018;62(2):144-148.
3. Awoyesuku EA, et al. Outcome of Micropulse Laser in Treatment of Open Angle Glaucoma in a Peripheral Hospital in Rivers State, Nigeria: Our Initial Experience. Journal of Advances in Medicine and Medical Research. 2019;29(2):1-7.
4. Nguyen AT, et al. Early Results of MicroPulse Transscleral Cyclophotocoagulation for the Treatment of Glaucoma. Eur J Ophthalmol. 2019;1120672119839303 published online ahead of print.
5. Abdelrahman AM, et al. Micropulse versus Continuous Wave Transscleral Cyclophotocoagulation in Refractory Pediatric Glaucoma. J Glaucoma. 2018;27(10):900-905.
6. Aquino MC, et al. Micropulse versus Continuous Wave Transscleral Diode Cyclophotocoagulation in Refractory Glaucoma: A Randomized Exploratory Study. Clin Exp Ophthalmol, 2015;43(1):40-6.
7. Subramaniam K et al. Micropulse Transscleral Cyclophotocoagulation in Keratoplasty Eyes. Cornea. 2019;38(5):542-545.
8. Zaarour K, et al. Outcomes of Micropulse Transscleral Cyclophotocoagulation in Uncontrolled Glaucoma Patients. J Glaucoma 2019;28(3):270-275.
9. Varikuti VNV, et al. Outcomes of Micropulse Transscleral Cyclophotocoagulation in Eyes with Good Central Vision. J Glaucoma, 2019;28(10):901-905.
10. Al Habash A, Al Ahmadi AS. Outcome of MicroPulse® transscleral photocoagulation in different types of glaucoma Clin Ophthalmol, 2019;132353-2360.
11. Souissi S, Baudouin C, Labbe A, Hamard P. Micropulse transscleral cyclophotocoagulation using a standard protocol in patients with refractory glaucoma naive of cyclodestruction. Eur J Ophthalmol, 2019;1120672119877586.
12. Jammal AA, et al. Prospective Evaluation of Micropulse Transscleral Diode Cyclophotocoagulation in Refractory Glaucoma: 1 Year Results. ArqBras Oftalmol. 2019;82(5):381-388.
13. Sarrafpour SS, et al. Evaluating the long-term effects of micropulse cyclophotocoagulation on glaucoma patients Invest Ophthal Vis Sci., 2018;59(9):6103-6103.
