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MicroPulse laser treatment considered option for DME
Laser combines continuous wave with a series of short repetitive pulses to significantly improve visual acuity.
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MicroPulse laser treatment is a repeatable procedure in patients with diabetic macular edema because it stimulates retinal pigment epithelium without causing lesion or burn to the fovea, according to one user of the technology.
Sergio Rojas, MD, surgical director at Clínica de Retina y Vítreo Cuernavaca in Cuernavaca Morelos, Mexico, has used the IQ 577 nm laser (Iridex) with MicroPulse to treat approximately 60 patients with DME. He believes MicroPulse to be an “excellent option” in cases of significant DME with or without hard exudates with leakage verified by fluorescein angiography and absent hyaloid thickening, even if the patient may have previously received anti-VEGF injections.
“Given the fact that MicroPulse does not interact negatively with the injections, I believe that the laser actually increases the efficacy of injections and reduces the number of injections,” Rojas said.
Both a conventional laser with continuous wave and MicroPulse stimulate the retinal pigment epithelium, “favoring the production, modulation and expression of intracellular biological factors,” Rojas told Ocular Surgery News. These factors, which include beta-actin and the stromal cell-derived factor 1, upregulate the retina architecture and improve the hematoretinal barrier, “acting as very potent anti-VEGF,” he said. Two of the important anti-VEGFs present in this process are pigment epithelium-derived factor and thrombospondin-1.
Procedure
In a clinical setting, the patient is first seated comfortably. The laser is set in conventional (continuous wave) mode, with 200 ms of duration, 200 µm of spot diameter and 50 mW of power. Rojas uses a Volk TransEquator lens. Next, a series of test shots (burns) are performed, with increasingly adjusted power until a third-degree burn is observed.
The MicroPulse mode is then selected, with 5% duty cycle. The proper power is determined by tripling the conventional mode power of the test shot (eg, 120 mW × 3 = 360 mW).
“We use a maximum of 400 mW,” Rojas said.
Once the power is set, a 7 × 7 grid is selected in the TxCell Scanning Laser Delivery System (Iridex).
“The spacing for the 7 × 7 grid is 0, or confluent, to cover the entire area with as many spots as possible,” Rojas said.
The average number of laser pulses, or shots, for a standard treatment is between 300 and 400.
“The MicroPulse laser helps improve the macular architecture and, thus, visual acuity,” Rojas said. “There is also a nonsignificant improvement in macular volume.”
If the first therapy session is successful, Rojas recommends re-treatment at 3 months. To increase the likelihood of success when using MicroPulse to treat DME, Rojas also advocates that the laser not be applied in cases of hyaloid thickening or in patients with severe kidney conditions, uncontrolled hypertension or severe dyslipidemia.
Follow-up
Rojas and colleagues have conducted 1-year follow-up in eight patients with DME who underwent the laser treatment. Mean visual acuity initially was 0.49 logMAR, which at 6 months after treatment improved to 0.3 logMAR, a statistically significant difference (P = .05). In addition, mean central macular thickness decreased from 315 µm to 291 µm, but this was not a statistically significant difference.
“Patients with greater decrease in central macular thickness were those who showed a significant improvement in visual acuity,” Rojas said. In most patients, visual acuity increased an average of six ETDRS letters.
“All study patients have remained without any complications or lesions caused by MicroPulse,” Rojas said. “Overall, visual acuity results and retinal/macular architecture improvement compare favorably with the results that have been reported in publications worldwide.”
Rojas and colleagues are pursuing two follow-up studies of the MicroPulse laser, one involving patients without previous DME treatment and the other combining the laser with anti-VEGF injections. – by Bob Kronemyer