Subthreshold yellow micropulse laser for treatment of diabetic macular edema: Comparison between fixed and variable treatment regimen

Abstract

Purpose: To compare the efficacy between fixed and variable treatment regimens of subthreshold yellow micropulse laser for the treatment of diabetic macular edema. Methods: This is a retrospective, comparative, 12-month study of 39 eyes: 24 eyes received fixed treatment regimen of subthreshold micropulse laser treatment and 15 eyes underwent variable treatment regimen of subthreshold micropulse laser, all eyes were followed up for 12 months. Subthreshold micropulse laser was performed with the following parameters: 100 μm spot size on slit lamp, 5% duty cycle of 0.2 s, and 250 mW power. To choose the power of the variable treatment regimen of subthreshold micropulse laser group, continuous laser power was titrated to a barely visible burn and then switched to MicroPulse mode, multiplying the test burn power by 4 and using a 5% duty cycle of 0.2 s. Main outcomes included changes in central macular thickness and best-corrected visual acuity. Results: At baseline, the mean LogMAR best-corrected visual acuity was 0.297 ± 0.431 in the variable treatment regimen of subthreshold micropulse laser group and 0.228 ± 0.341 in the fixed treatment regimen of subthreshold micropulse laser group. At the end of follow-up, the mean LogMAR best-corrected visual acuity was 0.289 ± 0.473 (p = 0.785) and 0.245 ± 0.376 (p = 0.480) in the variable and fixed treatment regimens of subthreshold micropulse laser groups, respectively. Similarly, central macular thickness decreased in both groups after treatment; at baseline, the mean central macular thickness was 371.06 ± 37.8 in the variable treatment regimen of subthreshold micropulse laser group and improved to 325.60 ± 110.0 μm (p = 0.025) at the end of the follow-ups, while it was 342.30 ± 35.4 in the fixed treatment regimen of subthreshold micropulse laser group and improved to 308.51 ± 67.5 (p = 0.037). Conclusion: Both treatment regimens are effective for the treatment of mild center-involving diabetic macular edema: fixed treatment appears more suitable minimizing treatment time and reducing the possible errors due to wrong titration in the switch from continuous to micropulse mode.

Subthreshold Micropulse Laser in Diabetic Macular Edema: 1-Year Improvement in OCT/OCT-Angiography Biomarkers

“…[1][2][3][4][5][6] SMPL does not induce protein coagulation, and, therefore, prevents formation of retinal scars and tissue damage. 1,7 Even if SMPL has proven to be an effective treatment for diabetic macular edema (DME), in terms of visual function improvement/stabilization and macular thickness decrease, 3,4,[8][9][10][11][12][13][14][15] the exact mechanism of action is still under investigation. Retinal pigment epithelium (RPE) has been considered the main target with the consequent release of "heat shock proteins" (Hsps), in particular Hsp 70.…”

“…The clinical effects of SMPL on the retina in eyes with DME have been evaluated using standard imaging techniques, such as color fundus photography, optical coherence tomography (OCT), fundus autofluorescence (FAF), fluorescein angiography (FFA), and microperimetry. 3 , 4 , 9 – 11 , 15 However, only one study reported on the use of OCT angiography (OCTA) in evaluating microvascular changes occurring after SMPL treatment in DME. 18 In that study, our group documented early significant changes in some microvascular parameters (decrease in the area of FAZ, number of microaneurysms (MAs), and intraretinal area of cysts), in particular in the deep capillary plexus (DCP), during 6 months of follow-up after SMPL.…”

Diabetic Macular Edema Treated with 577-nm Subthreshold Micropulse Laser: A Real-Life, Long-Term Study

“…The cornerstones of subthreshold retinal laser therapy were established and defined using an 810-nm near-infrared micropulse laser [ 15 , 16 ]. The 577-nm yellow laser was later introduced and, although at present it is the most commercially available device, its efficacy has been evaluated by fewer studies involving smaller sample sizes and shorter follow-up periods [ 9 , 13 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. At present, a wide array of different duty cycle durations, spot sizes and power settings are employed by different clinicians, limiting, in our opinion, the diffuse clinical application of this technique [ 4 , 9 , 10 , 19 ].…”

“…A recent analysis compared fixed parameters treatment and titrated treatment for 577-nm yellow laser: the first one was recommended based on its greater speed of setup and the implicit avoidance of any possibility of titration errors [ 13 ]. Titration has also been discouraged due to the absence of any reliable, safe and scientifically-validated titration algorithms [ 23 ].…”

“…Prior to treatment, topical anesthesia with proparacaine 0.5% drops was administered. Yellow micropulse laser was delivered through an Ocular Mainster Focal/Grid lens (Ocular Instruments, Washington, DC, USA) using the Iridex IQ 577 (Iridex Corporation, Mountain view, CA, USA) instrument, with the following standard settings: spot size of 100 μm, power of 250 mW, duration of each spot 200 ms and 5% duty cycle, as previously described [ 9 , 13 ]. Confluent, non-overlapping spots, were applied over the whole macular area.…”