Subthreshold diode-laser micropulse photocoagulation as a primary and secondary line of treatment in management of diabetic macular edema

Abstract

BackgroundThe purpose of this study was to evaluate subthreshold diode-laser micropulse (SDM) photocoagulation as a primary and secondary line of treatment for clinically significant diabetic macular edema (CSDME).MethodsIn this prospective nonrandomized case series, 220 cases of nonischemic CSDME were managed primarily and secondarily by SDM photocoagulation on a 15% duty cycle with a mean power of 828 mW and a spot size of 75–125 μm. SDM treatment was repeated at 3–4-month intervals if residual leakage was observed. Additional intravitreal pharmacologic therapy was used according to the response. Follow-up varied from 12 to 19 (mean 14±2.8) months. Novel software designed by the authors was used to record the subvisible threshold laser applications and their parameters on the fundus image of the eye. Evaluation of the results of treatment was done using fluorescein angiography and optical coherence tomography (OCT). Primary outcome measures included changes in visual acuity and foveal thickness at OCT. Secondary outcome measures included visual loss of one or more Snellen lines and laser scars detectable on fundus biomicroscopy or fluorescein angiography.ResultsIn the primary treatment group, there was significant improvement or stabilization of visual acuity after the first 3–4 months, which was stable thereafter. Visual acuity was stable in the secondary treatment group. A corresponding reduction of macular thickness on OCT was noted during the follow-up period in both groups. Additional therapy included repeat SDM photocoagulation, intravitreal injection of triamcinolone, and pars plana vitrectomy. Laser marks seen as changes in retinal pigment epithelium on fundus biomicroscopy and fluorescein angiography were noted in 3.3% and 5.7% of cases. Our novel software could accurately record the location of all SDM-invisible applications.ConclusionMicropulse laser is an effective minimal intensity therapy that offers the clear advantage of minimizing or avoiding laser-induced visible retinal burn/scarring while reducing the foveal thickness in the management of selected cases of CSDME. Future prospective studies should include the use of SDM photocoagulation as a combined minimally invasive therapy to consolidate the prompt but temporary effects of anti-vascular endothelial growth factor or anti-inflammatory agents. Virtual localization of SDM-invisible applications using our proprietary software could be used to guide further retreatments.

A Review of Subthreshold Micropulse Laser for Treatment of Macular Disorders

“…In the majority of studies no laser scars occurred after SML. Four studies reported scar formation or pigmentary changes in a small amount of eyes after SML treatment [ 48 , 50 , 51 , 54 ]. Retinal changes were only observed in eyes treated with duty cycles of 15%; lower duty cycles did not lead to scar formation in the listed studies.…”

“…As a result of the small number of studies and the variety in control groups (bevacizumab, SML + triamcinolone, conventional laser), the control groups were not separately analyzed. Only one study [ 48 ] had a control group where patients were treated with anti-VEGF agents, the current standard therapy for macular edema due to BRVO.…”

Effects of subthreshold diode micropulse laser photocoagulation on treating patients with refractory diabetic macular edema

“…Subthreshold diode micropulse laser photocoagulation has these two properties. Few studies have evaluated the effects of this type of laser photocoagulation on improving VA and DME with less laser-induced chorioretinal damage 11 . In some studies, a combination of laser treatment and medication, such as dexamethasone, was effective and safe for the treatment of resistant DME 12 …”

Yellow Pattern 577-nm Micropulse Laser: Treatment of Macular Edema from Radiation Retinopathy – A Case Report

“…Subthreshold micropulse laser is an innovative therapy for retinal disorders which has been shown to be safe and effective in the treatment of macular edema [ 6 , 7 ]. The yellow pattern 577-nm micropulse laser in this case converts each laser shot into a “pulse envelope” consisting of a sequence of extremely short pulses of laser (10–20 ms) with intervening periods of zero laser energy to the treatment site.…”