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Micropulse for Retinal Diseases

Micropulse technology is a laser delivery method that adds a new dimension of control over laser output facilitating tissue-sparing applications. Unlike conventional photocoagulation where continuous wave laser output causing rapid temperature rise, micropulse laser emission is chopped into a train of ultra short pulses. Such short laser pulses will affect the RPE with minimal effects on photoreceptors and the sensory retina. This method of laser delivery markedly limits the overall laser- induced heat spread to adjacent tissues. Numerous studies have shown micropulse laser to be effective for the treatment of a variety of retinal conditions including diabetic macular edema, macular edema associated with vein occlusions, central serous retinopathy and proliferative diabetic retinopathy.

NRI is currently involved in the following micropulse projects:

Subvisible Micropulse Laser for Neovascular Age Related Macular Degeneration 

Several studies have demonstrated that laser application to RPE cells induces altered expression of locally acting cytokines. There is a possible therapeutic role for naturally occurring endogenous cytokines induced by laser that may inhibit choroidal neovascularization. MicroPulse diode laser has shown efficacy in the treatment of several retinal diseases including diabetic retinopathy and branch retinal vein occlusion presumably by stimulating RPE cells and changing their microenvironment. The aim of this study is to explore potential treatment benefits of micropulse laser application in wet AMD.

Comparison of Wavelengths in Subvisible Micropulse Laser Treatment of Diabetic Macular Edema 

Subvisible micropulse diode laser with an 810 nm wavelength has been shown to be as effective as conventional photocoagulation in resolving diabetic macular edema without causing visible retinal damage 8-11. Subvisible micropulse laser with a 577 nm wavelength is newly available. To our knowledge there is no published data comparing the efficacy of these two wavelengths for the treatment of diabetic macular edema. The goal of this study is to compare treatment effects of 810 nm and 577 nm subvisible micropulse lasers in diabetic macular edema.

Pre-Micropulse 

DMascular Pre

Left picture shows diabetic macular edema VA 20/100. 

Post -Micropulse

DMascular Post

Right picture shows significant reduction of DME two months after application of micropulse laser. VA 20/30. There is no sign of retinal burn or scar formation

 

CSCR remains an idiopathic disorder without a definitive etiology. Many cases of CSCR resolve after a period of observation without any treatment. In refractory cases, treatment options have included focal laser treatment, photodynamic therapy, and intravitreal anti-VEGF medications. Focal thermal laser photocoagulation at the site of RPE decompensation has been shown to promote resolution of the serous detachment in CSCR. Conventional laser applies a thermal burn to the retina and exposes the patient to risks of focal burn, scotoma, long-term focal scar expansion, choroidal neovascularization, and potential new sites of leakage.

Subvisible micropulse laser has been shown to avoid the risks of conventional laser with the potential of improving retinal edema in diabetic macular edema and branch retinal vein occlusion. Application of micropulse laser in the setting of central serous chorioretinopathy has been limited to case reports and a case series. Studies have utilized test burns and subthreshold micropulse laser with duty cycles of 15%. Both the test burns and higher duty cycles have been documented to cause mild RPE alterations secondary to local heating, visible clinically and on fundus, infrared, and autofluorescence imaging, despite “care” to avoid such changes.

In this study, we investigate the efficacy of subvisible micropulse laser at a predetermined laser power (950 mW) and lower duty cycle (5%) for treatment of CSCR. The lower settings may allow for truly subvisible treatment as evaluated by clinical and diagnostic studies.

 

Examples
Pre Micro2

Pre-Micropulse 

Persistent (8 months) subretinal fluid in a patient with CSCR: VA 20/80.

Post Micro_2

Post-Micropulse

14 days post treatment: VA 20/20. No signs of laser treatment. No leakage.

Subvisible MicroPulse Laser for Central Retinal Vein Occlusion (CRVO) 

Subvisible micropulse laser has shown benefit in the treatment of retinal vascular disease such as diabetic macular edema and branch retinal vein occlusion by decreasing macular edema and improving visual acuity. The likely mechanism of action is production of endogenous anti-VEGF agents. As far as we know, subvisible micropulse laser has never been studied in the treatment of CRVO. The aim of this study is to evaluate potential benefits of subvisible micropulse laser in CRVO

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The two pictures on the left  show OCT and fluorescein angiography of a patient with CRVO, pre-treatment. Vision is 20/40. Note cystoid macular edema (CME) and fluorescein leakage in the temporal macula.

The two pictures on the right show three months post micropulse laser, CME and leakage have completely resolved. Vision is 20/20. Note lack of any retinal damage or scar formation.

Comparison of Subvisible Micropulse Laser Efficacy in Treatment of Diabetic Macular Edema According to Initial Severity of DME 

The aim of this study is to answer the following:
Does the severity of diabetic macular edema have any effect on the effectiveness of micropulse laser treatment? If so, what is the optimal range of edema for maximal response?