A review of Subthreshold Micropulse Laser for Treatment of Macular Disorders
Adv Ther. 2017;34(7):1528-1555.
Very interesting meta-analysis of published literature of subthreshold micropulse laser treatment for Central Serous Retinopathy, Retinal Vein Occlusion and Diabetic Maculopathy.
Micropulse laser is a new laser treatment modality which is different from conventional continuous wave retinal laser treatments. It delivers laser treatment to the fovea without causing retinal damage.
The laser energy stimulates the retinal pigment epithelium (the supporting cells of the light sensitive photoreceptors), which leads to repair of the inner blood retinal barrier. A modification of the gene expression initiated by the wound healing response after laser photocoagulation could be responsible for its beneficial effect.
The laser is delivered in pulses lasting microseconds compared to previous milliseconds. The interval between pulses is very important as the cell needs to have time to cool down between shots to avoid cellular damage.
It is a very exciting modality particularly in Diabetic maculopathy as the present standard treatment of this condition has moved from previous conventional laser to intravitreal VEGF or steroid treatment. A return to laser with micropulse may avoid the need for injections which I am sure our patients would prefer. However as this article reveals there is much work needed in researching the optimal laser setting to achieve the maximum therapeutic effect. Most of the reviewed papers differed quite significantly in the laser settings used. Despite this micropulse laser showed an average gain of 1.26 letter over conventional laser which showed a 0.29 reduction in vision on average. The response ranged between a reduction in 6 letters to 19 letter gain. A 19 letter gain would be very comparable to the intavitreal injections.
Central Serous retinopathy fared well with an average reduction of 131 micrometres in central macular thickness with an average of 6.34 letter gain. This compares well against standard Photodynamic therapy which has a 85 micrometres average reduction in central macular thickness and 3.87 letter gain.
Branch Retinal Vein occlusion showed an average of 122 micrometres reduction in central macular thickness and a 2.98 letter gain.
It is clear that micropluse laser has a therapeutic effect. It is likely to be temporary and further repeat micropulse laser treatment would be needed. A combination treatment perhaps starting with an intravitreal injection followed by micropulse laser may enhance its benefit when the retina thickness is reduced and an optimal standard laser setting could be deployed to give the desired effect.
Other indication for this treatment might include a possible new treatments for normotensive glaucoma and genetic retinal dystrophies. It has been used in vitrectomy surgery to treat such conditions such as optic disc pits without doing damage to the nerve.
Investing in micropluse laser capability in any future laser purchases within our Irish hospitals makes good sense.