Laser Resensitization of Medically Unresponsive Neovascular Age-Related Macular Degeneration

Abstract

Subthreshold diode micropulse laser treatment restored drug response in drug-tolerant eyes with neovascular age-related macular degeneration. Based on these findings, a theory of SDM action is proposed, suggesting a wider role for SDM as retinal reparative/protective therapy.

Subthreshold diode micropulse laser versus observation in acute central serous chorioretinopathy

“…SDM laser causes resolution of CSC by normalisation of retinal pigment epithelium function and retinal autoregulation by means of sublethal retinal pigment epithelium heat‐shock protein activation (reset to default theory) or possibly by causing cytokine expression which decreases choroidal hyperpermeability.…”

Comparison of Continuous-Wave and Micropulse Modulation in Retinal Laser Therapy

“…NRT is believed to work by triggering a cellular response to sublethal thermal stress in the retinal pigment epithelium (RPE) and possibly other layers, which helps to restore normal function to diseased tissue. 4,5 The major challenge of this approach is the proper calibration of laser parameters to deliver a sufficient amount of thermal stress to induce therapeutic effect without excessive heating, which can kill RPE cells, overlying neural retina, or underlying choroid. This calibration is complicated by patient-to-patient and spot-to-spot variations in pigmentation and ocular transparency, which define the fraction of laser power being converted into heat.…”

“…Clinical studies utilize a wide range of treatment parameters, with duty cycles (ratio of the laser micropulse duration to its period, 2 ms) ranging from 5% to 15%, total pulse lengths from 20 to 300 ms, and disparate titration procedures producing inconsistent outcomes, [11][12][13] which are difficult to compare to one another or to continuous-wave (CW) laser. In several studies, titration is neglected altogether, and a single parameter set is used for all patients, 5,14 assuming that a sufficiently wide therapeutic window is enabled by the micropulse laser.…”

Subthreshold Diode Micropulse Laser: A Review

“…Heat shock proteins are ubiquitous molecules which are produced in response to stress and help repair damaged tissue and create ''thermotolerance,'' increasing the threshold at which cell damage and apoptosis occur from thermal, inflammatory, oxidative, or hypoxic injury. 18,19 Sramek et al have shown that the energy required to stimulate heat shock protein expression is significantly lower than the energy required to cause apoptosis or a visible laser burn. 18 An effective subvisible laser relies on the proper titration of laser parameters to achieve energy levels that are high enough to ''stress'' the RPE cells and produce a biochemical response without causing permanent cell damage.…”

“…19 Thirteen patients were included who showed persistent leakage on FA or fluid on OCT after multiple monthly anti-VEGF injections, including a failed trial of three monthly aflibercept injections. They were treated with subthreshold micropulse laser before resuming aflibercept injections.…”