With conventional (classic) laser, the treatment endpoint is a readily visible burn. This implies a high and lethal thermal gradient (>30 ºC) in the tissue directly targeted by the laser, as well as in the adjacent tissue reached by the equilibrating and decaying thermal wave at a still lethal temperature. The enlarged burn becomes visible some time after treatment and progresses in an atrophic scar, which expands over time. Surrounding tissue reached by the equilibrating and decaying thermal wave at a sublethal temperature, remains viable and capable of reacting to the thermal injury with stress responses which induce beneficial intracellular biological factors that are antiangiogenic and restorative.1
With modified (classic) laser, the lighter treatment endpoint of a barely visible burn is sought. Directly targeted tissue is still destroyed, with scar enlarging and expanding over time, but the effects, although similar as with conventional laser, are confined to a smaller region surrounding each burn.
With MicroPulse Laser Therapy (MPLT), the temperature rise induced in the directly targeted tissue remains sublethal and no visible lesion is produced (subvisible-threshold). Because of this, both directly targeted and surrounding tissues remain viable and capable of creating a stress response which induces beneficial intracellular biological factors that are antiangiogenic and restorative.
In MPLT, the low temperature gradient reequilibrates to baseline temperature within a short spreading distance, limiting and confining the therapeutic photothermal effect around the tissue directly targeted by the laser. For this reason, and conversely to conventional (classic) laser that must be applied in grids with spaced burns, MPLT is normally performed with the high-density placement of confluent applications, a novel laser treatment paradigm that is made possible by the absence of chorioretinal laser damage and risk of iatrogenic scotoma.
- Mainster MA. Laser-tissue interactions: future laser therapies. Invited lecture ARVO/NEI 2010 Summer Eye Research Conference, NIH, Bethesda, MD; 2010.