Comparison of Subthreshold 577 and 810 nm Micropulse Laser Effects on Heat-Shock Protein Activation Kinetics: Implications for Treatment Efficacy and Safety

Purpose: To compare the safety and efficacy of 810 versus 577 nm laser wavelengths for micropulse subthreshold (sublethal) laser treatment by mathematical analysis. Methods: Two different representative laser parameter sets for micropulsed subthreshold diode laser treatment, one employing 810 nm and the other 577 nm, are compared with regard to efficacy by analysis of the kinetics of laser-induced heat-shock protein (HSP) activation; and for safety, by scaling law analysis. Results: Kinetics analysis of laser-induced HSP activation shows that the primary therapeutic effect of laser is thermal incitement of a long-term wavelength-independent increase in the rate of HSP-mediated protein repair specific to sick and dysfunctional cells, rather than from short-term increases in free intracellular HSP concentrations. Scaling law analysis of the same 810 and 577 nm laser parameters, however, finds treatment safety highly wavelength-sensitive, favoring 810 over 577 nm. Conclusions: Mathematical analyses of the effects retinal laser-induced HSP activation provide important insights into the mechanism of action and the importance of wavelength selection in modern retinal laser therapy. Our analyses find 810 and 577 nm to be equally effective, but 810 nm having a significantly wider therapeutic range/safety margin, and thus less likely to cause inadvertent, and thus unpredictable, laser-induced retinal damage, than 577 nm. Translational Relevance: Mathematical analysis of enzyme reaction kinetics provides important insights into the mechanism of action and clinical implications of wavelength selection in modern retinal laser therapy.