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Keywords:

  • bathochromic shift;
  • blood coagulation;
  • laser therapy;
  • methemoglobin;
  • port wine stain;
  • purpura;
  • selective photothermolysis

Abstract

Background and Objectives

Two wavelengths, 585 and 595 nm, are currently common options for treating vascular malformations such as port-wine stains (PWS). Controversy exists as to which wavelength induces greater photothermal damage to the blood vessels and subsequent resolution of the malformations.

Study Design/Materials and Methods

We irradiated normal, human skin in vivo at 585 and 595 nm wavelengths using fluences of 10–30 J/cm2 with a 1.5 millisecond laser pulse. The level of purpura, total vascular damage, maximum coagulation depth (MCD), and perivascular damage were quantified by gross observation and histological analysis.

Results

Results demonstrated that 585 nm light caused greater purpura, vascular damage, maximum coagulation depth, and perivascular damage than 595 nm. Purpura showed a positive correlation with total vascular damage to a certain extent beyond which the total vascular damage did not change. For equivalent purpura, 585 and 595 nm produced no statistically significant difference in vascular damage. The difference in the laser-induced vascular damage between 585 and 595 nm, although statistically significant, was no more than 50%.

Conclusions

The bathochromic (red) shift and formation of met-hemoglobin, which reduces the 585 nm light absorption and increases that of 595 nm compared to native oxy-hemoglobin, play a considerable role in creating more parity in vascular damage between the two wavelengths than would be expected based on their respective “native” absorption coefficients alone. Lasers Surg. Med. 36:117–123, 2005. © 2005 Wiley-Liss, Inc.