WHAT IS PHOTODYNAMIC THERAPY FOR VARICOSE VEINS?
Undoubtedly, laser is the most effective way to treat varicose veins. However, the Nd:YAG laser -the most widely used system for the treatment of varicose veins- only uses up to 30% of the emitted energy. To optimise the results of the treatment we need to improve the absorption coefficient of haemoglobin for wavelengths showing greater selectivity.
Instituto Médico Láser, in collaboration with the Laser and Beam Unit of the Multidisciplinary Institute of the Universidad Complutense de Madrid, has undertaken a research project that has made the above possible.
The technique consists in the combination of a laser with polydocanol. The presence of polydocanol foam increases the uptake of the laser energy up to 90%. This is due to an optical resonance phenomenon that takes place between haemoglobin and polydocanol. The combination of the laser with polydocanol constitutes what we have called Photodynamic therapy of varicose veins.
The studies of MiyakeRK and van Dam J demonstrated the conversion of haemoglobin into metahemoglobin and protoporphyrine IX in the presence of polydocanol.
Polydocanol is one of the most widely used agents in sclerotherapy of varicose veins, either in liquid form or in microfoam, and the only one authorised in Spain for this use. The injection of polydocanol causes an irritation of the venous endothelium with temporary stagnation of red cells. This irritation might or might not be followed by coagulation and fibrosis (the objective of chemical sclerotherapy). The injection of polydocanol also produces the conversion of haemoglobin into two derivates: metahemoglobin and protoporphyrine. Moreno Moraga J. and González Ureña A. have demonstrated that these metabolites have an absorption mechanism 4- times the absorption of haemoglobin for the elemental emission of the Nd:YAG laser at 1064nm.
On the other hand, according to Ebbesen TW and Hillembrand R, an extraordinary optical transmission caused by superficial tension phenomena occurs through submolecular pores. This means that photons emitted by a laser source are transmitted much more intensively if we have been successful in prompting the presence of these submolecular pores in the medium. These pores need to have a larger diameter than that of the wavelength of the laser used. Moreno-Moraga J and González-Ureña A have demonstrated that the optical transmission of the Nd:YAG laser in the presence of polydocanol foam, and due to this superficial tension effect, has a photonic transmission 29 higher than that obtained in normal blood.
In conclusion, this procedure is able to improve 4 times the uptake of the energy emitted by the Nd:YAG laser and improves 29 times the transmission of photons at 1064nm, which is the wavelength of the laser employed.