Photodynamic therapy (PDT): Sun Light as a therapy
What is photodynamic therapy or PDT? The use of sun light as a therapy has a long, long, history stretching back into antiquity. The rediscovery of phototherapy and its development in modern medicine was not until the second half of the 20th century when the ancient texts in German and French or Danish were translated for the English-speaking world.
Since then the phototoxic reactions, activated by the light on human tissues under specific conditions, have been used to treat several diseases including vitiligo, psoriasis and more recently cancerous and pre-cancerous lesions.
Photodynamic therapy (PDT) is a relatively young therapeutic modality that holds much promise for the treatment of illnesses characterized by the excessive proliferation of either host cells (i.e. neoplasms) or pathogens.
How it works?
The modern PDT is based on the local or systemic application of a photosensitive compound – the photosensitizer, which is accumulated in pathological tissues. These molecules absorb the light of the appropriate wavelength, initiating the activation processes leading to the selective destruction of the inappropriate cells. The photo-cytotoxic reactions occur only within the pathological tissues, in the area of photosensitizer distribution, enabling selective destruction. The main drawback of this procedure is the associated pain during the light (usually laser) treatment.
Natural Light PDT
Daylight PDT is a modified protocol of the standard treatment, which is more convenient and less painful as the daylight illumination leads to a significant reduction of aching. Unfortunately, daylight PDT is far less easy to control than the standard procedure. One of the main concerns is the measurement of the required light intensity to activate the therapeutic process.
Currently, there is no standardised or reliable method for light dosimetry during dPDT. It is therefore not possible to determine and influence the quantity of light a patient receives nevertheless some recent progresses in technology and home tele-medicine digital systems might soon offer a reliable method for light dosimetry during dPDT.