Because of the weak penetration of light, Photodynamic Therapy was used mostly to treat tumors located in human skins, but not those in deeper part of human bodies.

And as you watched the light on that river, somehow you seemed to lose yourself, and as you closed your eyes there was a penetration into a void that was full of blessing.

Single PVC layer be improved by special technologies and suface treatment can reduce the reflection of the light, which means the rate of light penetration can be increased.