Studying functional properties of hydrogel and silicone-hydrogel contact lenses with PALS, MIR and Raman spectroscopy.Determination of free volume holes of the hydrogel and silicone-hydrogel polymer contact lenses were investigated.  Positron annihilation lifetime spectroscopy PALS was used to characterize geometrical sizes and fraction of the free volume holes in the investigated samples. 
PALS
Studying functional properties of hydrogel and silicone-hydrogel contact lenses with PALS, MIR and Raman spectroscopy.Determination of free volume holes of the hydrogel and silicone-hydrogel polymer contact lenses were investigated.  Apart from that, spectroscopic (middle infrared) MIR and Raman examinations were carried out in order to demonstrate the differences of the water content in the test contact lenses.
MIR
Studying functional properties of hydrogel and silicone-hydrogel contact lenses with PALS, MIR and Raman spectroscopy.Determination of free volume holes of the hydrogel and silicone-hydrogel polymer contact lenses were investigated. 
Raman spectroscopy