LF-NMR water self-diffusion and relaxation time measurements of hydrogel contact lenses interacting with artificial tears.

The different swelling properties of ionic and non-ionic lenses, immersed in sodium chloride or artificial tears, were investigated by Low-Field Nuclear Magnetic Resonance (LF-NMR) through relaxation time and self-diffusion coefficient measurements. A new model was developed to estimate the water self-diffusion coefficient inside the lenses, the results of which revealed a different mechanism of interaction for ionic versus non-ionic materials with artificial tears. The consequence of this finding suggests clinical implications.