Identification by Means of Low-Field Nuclear Magnetic Resonance of the Chemical-Physical Characteristics of Multidose Artificial Tear Solutions in Interaction with Hydrogel Model Contact Lenses

In this paper, the chemical-physical interactions between two commercially available ophthalmic solutions and hydrogel contact lenses classified according to the four Food and Drug Administration groups were studied by measuring transversal relaxation times (T₂) of water molecules by low-field nuclear magnetic resonance techniques. The aim was to evaluate possible modifications to the contact lens structure, with particular emphasis on their hydration mechanism. No significant variations in the T₂ values were observed when the T₂ values of the first component of samples swollen with saline solution as the reference were compared with samples of the same set of lenses swollen in the two commercially available ophthalmic solutions. We can, therefore, assume that the hydration characteristics remained unchanged in all the samples studied, and that the experimental ophthalmic solutions ensured an adequate hydration of the sample hydrogel contact lenses without any negative effects on the structure of their polymer chains.