Examination of contact lens surfaces by Atomic Force Microscope (AFM).

PURPOSE

We evaluated the use of Atomic Force Microscopy (AFM) in examining the surfaces of unused and worn hydrogel contact lenses under natural, fully hydrated conditions.

METHODS

Using the AFM contact mode, we examined hydrogel lenses (Acuvue, Surevue, NewVues, CSI Clarity, SeeQuence) that were hydrated.

RESULTS

Surface morphologies characteristics of each lens type and wear history were readily observed. The surfaces of worn lenses showed evidence of abrasion and altered morphology. These changes varied with type of contact lens and conditions of use and by site on the lens.

CONCLUSIONS

AFM is a very powerful tool for high resolution examination of hydrated contact lens surface structure. The method avoids artifacts due to dehydration and coating which can occur even with low voltage Scanning Electron Microscopy. Significant differences in contact lens surface morphology were observed before and after wear. These observations may be of importance in helping develop improved new lens polymers and ocular solutions.