Soft Contact Lens Surface Profile by Atomic Force Microscopy

AFM in mode Peak Force applied to the study of un-worn contact lenses

“…The Atomic Force Microscopy (AFM) is a technique that becomes useful to determine these properties, as was pointed out in an earlier work by Rabke et al [1]. Consequently, several authors [2][3][4][5][6][7][8][9][10][11][12][13][14][15] performed studies on CLs and using the AFM technique, but none of them used the Peak Force Quantitative Nanomechanics mode to determine the nanomechanical properties, such as the adhesion or the Young modulus, also named elastic modulus.…”

Hydrogel Contact Lenses Surface Roughness and Bacterial Adhesion

“…However, this is not the usual situation, as most of surfaces are not perfectly homogeneous in their irregularities distribution. In fact, there has been reported differences in CL surface roughness values at different magnifications using AFM technique, showing higher roughness scores in higher areas (Gonzalez-Meijome et al, 2006a;Giraldez et al, 2010c). Degree of variation of roughness parameters when increasing size of the measured area could be representative of how homogeneous a surface is.…”

“…In effect, AFM has proved useful for characterizing tear deposits on worn soft contact lens surfaces (Baguet et al, 1995;Rebeix et al, 2000) or characterizing the rigid gas permeable contact lens surface (Bruinsma et al, 2003). In fact, detailed information about the surface quality of CL has been studied previously by Atomic Force Microscopy (AFM) (Bhatia et al, 1997;Baguet et al, 1993;Baguet et al, 1995;Bruinsma et al, 2003;Gonzalez-Meijome et al, 2006a;Gonzalez-Meijome et al, 2009;Giraldez et al, 2010c) and Cryo-SEM (Gonzalez-Meijome et al, 2006b;Guryca et al, 2007). AFM is a very powerful tool for high resolution examination of hydrated CL surface structure.…”

“…The parameters generally used to quantify roughness include height parameters such as average roughness (Ra), mean-square-roughness (Rms) and Maximum Roughness (Rmax) (Baguet et al, 1993;Guryca et al, 2007;Bhatia et al, 1997;Hinojosa Rivera and Reyes Melo, 2001;Lira et al, 2008;Gonzalez-Meijome et al, 2009;Giraldez et al, 2010a;Giraldez et al, 2010c;Gonzalez-Meijome et al, 2006a). Ra is the average deviation or arithmetic mean of the profile from the mean line; it is universally accepted and is the most used international parameter of roughness.…”

“…(Giraldez et al, 2010c) Although the method used is the same as for dry conditions, a special cell could be necessary so measurements could be made on the lenses in their original shipping fluid (physiological saline) to keep CL hydrated during microscopy observation. All procedures and examinations must be conducted in the same room kept at 21ºC and approximately 50% relative humidity.…”