Rigid gas permeable contact lenses surface roughness examined by interferential shifting phase and scanning electron...

The anterior surface roughness of seven factory new rigid gas permeable (RGP) contact lenses has been studied by interferential shifting phase microscopy (ISPM) and scanning electron microscopy (SEM). Five lenses were fluorsilicone acrylate and two lenses were silicone acrylate. Their material Dk ranged from 14 to 210. ISPM is shown to be a reliable and non-destructive method to observe and measure the relief of the contact lens surface. Moreover, profile and contour data are easily stored for further quantitative studies. ISPM contour patterns of the studied lenses are qualitatively compared with those obtained by SEM for the same lenses. Results point out that ISPM gives similar accuracy but it is non-destructive and cheaper than SEM. Moreover, the quantitative study of surface roughness suggests that there is a relationship between surface roughness and Dk of the lens material: surface roughness increases with Dk and allows to distinguish between lenses with low, medium and high Dk.