Purpose: To quantify potential relevant factors that affect the biocompatibility and functionality of intraocular lenses (IOLs) by analyzing the surface properties of various IOL materials.
Methods: Eleven IOL models with the same dioptric power made by different manufacturers were studied. The IOLs were made of poly-methyl methacrylate (PMMA), hydrophobic acrylate, hydrophilic acrylate, and silicone. The IOL surface topography was evaluated using atomic force microscopy (AFM). Surface potential was measured by electric force microscopy (EFM). Surface wettability was assessed with the water contact angle using the sessile drop method.
Results: The PMMA IOLs had statistically significant surface irregularities with the highest surface roughness values while the silicone and hydrophilic acrylic IOLs had the lowest values. Surface potentials on IOLs revealed that all IOL models made of PMMA had positive charge. The hydrophobic acrylic IOL had a significantly higher positive charge (6.2v ± 0.1v), while the hydrophobic acrylic with blue blocker exhibited negative charge. Negative charge was also observed on hydrophilic acrylic IOLs (-72mv ± 5mv) and silicone IOLs (-5.06v ± 0.02v). Contact angle values of PMMA IOLs ranged from 49° to 64°. Heparin modification resulted in significant reduction of the contact angle value. IOL models made of hydrophobic acrylate had contact angle values between 78° and 89°. The silicone IOL appeared to be significantly hydrophobic with the highest mean value of 107°.
Conclusions: The variance of the parameters of surface roughness, contact angle, and electrostatic charge on the surfaces of PMMA, hydrophobic acrylic, hydrophilic acrylic, and silicone IOLs is useful to the interpretation of the differences in clinical behaviors of these materials. The negative surface charge of silicone and hydrophilic IOLs might account for the occurrence of IOL calcification.
Keywords: Cataract; contact angle; intraocular lenses; surface potential; surface roughness.