Scanning electron microscopy and energy dispersive spectroscopy findings in explanted PMMA and hydrophilic acrylic intraocular lenses.

PURPOSE To investigate the presence of calcium (Ca) aggregates influencing biocompatibility and the factors that affect calcium accumulation in explanted intraocular lenses (IOL) and to analyze the Ca distribution in an opacified hydrophilic acrylic lens. METHODS Surface irregularities and aggregates of 13 IOLs were studied with scanning electron microscopy, and their relative concentrations with energy dispersive spectroscopy (EDS). Relationships of distribution between Ca and silicone (Si) and nitrogen (N) and between N and Si and Na, and the influence of Si on Ca accumulation and the effect of differences in lens material on the distribution of N, and the effect of endophthalmitis on the distribution of Ca were evaluated statistically. EDS analyses were performed on the surface and cross-section of the opacified lens. RESULTS The statistically significant relationships between the distribution of Ca and N, and between the distribution of N and Na, the significant effect of Si on the Ca accumulation, significant relationship between endophthalmitis and the Ca accumulation in the aggregates were shown. The EDS analysis of the opacified IOL, Ca and P peaks were shown from the whole surface, Ca, O peaks were determined from cross-sections over a 70-80 mum distance. CONCLUSIONS In the aggregates influencing IOL biocompatibility, presence of proteins was determined to be more important than the presence of Si regarding the distribution of Ca, while the presence of Si affected the accumulation of Ca. Opacification, caused by the Ca accumulation within the lens, was found to result from Ca penetrating from lens pores.