An analysis of nodular deposits on soft contact lenses

Approximately 6.8 percent of soft contact lens wearers develop multiple nodular deposits on the front surface of their soft contact lenses. It was the purpose of this investigation to evaluate the role of calcium in the newly formed and mature deposits. Nodular deposits were examined using scanning electron microscopy and Energy Dispersive X-ray (EDX) analysis for calcium content. Any deposit which did not demonstrate the presence of calcium was sectioned, and the individual section re-examined by EDX analysis. Our results indicate that calcium was present in all but three of 72 nodular deposits investigated. The calcium was finely distributed throughout the deposits in a non-crystalline pattern, especially in the basal layers. Sections of the deposits also were examined at the light microscope level for the presence of lipids, calcium, and polysaccharides (mucin). All deposits stained positively for lipids, but polysaccharides were more evident in newer deposits. These results may indicate that both calcium and polysaccharides are involved in the genesis of nodular deposits.