Hydroxyapatite formation on implanted hydrogel intraocular lenses.

Three Chinese patients undergoing implantation with the same hydrogel intraocular lens (IOL)(Hydroview; Bausch & Lomb Surgical, Claremont, Calif) developed delayed IOL opacification with unusual clinical features. The IOLs were made from a 2-hydroxyethylmethacrylate/6-hydroxyhexylmethacrylate (HEMA/HOHEXMA) copolymer. Opacification was progressive, whitish, and generalized, and developed 4 to 15 months after surgery. The appearance resembled a mature cataract. All 3 patients showed a significant reduction in vision. There was no response to Nd:YAG laser treatment, and all 3 IOLs had to be explanted. The explanted lenses were analyzed with electron microscopy, elemental analysis, Fourier Transform (FT) Raman spectroscopy, and x-ray diffraction to define the nature of the opaque material. Results showed electrondense deposits in the superficial 5 μm of the lenses. The deposits were predominantly composed of calcium and phosphorus, and x-ray diffraction identified the presence of hydroxyapatite. The polymer structure of the lens was unaltered.