[Alterations of heparin coating on intraocular lenses caused by implantation instruments]

In the last years heparin surface-modified intraocular lenses (HSM IOLs) were used for special indications like uveitis, synechia, congenital cataract or pseudoexfoliation syndrome. A monolayer of heparin molecules on the surface of PMMA-IOLs causes a reduced postoperative inflammatory reaction and produces a higher long-term biocompatibility than PMMA-IOLs without surface-modification. The study was designed to evaluate the possible damage of this heparin-monolayer on the PMMA-IOL by different metallic implantation forceps and different grasp-pressure.

Different implantation instruments were used to grasp HSM and conventional PMMA-IOLS. We designed a new device to generate and measure the pressure by the implantation forceps on the IOL in online-mode. After staining the heparin-monolayer with toluidin blue the surface alterations on the intraocular lenses were examined for surface alterations, especially of the heparin-monolayer, by light and scanning electron microscopy subsequently.

Implant forceps produced defects of the heparin layer and the PMMA-material. Each implantation forceps induced a specific pattern of destructed heparin surface in the grasp area. These defects showed high correlation with the pressure and the morphology of the forceps as shown by light and scanning electron microscopy.

Mechanical irritation during the implantation procedure destroyed the heparin layer on PMMA-IOLs in the grasp-area. Clinical consequences are not yet known, but possible. An instrument with rounded, soft and smooth grasp-surface is required for implantation of HSM IOLs to avoid surface alterations, so that the patients get maximum profit by the heparin-modification.