Evidence for posterior zonular fiber attachment on the anterior hyaloid membrane.

PURPOSE To image the posterior zonular attachment site by using environmental scanning electron microscopy (ESEM). METHODS A custom-made device was designed to mount human cadaveric lenses, with the zonule, ciliary body, and sclera attached, inside an environmental scanning electron microscope (ESEM). The mount was designed to allow radial stretching to enhance exposure of the accommodation apparatus. Seven fresh human eye bank eyes (age: 62-82 years; 24-48 hours after death) were dissected, mounted, and imaged in wet mode. The insertion site of the posterior zonule was examined. RESULTS Detailed pictures of the accommodation apparatus were obtained in all eyes. A strong relation between the posterior zonule and the anterior hyaloid membrane was observed. Anterior view micrographs showed that posterior zonular fibers originate from the ciliary body and anchor in the hyaloid membrane. From the point of insertion, the fibers continue on their course toward the posterior lens capsule in the plane of the hyaloid membrane. CONCLUSIONS Contrary to the classic description, the majority of posterior zonular fibers are not attached directly to the posterior lens capsule, but are anchored to the anterior hyaloid membrane on their path from the ciliary body to the posterior capsule. This finding is in good agreement with several previous observations and models that suggest support of the posterior lens surface during accommodation.