High resolution scanning electron microscopy of the retinal pigment epithelium and Bruch's layer

The application of a new technique in vision research for investigating the three-dimensional ultrastructure of extra- and intracellular organelles and components is presented, based on the use of high resolution scanning electron microscopy (HRSEM). This technique has been made possible by advances in scanning electron microscope design which permit resolution of particles less than 3 nm in diameter and new tissue preparation techniques which remove the cytosol and leave cell membranes and organelles in relief. Application of these methods to the ultrastructure of the retinal pigment epithelium and Bruch's layer in the albino rat has revealed a number of new structural features and confirmed others by using a different approach in tissue preparation and examination. It is now possible to obtain HRSEM micrographs with an information content equivalent to at least 15 ultrathin, serial, transmission electron microscope sections, all perfectly aligned, in one micrograph without having to resort to accepted reconstruction techniques. It is clear that this new method has the potential to rapidly advance our knowledge of the structures involved in vision in both health and disease and in a variety of experimental conditions.