Serial block face-scanning electron microscopy: a method to study retinal degenerative phenotypes

Retinal degenerative conditions can vary in their clinical features and often present with subtle phenotypic features before the onset of clinically overt disease. To capture these isolated events that precipitate disease, large representative areas of the retina must be imaged at high resolution. Compared to light microscopic methods, traditional electron microscopy can provide images at sufficient resolution to detect subtle pathologic changes in the retina, but are limited to the area being surveyed. The advent of serial block face-scanning electron microscopy (SBF-SEM) provides the resolution needed with the unprecedented advantage of imaging large volumes of retinal tissue. Furthermore, automation of SBF-SEM bypasses errors from manual sectioning and can produce reliable serial sections as thin as 25 nanometers. Moreover, the three-dimensional structures generated can highlight cellular connectivity and interactions in the retina and reveal pathological changes. Using SBF-SEM, we have identified subtle phenotypic features in mouse models of various human retinal dystrophies. This method will allow researchers to identify and monitor the time course of these pathologies. This article provides details on SBF-SEM methodology and its application to mouse models of retinal degeneration.