The role of scanning electron microscopy in ophthalmic science.

The eyeglobe is one of the classical domains of Scanning Electron Microscopy (SEM) in biology as it exposes several inner and outer surfaces. Both corneal and conjunctival epithelia towards the tear film as well as the corneal endothelial cells facing the anterior chamber may be accurately evaluated. The architecture of the angle and particularly the morphology of the Schlemm's canal inner wall are clarified by SEM more than by TEM serial reconstruction. The surfaces of the iris and ciliary body, the zonula and the choroidal vessel arrangement are described in great detail. Three distinct types of membrane anchoring devices are demonstrated among the lens fibers. SEM impressively describes the retina, but it has not yet added any new information as to previous observations in a more conventional way. SEM plays a fundamental role in teaching ocular anatomy and physiology as it makes more comprehensive the interrelationships among different structures. In addition, it represents a proper structural approach of the clinician who is familiar with the three-dimensional observations obtained by means of biomicroscopy, ophthalmoscopy and fluorescein angiography. Therefore, SEM application should be further spread and possibly joined to immunocytochemistry, in order to obtain a more dynamic and functional analysis of the eye.