• Ocular surface

In the past, in vivo confocal microscopy (CM) was mainly used as a research tool to enable qualitative and quantitative study of the animal and human cornea in vivo.1–3 From the early 1990s onwards there has been a plethora of investigations of corneal structures describing findings both in healthy volunteers and in diseased patients. One of the main problems with most of these studies is their relatively low level of evidence; >80% of analysed papers published between 1990 and 2001 were classified by the American Academy of Ophthalmology's Ophthalmic Technology Assessment Committee Cornea Panel as case reports or case series.4

Nowadays, there are commercially available instruments that have quite clearly accomplished the step from ‘bench to bedside’, permitting microscopy of the entire ocular surface—that is, cornea, bulbar and palpebral conjunctiva, and lids. The axial resolution offered by competing types of confocal microscope (tandem scanning, 9 μm; slit scanning, 25 μm; laser scanning, 7–8 μm)5 affords an excellent opportunity to render tissue in three-dimensional (3D) proportions. Cell counts, 3D reconstruction,5 6 tracing of nerves7 and in vivo cell differentiation8 9 have resulted in an improved understanding of …