Recent Advances in Corneal Imaging

The Structure of the Cornea

The cornea is a collection of cells and proteins that constitute a very highly organized structure. It is the clear outer layer, covering the front of the eye. The cornea must remain transparent to transmit and refract light. The cornea does not contain blood vessels to feed or protect it from infection, However it receives its nourishment from tears and the aqueous humour (fluid filling the Anterior chamber which is the space between the lens and cornea). Figure 1 shows the anatomy of the eye, and inspecting it we can recognize that the anterior surface of the cornea, which is not uniformly curved (H.E. Kaufman 2000; MedicineNet 2010).

Figure 1.

The anatomy of the Eye (MedicineNet 2010)

The dimensions of the cornea are, on average, 12.6 mm in the horizontal direction median and 11.7 mm in the vertical median. Its thickness is not uniform, with the central cornea thinner than the peripheral cornea (520 µm =< thickness <= 650 µm) (H.E.Kaufman 2000). The cornea has a tear film on its front surface and three main layers separated by two thin membranes. The Epithelial layer is the outermost layer of the cornea and is separated by the Bowman’s membrane from the central Stroma layer, which in turn is separated by the Descemet’s membrane from the innermost Endothelium layer as shown in Figure 2. Approximate thicknesses of these layers in the normal cornea are given in Table 1 (H.E. Kaufman 2000; Reinstein, Archer et al. 2008).

Figure 2.

The corneal layers