Stroma collagen lamellae

Figure 3.4. Structure of cornea. The structural components of cornea include epithelium, corneal stroma, collagen lamellae and Bowman s and Descemet s membranes.

The Stroma, or substantia propria, is composed of around 90% of the corneal thickness that contains about 85% water and about 200-250 collagenous lamellae. The lamellae provide physical strength while permitting optical transparency of the membrane. The hydrophilic solutes diffuse through the stroma s open structure. 

O. Damour, et al.. Orthogonal scaffold of magnetically aligned collagen lamellae for corneal stroma reconstmetion, Biomaterials 28 (2007) 4268-4276. 

The outer surface of the cornea is covered with a smooth layer of stratified corneal epithelium (Figure 3.4). The lower layer of cells is columnar in shape and rests on a basement membrane that sits on top of a thick limiting structure termed Bowman s membrane derived from the corneal stroma below. The corneal stroma is composed of parallel bundles of collagen fibrils termed lamellae and rows or layers of branching corneal fibroblasts termed keratocytes. The posterior of the cornea is covered with a low cuboidal epithelium with a wide basement membrane (Descemet s membrane) and rests on the posterior portion of the corneal stroma. The corneal epithelium is normally under tension due to the pressure that is present in the anterior chamber just behind the cornea. The intraocular pressure is between 10 and 20 mm of mercury and is enough to cause the cornea to contract about 5% when it is excised from the eye. Therefore this pressure must be transferred between epithelium via cell-cell junctions. 

---