Which layer of the cornea accounts for 90% of its thickness?

The stroma is the thickest layer of the cornea, making up about 90% of its total thickness. This layer consists primarily of collagen fibers arranged in a precise manner, which contributes to the cornea's transparency and structural integrity. The stroma's composition includes keratocytes, which are specialized cells that help maintain the corneal structure, and proteoglycans, which aid in the arrangement and spacing of collagen fibers.

The other layers of the cornea play vital roles, but they are much thinner in comparison. The epithelium serves as the outer protective layer, Bowman's layer acts as a tough barrier just beneath the epithelium, and Descemet's membrane is a thin layer that separates the stroma from the endothelium. While each of these layers is crucial for corneal function and health, the stroma is distinctly dominant in terms of thickness.