Knowing the importance of stroma(90%) in function and anatomy of corneae (transparence, curvature, strength, protection) the inner eye structures from external environment, we have examined the role and function of stroma as a main factor of corneal thickness in implanting fresh corneal lenticule in progressive corneal disease.~We have studied that in many clinical cases where the corneal epithelium and endothelium are healthy and functioning, the cornea can still lose it's transparency by different corneal stromal pathologies (infection ,keratoconus, inflammation ,neurodegeneration and corneal dystrophies).
Stroma is a fibrous, tough, transparent and the thickest layer of the corneae. The stroma is composed of organised collagen, which maintains transparency. Keratocytes are located between the lamella collagen fibers and secrete an extracellular matrix, which includes collagen, proteoglycan, crystalline proteins to maintain corneal transparency.