Corneal Degenerations and Ectasias

Degeneration of a tissue is defined as a deterioration that results in impaired structure and function. These changes occur at the cellular level and are caused by biomolecular alterations induced by aging, as well as a wide variety of adverse external and internal influences. Traditionally, degenerations have been classified as involutional (age-related) or non-involutional, depending on type of deposition (hyaline, amyloid, lipid, calcific), and by anatomic location (anterior, posterior, central or peripheral). Degenerations may be unilateral or bilateral, often with asymmetric involvement. Heredity does not play a direct role in these processes. The noninflammatory ectatic diseases of the cornea discussed in this chapter include keratoconus, pellucid marginal degeneration, keratoglobus, and posterior keratoconus. An exceptional degeneration unreported in literature (presumed alimentary cuprum keratopathy) is presented in this chapter. Pseudogerontoxon is one of the characteristic degenerations commonly seen in Middle Eastern populations.