Descemet Stripping Endothelial Keratoplasty: A surgical procedure or KERATOPLASTY involving selective stripping and replacement of diseased host DESCEMET MEMBRANE and CORNEAL ENDOTHELIUM with a suitable and healthy donor posterior lamella. The advantage to this procedure is that the normal corneal surface of the recipient is retained, thereby avoiding corneal surface incisions and sutures.Keratoplasty, Penetrating: Partial or total replacement of all layers of a central portion of the cornea.Descemet Membrane: A layer of the cornea. It is the basal lamina of the CORNEAL ENDOTHELIUM (from which it is secreted) separating it from the CORNEAL STROMA. It is a homogeneous structure composed of fine collagenous filaments, and slowly increases in thickness with age.Fuchs' Endothelial Dystrophy: Disorder caused by loss of endothelium of the central cornea. It is characterized by hyaline endothelial outgrowths on Descemet's membrane, epithelial blisters, reduced vision, and pain.Corneal Edema: An excessive amount of fluid in the cornea due to damage of the epithelium or endothelium causing decreased visual acuity.Corneal Endothelial Cell Loss: Loss of CORNEAL ENDOTHELIUM usually following intraocular surgery (e.g., cataract surgery) or due to FUCHS' ENDOTHELIAL DYSTROPHY; ANGLE-CLOSURE GLAUCOMA; IRITIS; or aging.Endothelium, Corneal: Single layer of large flattened cells covering the surface of the cornea.Corneal Transplantation: Partial or total replacement of the CORNEA from one human or animal to another.Corneal Diseases: Diseases of the cornea.Eye Banks: Centers for storing various parts of the eye for future use.Pseudophakia: Presence of an intraocular lens after cataract extraction.Corneal Stroma: The lamellated connective tissue constituting the thickest layer of the cornea between the Bowman and Descemet membranes.Visual Acuity: Clarity or sharpness of OCULAR VISION or the ability of the eye to see fine details. Visual acuity depends on the functions of RETINA, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast.Cornea: The transparent anterior portion of the fibrous coat of the eye consisting of five layers: stratified squamous CORNEAL EPITHELIUM; BOWMAN MEMBRANE; CORNEAL STROMA; DESCEMET MEMBRANE; and mesenchymal CORNEAL ENDOTHELIUM. It serves as the first refracting medium of the eye. It is structurally continuous with the SCLERA, avascular, receiving its nourishment by permeation through spaces between the lamellae, and is innervated by the ophthalmic division of the TRIGEMINAL NERVE via the ciliary nerves and those of the surrounding conjunctiva which together form plexuses. (Cline et al., Dictionary of Visual Science, 4th ed)Keratoconus: A noninflammatory, usually bilateral protrusion of the cornea, the apex being displaced downward and nasally. It occurs most commonly in females at about puberty. The cause is unknown but hereditary factors may play a role. The -conus refers to the cone shape of the corneal protrusion. (From Dorland, 27th ed)Corneal Surgery, Laser: Surgical techniques on the CORNEA employing LASERS, especially for reshaping the CORNEA to correct REFRACTIVE ERRORS.Corneal Wavefront Aberration: Asymmetries in the topography and refractive index of the corneal surface that affect visual acuity.Lasers, Excimer: Gas lasers with excited dimers (i.e., excimers) as the active medium. The most commonly used are rare gas monohalides (e.g., argon fluoride, xenon chloride). Their principal emission wavelengths are in the ultraviolet range and depend on the monohalide used (e.g., 193 nm for ArF, 308 nm for Xe Cl). These lasers are operated in pulsed and Q-switched modes and used in photoablative decomposition involving actual removal of tissue. (UMDNS, 2005)Refraction, Ocular: Refraction of LIGHT effected by the media of the EYE.Tissue Donors: Individuals supplying living tissue, organs, cells, blood or blood components for transfer or transplantation to histocompatible recipients.Lens Implantation, Intraocular: Insertion of an artificial lens to replace the natural CRYSTALLINE LENS after CATARACT EXTRACTION or to supplement the natural lens which is left in place.Corneal Opacity: Disorder occurring in the central or peripheral area of the cornea. The usual degree of transparency becomes relatively opaque.Graft Survival: The survival of a graft in a host, the factors responsible for the survival and the changes occurring within the graft during growth in the host.