Limbus Corneae: An annular transitional zone, approximately 1 mm wide, between the cornea and the bulbar conjunctiva and sclera. It is highly vascular and is involved in the metabolism of the cornea. It is ophthalmologically significant in that it appears on the outer surface of the eyeball as a slight furrow, marking the line between the clear cornea and the sclera. (Dictionary of Visual Science, 3d ed)Vittaforma: A genus of parasitic FUNGI in the family Nosematidae that infects humans. Vittaforma corneae has been isolated from AIDS patients.Encephalitozoon: A genus of FUNGI originally considered a member of the class SPOROZOEA but now recognized as part of the class MICROSPOREA.Arcus Senilis: A corneal disease in which there is a deposition of phospholipid and cholesterol in the corneal stroma and anterior sclera.Microsporidia: A phylum of fungi comprising minute intracellular PARASITES with FUNGAL SPORES of unicellular origin. It has two classes: Rudimicrosporea and MICROSPOREA.Microsporidiosis: Infections with FUNGI of the phylum MICROSPORIDIA.Microsporida: An order of parasitic FUNGI found mostly in ARTHROPODS; FISHES; and in some VERTEBRATES including humans. It comprises two suborders: Pansporoblastina and APANSPOROBLASTINA.Epithelium, Corneal: Stratified squamous epithelium that covers the outer surface of the CORNEA. It is smooth and contains many free nerve endings.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)Conjunctiva: The mucous membrane that covers the posterior surface of the eyelids and the anterior pericorneal surface of the eyeball.Sclera: The white, opaque, fibrous, outer tunic of the eyeball, covering it entirely excepting the segment covered anteriorly by the cornea. It is essentially avascular but contains apertures for vessels, lymphatics, and nerves. It receives the tendons of insertion of the extraocular muscles and at the corneoscleral junction contains the canal of Schlemm. (From Cline et al., Dictionary of Visual Science, 4th ed)Corneal Diseases: Diseases of the cornea.Eye Burns: Injury to any part of the eye by extreme heat, chemical agents, or ultraviolet radiation.Corneal Transplantation: Partial or total replacement of the CORNEA from one human or animal to another.Burns, ChemicalCorneal Stroma: The lamellated connective tissue constituting the thickest layer of the cornea between the Bowman and Descemet membranes.Keratin-12: A type I keratin that is found associated with the KERATIN-3 in the CORNEA and is regarded as a marker for corneal-type epithelial differentiation. Mutations in the gene for keratin-12 have been associated with MEESMANN CORNEAL EPITHELIAL DYSTROPHY.Biological Dressings: Human or animal tissue used as temporary wound coverings.Corneal Neovascularization: New blood vessels originating from the corneal veins and extending from the limbus into the adjacent CORNEAL STROMA. Neovascularization in the superficial and/or deep corneal stroma is a sequel to numerous inflammatory diseases of the ocular anterior segment, such as TRACHOMA, viral interstitial KERATITIS, microbial KERATOCONJUNCTIVITIS, and the immune response elicited by CORNEAL TRANSPLANTATION.Stem Cells: Relatively undifferentiated cells that retain the ability to divide and proliferate throughout postnatal life to provide progenitor cells that can differentiate into specialized cells.Adenocarcinoma, Sebaceous: A malignant tumor composed of cells showing differentiation toward sebaceous epithelium. The tumor is solitary, firm, somewhat raised, more or less translucent, and covered with normal or slightly verrucose epidermis. It may be yellow or orange. The face and scalp are the commonest sites. The growth can be slow or rapid but metastasis is uncommon. Surgery cures most of the cases. (From Rook et al., Textbook of Dermatology, 4th ed, pp2403-4)Amnion: The innermost membranous sac that surrounds and protects the developing embryo which is bathed in the AMNIOTIC FLUID. Amnion cells are secretory EPITHELIAL CELLS and contribute to the amniotic fluid.Keratitis: Inflammation of the cornea.Fluorescent Antibody Technique, Indirect: A form of fluorescent antibody technique commonly used to detect serum antibodies and immune complexes in tissues and microorganisms in specimens from patients with infectious diseases. The technique involves formation of an antigen-antibody complex which is labeled with fluorescein-conjugated anti-immunoglobulin antibody. (From Bennington, Saunders Dictionary & Encyclopedia of Laboratory Medicine and Technology, 1984)Uvea: The pigmented vascular coat of the eyeball, consisting of the CHOROID; CILIARY BODY; and IRIS, which are continuous with each other. (Cline et al., Dictionary of Visual Science, 4th ed)Iris: The most anterior portion of the uveal layer, separating the anterior chamber from the posterior. It consists of two layers - the stroma and the pigmented epithelium. Color of the iris depends on the amount of melanin in the stroma on reflection from the pigmented epithelium.Stem Cell Niche: A particular zone of tissue composed of a specialized microenvironment where stem cells are retained in a undifferentiated, self-renewable state.Ophthalmologic Surgical Procedures: Surgery performed on the eye or any of its parts.Eye: The organ of sight constituting a pair of globular organs made up of a three-layered roughly spherical structure specialized for receiving and responding to light.Cochlea: The part of the inner ear (LABYRINTH) that is concerned with hearing. It forms the anterior part of the labyrinth, as a snail-like structure that is situated almost horizontally anterior to the VESTIBULAR LABYRINTH.Ciliary Body: A ring of tissue extending from the scleral spur to the ora serrata of the RETINA. It consists of the uveal portion and the epithelial portion. The ciliary muscle is in the uveal portion and the ciliary processes are in the epithelial portion.Eyelids: Each of the upper and lower folds of SKIN which cover the EYE when closed.Stria Vascularis: A layer of stratified EPITHELIUM forming the endolymphatic border of the cochlear duct at the lateral wall of the cochlea. Stria vascularis contains primarily three cell types (marginal, intermediate, and basal), and capillaries. The marginal cells directly facing the ENDOLYMPH are important in producing ion gradients and endochoclear potential.