The margin of the cornea is in relation with three membranes, the conjunctiva, the sclera and the uvea (iris and ciliary body). In a disease of the cornea, a conjunctivitis, an iritis or a cyclitis is easily started. The cornea contains no vessels. It is nourished by imbibition. At the limbus there is a rich network of marginal loops supplied by the anterior ciliary vessels. From these loops the blood plasma passes into the stroma of the cornea. The nerves of the cornea come from the ciliary nerves and the nerves of the bulbar conjunctiva. These are from the trigeminus and the sympathetic. The nerves extend numerously in the stroma passing forward through Bowman’s membrane into the epithelial layer. This makes the cornea very sensitive to the touch. Examination of the Cornea Note the size and form. Both may be modified by morbid processes. Note the surface with regard to curvature, evenness and smoothness. In =keratoconus= the curvature is greatly increased. Noting the reflex images in the cornea and comparing these with those of a normal cornea will show any variation in curvature. Also any =unevenness of the surface= may be noted by the irregularity or distortion of the images. Uneven spots on the cornea may be =depressions or elevations= from loss of substance; =wrinkles or collapse= from lowered tension. If the smoothness or polish of the cornea is lost it looks like glass that has been breathed upon or greased. It is lusterless and dull. Note also the transparency of the cornea and determine the form, extent and density of the opacity; whether it is diffuse or in spots; in the deep or superficial layers. A magnifying glass should be used in the study of opacities. According to the density of the opacity of the cornea it is known as a =nebula= or a =nebulous opacity=, a =macula= or a =leucoma.= The nebula is the least noticeable and the leucoma is the densest opacity. A leucoma is a condition of complete opacity. The cornea looks white. Defects in the corneal epithelium may be made to show clearly by the use of a 2% solution of fluorescein which stains them green. Note the sensitiveness of the cornea by touching it with the end of a thread, a little cotton or a shred of paper. The sensitiveness is diminished or lost in glaucoma and some other diseases. Diseases of the Cornea Almost all diseases of the cornea have some form or degree of inflammation. =Keratitis= is the word generally used for inflammation of the cornea. In order to aid clearness in discussion there are various subdivisions of keratitis made by different writers. Suppurative and non-suppurative are the principal types. In =suppurative keratitis= there is always some destruction of corneal tissue which on healing leaves an opacity with partial loss of vision. Germs gain entrance into the tissues usually from the exterior and some form of ulceration results. The following classification is taken from Fuchs: