Among the rare forms of corneal abnormalities, there exists a group characterized by anomalies of curvature of the posterior corneal surface. Butler has named and described two types of abnormal posterior corneal curvature. One form is called keratoconus posticus and is characterized by a perfectly regular and unusually short radius of curvature for the entire posterior corneal surface. The other form, called keratoconus posticus circumscriptus, shows a localized area of increased curvature on the posterior corneal surface. In both types the anterior corneal curvature is smooth, regular and of average radius. In both types the cornea is thinned in the area of increased curvature. This thinning involves the entire cornea in the first, or keratoconus posticus, type and is limited to a circumscribed area in the second type.1
Stallard,2 in 1930, reported the first case of so-called keratoconus posticus circumscriptus. Butler2b and Ingram3 each recorded a
LEOPOLD IH. KERATOCONUS POSTICUS CIRCUMSCRIPTUS. Arch Ophthalmol. 1943;30(6):732–734. doi:10.1001/archopht.1943.00880240046004
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