Circumscribed posterior keratoconus: case report

Posterior keratoconus has only a few scattered case reports in the literature. Posterior keratoconus is characterized by a posterior stroma thinning and a depression of the posterior corneal surface. The effect on acuity is variable and may be related to other ocular and systemic conditions.

An African-American woman came to us with posterior concavity (corneal thinning), with stromal scarring in both eyes and an epithelial iron ring present in the left eye. The endothelia layer appeared intact in both eyes. Corneal topography of the right eye demonstrated a central flattened zone with peripheral steepening, while the left eye an inferior nasal steepened zone was present. The patient was also diagnosed with myopic degeneration (O.D. > O.S.) as well as cataracts.

Posterior keratoconus generally has a minimal effect on visual performance and requires no specific treatment. In cases in which visual defect is severe and is attributable to the posterior keratoconus--and not other ocular conditions, such as cataracts--penetrating keratoplasty should be considered.