Recurrence or re-emergence of keratoconus--what is the evidence telling us? Literature review and two case reports.

Keratoconus may recur following penetrating or lamellar keratoplasty, but latency is considerably longer in the former. Since keratoplasty involves only partial excision of the cornea, and recent research strongly indicates the presence of the pathology in the peripheral host cornea, the reappearance of the pathology after a latency period is most likely due to migration of the disease from host to donor cornea. This notion is further corroborated by the shorter latency period in partial thickness keratoplasty, where more of the diseased host cornea remains in place. Other proposed causes for the recurrence of keratoconus, such as eye rubbing and contact lens wear, were reportedly not associated with a significant number of cases, and, therefore, are not the primary factor. Based on existing literature, it is concluded that, in post-keratoplasty keratoconus, the etiology stems from re-emergence of the disease rather than recurrence. Keratoconus patients in need of keratoplasty should be counseled on the possibility of the disease re-emerging.