Scleral ectasia secondary to Acanthamoeba keratitis.

An unrecognized case of Acanthamoeba keratitis became quiescent after prolonged scleritis, resulting in a central corneal scar with extensive scleral ectasia. Twenty-one months after the onset of the sclerokeratitis, a penetrating keratoplasty was performed. Acanthamoeba cysts were found in the host corneal button. The corneal transplant has remained thin and clear for 2 1/2 years following surgery. Acanthamoeba keratitis extending to the limbus may become self-limited due to immunologic mechanisms available at the limbus, which do not appear to be active within the cornea itself. However, the prolonged inflammatory reaction manifesting as scleritis may result in extensive scleral ectasia.