In 1999, a 64-year-old woman presented to the University of Rochester, Department of Ophthalmology, with diminished visual acuity, bilaterally. (A) Ocular examination showed widely dispersed straw-like interlacing deposits in the corneas of both eyes, strongly suggesting crystalline keratopathy. In this frontal view, the irregular dark areas represent more normal corneal light transmission in relatively unaffected areas centrally. Most of the cornea contains a network of apparent crystals forming an interlacing opacity. (B) Slit lamp examination showed the deposits were in the anterior corneal stroma resulting in an arc of opaque white coloration. The patient had no family history of corneal dystrophies. Crystalline keratopathy related to a crystal-forming monoclonal Ig was suspected. Indeed, she had a 0.5 g/dL serum monoclonal immunoglobulin, IgG-kappa, by zonal and immunoelectrophoresis. She has had no findings to indicate a progressive B-cell neoplasm during 16 years of follow-up. She had bilateral penetrating keratoplasty with restoration of visual acuity. (The authors thank Holly B. Hindman, M.D., University of Rochester, Department of Ophthalmology, for providing these images.)