Secondary Keratoconus with Corneal Epithelial Iron Ring Similar to Fleischer's Ring

Background: Fleischer's ring is considered to be a characteristic of keratoconus, but we have seen a ring similar to Fleischer's ring in patients with secondary keratoconus, in which the cornea becomes thinner secondarily for undetermined reasons. Cases: We report 6 cases of secondary karatoconus with a corneal epithelial ring similar to the Fleischer's ring pattern. Observations: In these 6 cases (2 men and 4 women), the causes of secondary keratoconus were trachoma in 2 cases, trauma in 2 cases, keratitis in 1 case and unknown etiology in one case. All showed thinning of the cornea and a corneal iron ring similar to Fleischer's ring pattern. The corneal button obtained after keratoplasty in 1 case showed the deposition of hemosiderin in the corneal epithelium after staining with Prussian blue. At the same time we confirmed the existence of iron in the corneal epithelium by x-ray ultimate analysis. Conclusions: All 6 patients we encountered had a past history of corneal disease in their childhood except for 1 case with unknown etiology. Primary keratoconus is also considered to develop by the early teens at the latest. These facts led us to an assumption that the occurrence of some abnormalities in the cornea during the growth period may result in iron deposition in the epithelium and thinning of the stroma. In light of these facts, abnormalities of the iron metabolism must be thoroughly investigated in considering the etiology of keratoconus.