Keratoconus Experimentally Produced in the Rat by Vitamin a Deficiency.

KERATOCONUS is comparatively speaking a rare disease, but as a clinical entity it has been known for many years. Its aetiology is, however, still obscure, and its treatment is unfortunately one of the failures of ophthalmology. It has been thought that it might be a deficiency disease, and recent attempts to cure the condition by administration of vitamin D and calcium have been made. (Knapp, 1938.) Cantor (1927) observed that there was an alteration in the shape of the cornea with the production of myopia and astigmatism in patients suffering from chronic keratomalacia. As it is now an established fact that keratomalacia or xerophthalmia is due to avitaminosis A, it is surprising that so little has been done to establish some connection between keratomalacia and keratoconus. Gudjonsson (1930) mentions that .keratoconus was in his experiments a frequent sequel to xerophthalmia in rats on a vitamin A-free diet. In the detailed description which he gives, however, keratoconus is not described but illustrations are given of what is called buphthalmos. No other detailed description of either conditign can be found in the literature. a In a recent experiment at the Rowett Institute, certain rats which had been kept since weaning on a vitamin A-free diet until clinical symptoms of avitaminosis A were noted, were subsequently given a large daily dose of the vitamin. After some days it was observed that several of the rats were suffering from acute keratoconus. One rat showed distinct keratoconus before vitamin A dosage was begun. It was then decided to conduct a fresh experiment with the object of producing keratoconus in the rat, in order that the condition might be more closely studied.