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The authors give the history of the contact lens from the time it was first used by J. H. Herschell, in 1827, to protect the globe from palpebral disease and its application by Fick, of Zurich, in 1888, in cases of keratoconus and ametropia, to the introduction of the molding procedure and of the plastic contact lens, which were developed chiefly by Obrig.
The contact lens can be used for gonioscopy ; for the correction of ametropias, especially in cases of optical keratoconus ; for the correction of astigmatism after corneal transplantation; in cases of monocular aphakia, and for protection of the globe in cases of trichiasis, distichiasis, lagophthalmos and entropion.
In its application, it is necessary to know the radius of curvature of the anterior 5 mm. of the sclera, which fluctuates from 10 to 15 mm., and the diameter and radius of curvature of the cornea. Measurements obtained by molding