The Hruby-lens--used inverse (author's transl)]

The Hruby-lens may be used as a contact lens with the plano surface in contact with the cornea and the concavity facing the microscope. The observer surveys a large field of the fundus. By decentering the lens, adjacent and peripheral areas of the fundus are drawn into the observer's field. This increases further the total area of fundus that can be observed.