AN IMPROVED GONIOSCOPIC CONTACT PRISM

Abstract

THE GONIOSCOPIC contact prism shown in Figure 1 incorporates four internal reflecting surfaces to facilitate examination of the angle of the anterior chamber of the eye. Such an improvement over the original prism, described in 1945,¹had been attempted before the first publication, but the speculum could not retain the heavy prism against the cornea. A subsequent change in the design of the speculum would have overcome this difficulty, but advantage was not taken of this opportunity until 1951, when a second mirror²was added in a successful modification of the original design. Thorpe's instrument required fewer manipulations and thus shortened and simplified the examination. The instrument described here is a further step in the same direction, made possible by redesigning several of the mechanical features of the device. The new instrument consists of the prism (<i>A</i>, Fig. 1); a speculum (<i>B</i>), with a spherical flange (<i>a</i>) to