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 1945,1 had 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 mirror2 was 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 (A, Fig. 1); a speculum (B), with a spherical flange (a) to
ALLEN L, BRALEY AE, THORPE HE. AN IMPROVED GONIOSCOPIC CONTACT PRISM. AMA Arch Ophthalmol. 1954;51(4):451-455. doi:10.1001/archopht.1954.00920040461004