The Goldmann 3-mirror contact lens, as its name implies, incorporates 3 internal mirrors. The contact lens nullifies the refractive power of the cornea. The 3 mirrors then reflect light from the midperipheral retina, peripheral retina, and iridocorneal angle, respectively. The posterior pole of the fundus can also be visualized in a manner similar to that of a fundus contact lens.
http://creativecommons.org/licenses/by-sa/3.0/
