Examination of the angle of the anterior chamber of the human eye is shortened and simplified by the use of a contact prism which does not require unusual illuminating and microscopic equipment. The prism, which does not extend beyond the limbus, is placed directly on the cornea and is held in apposition with the cornea by pressure exerted through a flexible spring mounted on a speculum. A capillary film creates optical continuity between prism and cornea and, at the same time, lubricates the contact surfaces. Contacting surface A (fig. 1) conforms to the curvature of the anterior surface of the average cornea. Surfaces B and C form an internal reflecting prism. A ray of light from a in the angle of the anterior chamber is reflected at b to the observer, at c.
The prism is pivoted and suspended by fine wire springs, a (fig. 2A and B), from
ALLEN L, O'BRIEN CS. GONIOSCOPY SIMPLIFIED BY A CONTACT PRISM. Arch Ophthalmol. 1945;34(5):413–414. doi:10.1001/archopht.1945.00890190417012
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