Excerpt from The Practical Medicine Series, Vol. 3: Comprising Right Volumes on the Year's Progress in Medicine and Surgery, The Eye, Ear, Nose and ThroatTests for Visual Acuity. For the subjective testing of refraction, Edward J ackson1 believes that the inter national broken ring test is inferior to the test letters, but for testing acuteness of vision, it is distinctly bet ter. When, however, the broken ring is arranged like test letters in successive lines of varying sizes, it has no advantage over the test letters, and some disadvantages. It is when a single size of broken ring is arranged in a symmetrical card that its advantages of greater accu racy and convenience appear. So arranged it is to be used by varying the distance of the test from the person to be tested. A set of such cards is presented, of four sizes. On one the broken ring is 72. 5 millimeters in diameter. To see the break in the ring at five meters indicates vision of The other card has rings of 36. 2 and the other two cards indicate vision of 1. At 5 meters and vision of 2. At 5 meters. A table is pre sented giving the indications of these four tests at vari ous distances.To use this test, the card is held close to the patient, the break in the ring pointed out, and he is asked to indicate its direction. When he understands fully what is expected, the card is taken to a distance, the break in the ring turned in some other direction and the patient asked to indicate its new position. If unable to see the ring at that distance, it is brought nearer until the direction of the break is recognized.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.