Technic Of Refraction Trial Case And Refractive Instruments PDF Download

This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1922 edition. Excerpt: ... CHAPTER VI. THE PERIMETER OR CAMPIMETER. This instrument is for the purpose of mapping out the visual or retinal field. The essential principle is the same in every make of instrument. While the patient fixes a central fixation point, a small test-object is moved either from the periphery of an arc toward this central point or from the central point toward the periphery. The place where the test object, being thus moved, comes into the patient's indirect vision, or passes out of vision, marks the limit of the retinal field in that meridian. The test is repeated in every meridian, successively, thus giving a contour of the retinal field. The chief differences between campimeters is that, whereas the older forms are monocular, the later models are binocular or stereoscopic. Standard Registering Perimeter. f. Put the chart in place in the chart-holder behind the metal arc. 2. Seat the patient comfortably before the instrument so that his chin rests easily on the chin rest. Instruct him to fix the central fixation mark on the target. Blank the left eye. 3. Explore the visual field by moving the test object (fitted on to the long handle) from the center of the target out along the metal arc toward the periphery until the patient, who continues to fix the center, can no longer see the object. When this point is reached, indicate it on the chart by punching it through the perforation in the metal arc. 4. Revolve the metal arc to each meridian, successively, and repeat the test in each meridian. 5. When all meridians have been thus tested and marked, take out the chart and join up, with a pencil or pen, the punch marks in the chart. The result will show the visual field. 6. Repeat the process for the left eye. The Stereo-Campimeter. By means of...