In short, in using the Ski-optometer, it is not necessary to constantly watch the registrations during examinations. The automatic operation of the instrument is an exclusive feature, so that the refractionist should unhesitatingly employ it. Hence, by eliminating the perpetual watch on the lenses in use, the refractionist is enabled to give his undivided attention to the patient rather than to the trial lenses. Where a special dark-room is used for skioscopic work, an additional wall bracket or floor stand will necessitate only the removal of the instrument itself. This enables the refractionist to use the Ski-optometer for subjective or objective work, without disturbing the patient’s correction. CHAPTER IV IMPORTANT POINTS IN CONNECTION WITH THE USE OF THE SKI-OPTOMETER The Ski-optometer is equipped with an adjustable head-rest, permitting its lenses to be brought as close as possible to the eye without touching the patient’s lashes, a matter of importance in every examination. [Illustration: Fig. 11—The nasal lines of the Ski-optometer fit the contour of face with mask-like perfection, patient remaining in comfortable position.] ELIMINATION OF TRIAL-FRAME DISCOMFORT Where the Ski-optometer is correctly fitted to the face, the patient invariably remains in a comfortable position (Fig. 11). The instrument is shaped to fit the face like a mask, so that even with a pupillary distance of but 50 m/m (that of a child) there still remains, without pinching, ample room for the widest nose of an adult. Before making an examination, the correct pupillary distance should always be obtained by drawing an imaginary vertical line downward through the center of each eye from the 90° point on the Ski-optometer axis scale. The pupillary distance will then register in millimeters on the scale of measurements for each eye separately. If the Ski-optometer is correctly adjusted, the patient is securely held in position, the cumbersome trial-frame being entirely eliminated. RIGIDITY OF CONSTRUCTION Illustration on following page (Fig. 11a) shows the reinforced double bearing arms which hold the Ski-optometer lens batteries at two points. This eliminates possibility of the instrument getting out of alignment, and prevents wabbling or loose working parts. The broad horizontal slides shown in the cut, move in and out independently so that the pupillary distance is obtained for each eye separately by turning the pinioned handle on either side of the instrument. The scale denotes in millimeters the P.D. from the median line of the nose outward, the total of both scales being the patient’s pupillary distance. Fig. 11a also serves to show the staunch construction of the base of the Ski-optometer. [Illustration: Fig. 11a—Showing staunch construction of Ski-optometer base.] HOW TO PLACE THE SKI-OPTOMETER IN POSITION