CHAPTER XII A CONDENSATION OF PREVIOUS CHAPTERS ON THE PROCEDURE FOR MUSCLE TESTING WITH THE SKI-OPTOMETER 87 Four Methods of Treating an Imbalance Case when the Preceding One Fails 90 Prisms 92 Cyclophoria 92 CHAPTER XIII CYCLOPHORIA 93 Made with Maddox Rods and Rotary Prisms 93 CHAPTER XIV CYCLODUCTION TEST 99 Made with the Combined Use of the Two Maddox Rods 99 Treatment for Cyclophoria 102 CHAPTER XV MOVEMENTS OF THE EYEBALLS AND THEIR ANOMALIES 105 Monocular Fixation 105 Binocular Fixation 106 Orthophoria 107 Heterophoria 107 Squint 108 Varieties of Heterophoria and Squint 109 CHAPTER XVI LAW OF PROJECTION 114 Suppression of Image 115 Monocular Diplopia 115 Table of Diplopia 116 Movement of Each Eye Singly 117 Subsidiary Actions 118 Field of Action of Muscles 120 Direction of the Gaze 120 Primary Position—Field of Fixation 121 Binocular Movements 121 Parallel Movements 122 Lateral Rotators 123 Eye Associates 124 Movements of Convergence 125 Movements of Divergence 125 Vertical Divergence 126 Orthophoria 126 Heterophoria 126 Subdivisions 126 CHAPTER XVII SYMPTOMS OF HETEROPHORIA 128 Treatment 130 Destrophoria and Laevophoria 132 The demands of the day for maximum efficiency in the refracting world are largely accountable for the inception, continuous improvement and ultimate development of the master model Ski-optometer.