Methods

As n fixation object a reflex hammer was nsed, covered with a piece of hright red material, retained by the rubber ring, in order to make the fixation-point more distinct. To obtain the same fixation distance and the same deviation to the sagittal plane, a protractor was attached to the subject's forehead by an adjustable band around the head. At the angle of 45 degrees on each side of the sagittal plane, red riders were applied to the protractor. A long thread of 90 cm., starting from the centre of the protractor, was supplied a t the other end with a ring into which tjhe reflex hainrner could be inserted. The length of the thread, 90 crn., was chosen to prevent the subject from accommodating too much and also, from the practical point of view, to suit the examiner's armlength when the fixation object was moved from one side to another. The apparatus is shown in figures I and 11. The angle ))a)) was fitted so that the fixation object moved in a plane approximately through the tip of the nose.