Portable Howell heterophoria measurement device

In this study, we used a compound vision card consisting of Howell's and Thorington's vision card on both sides, and placed a prism or a Maddox 's lens in the left eye of the subjects to establish the subjective measurement technique of heterophoria. When a prism with 6 prism diopters and the base upward was placed in front of the left eye of the subject to look at the front of the compound vision card at 45 cm, it was observed that the Howell vision card was separated into two vision cards. After confirming the relative position of the point of the upper and lower vision cards, the subject move the paddle on the measuring device to make the paddle overlap the point of the upper vision card, judge the left and right directions of the point and read number of the horizontal base line, and then measure the line of sight deviation of the near horizontal heterophoria. In this study, 5 subjects with normal vision were tested with von Graefe, Howell and This innovative device for near distance horizontal esotropia. The test results showed that 85% of the subjects were exotropia, and the difference of the three measurements was within one prism diopter (±1Δ). It is proved that the reliability of the measuring device is excellent.