Repeatability of measurements of interpupillary distance

The purpose of this study was to determine inter- and intra-examiner repeat ability of measurements of interpupillary distance (IPD), Three methods wer e used: Viktorin's, corneal reflection, and pupillometer, In Experiment 1, an experienced optometrist measured IPD on forty-nine subjects, on two occa sions, using each method. In Experiment 2, thirty-five optometrists measure d the IPD of one subject, on one occasion only, using the same three method s. The results of Experiment 1 showed that measurements of IPD differed dep ending on the method used, although the differences were small. The 95% lim its of agreement were largest with Viktorin's method and least with the pup illometer, The results of Experiment 2 also revealed a small difference in IPD between the three methods of measurement. As in Experiment 1, the 95% l imits of agreement were greatest with Viktorin's method and least with the pupillometer. Small differences in IPD were found between Viktorin's, corne al reflection and pupillometer methods of measurement. Not surprisingly, in ter-examiner repeatability was slightly poorer than intra-examiner repeatab ility. However, the differences were small enough not to be clinically sign ificant for the majority of patients. Copyright (C) 1998 The College of Opt ometrists. Published by Elsevier Science Ltd. All rights reserved.