Occurrence of Physiologic Gaze-Evoked Nystagmus at Small Angles of Gaze

摘要

Purpose.: Physiologic gaze-evoked nystagmus (GEN) is one of many normal eye movements seen on the neurologic examination. GEN occurring at gaze angles 45?° is considered a positive sign in the Horizontal Gaze Nystagmus Test (HGNT) used by United States police officers to determine alcohol intoxication. Methods.: The authors enrolled 56 subjects after a brief survey and a neurologic examination yielding normal results. Subjects were directed to look at small targets on the wall in primary gaze and at 10?° intervals until they reached extreme gaze bilaterally. Eye movements were recorded using infrared video-oculography. Results.: In addition to a high incidence of physiologic GEN at gaze angles 30?° and greater (at 30?°, n = 43%; at 40?°, n = 73%; at extreme gaze, n = 93%), the authors demonstrated that physiologic GEN occurs at smaller gaze angles (at 10?°, n = 21%; at 20?°, n = 34%). Conclusions.: A significant number of subjects with normal vision have physiologic GEN at gaze angles as small as 10?°. This could potentially refute the a??failinga?? grade that is the hallmark of the HGNT and propagates further testing of the validity of this test in the conviction of intoxicated drivers.