A new portable Fresnel magnifying loupe for nystagmus observation: a clinical education and clinical practice setting study

BACKGROUND: Dizziness is a common complaint of patients treated by primary care physicians. It is predominantly caused by peripheral vestibular disorders; however, central nervous system disorders should be excluded. Examination of the eye movements and nystagmus can help differentiate the disorders of the central nervous system from the peripheral vestibular disorders; however, it is often not performed appropriately. In medical education practice, nystagmus observation may facilitate an understanding of vestibular function and nystagmus characteristics. Thus, we proposed a medical education practice to master nystagmus observation using a recently developed portable Fresnel magnifying loupe that could be shielded by one eye. METHODS: Thirty-three students from the Department of Physical Therapy and the Department of Speech, Language, and Hearing Therapy of the Mejiro University participated in this study. Postrotatory nystagmus was measured and compared using the new loupe and control methods, namely the naked eye and Frenzel goggles; we rated the ease of visibility using a five-point scale. RESULTS: The number of detected cases of nystagmus was significantly higher with the new loupe than with the naked eye (p = 0.001). In addition, there were no significant differences in the nystagmus counts between the observations using the new loupe and Frenzel goggles (p = 0.087). No significant difference was observed in the visibility of eye movements between the loupe and naked eye (p = 1.00). The Frenzel goggles provided better visibility compared to that by the loupe (p = 0.034); however, none of the participants reported poor visibility using any of these methods. CONCLUSIONS: Our newly developed Fresnel loupe allows for the observation of nystagmus counts a level of reduction in fixation suppression similar to that of Frenzel goggles in an educational practice setting. Furthermore, it enables the detection of significantly more nystagmus counts compared to that by the naked eye. It offers several advantages over Frenzel goggles, including its lightweight, thin, durable, and portable design. Additionally, the loupe does not rely on a power source and can be used under normal room lighting conditions. TRIAL REGISTRATION: This study was approved by the Medical Research Ethics Committee of Mejiro University (approval number: 21medicine-021).