Clinical Usefulness of Fresnel Ganzfeld Stimulator

PURPOSE: To compare electroretinogram (ERG) waveforms acquired using a ganzfeld stimulator and a Fresnel ganzfeld stimulator. METHODS: ERGs were recorded with a ganzfeld stimulator and a Fresnel ganzfeld stimulator from both eyes of 25 volunteers. Peak-to-trough amplitudes and peak implicit times were compared between both eyes and between a ganzfeld stimulator and a Fresnel ganzfeld stimulator. ERGs taken from the sitting and supine positions were also compared using the Fresnel ganzfeld stimulator. RESULTS: There was no statistically significant difference between the Fresnel ganzfeld stimulator and dome-shaped ganzfeld stimulator in amplitude and implicit time of dark adapted 0.01, 3.0 ERG, photopic 3.0 ERG, photopic 3.0 flicker. The differences in amplitude and implicit time between the right and left eyes were not influenced by the Fresnel ganzfeld stimulator. Additionally, no differences were observed in ERGs obtained from the sitting and supine positions using the Fresnel ganzfeld stimulator. CONCLUSIONS: The newly developed ganzfeld stimulator with a sealed Fresnel lens can be considered as a reliable alternative method for measuring ERGs. Fresnel ganzfeld stimulator is useful for patients having problems with mobility or uncooperative children.

Competence in Suppressing the Visual Fixation among Different Types of Frenzel Glasses / 대한평형의학회지

BACKGROUND AND OBJECTIVES: Several manufacturers supply different types of Frenzel glasses, but the quality of these varied Frenzel glasses seems to be quite different. The aim of this study was to compare the competence in suppressing visual fixation (VF) among different types of Frenzel glasses. The second aim was to develop a new type of Frenzel glasses which is cheaper and more convenient to carry, but has an equivalent competence. MATERIALS AND METHODS: Four different types of Frenzel glasses were evaluated: 30 diopter Frenzel glasses manufactured by Nagashima (N), 10 diopter Frenzel glasses manufactured by Jungang (J), 13 diopter conventional magnifying glasses (M) and 17 diopter Fresnel lens glasses assembled by the authors. The amplitude of the spontaneous nystagmus (SN) was measured though the electronystagmography system. The SN was measured 35 times from 15 patients who were diagnosed as vestibular neuritis. RESULTS: The mean amplitude of the SN was 8.8+/-3.2degrees/sec when measured with the videonystagmography goggles. When the same SN was measured through the 4 different Frenzel glasses, it was 7.5+/-2.8 (N), 6.3+/-3.0 (F), 6.2+/-3.0 (M), and 5.7+/-2.6 (J)degrees/sec respectively. The amplitude of the SN was significantly bigger when wearing the N glasses compared to the other 3 glasses. The SN was significantly smaller when wearing the J glasses compared to the F glasses. CONCLUSION: The competence of suppressing VF was significantly different among the varied types of glasses. The F glasses seem to have a similar or better competence with the J glasses. F glasses seems to be a fairly good alternative which is very portable and cheap.