Abstract

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±3.2°/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) °/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.

• Keywords: Frenzel glasses;Visual fixation;Diopter;Fresnel lens;Spontaneous nystagmus;