Development of a screening system for central visual field using the eye-tracking device\n

　Background: Visual field test with gaze movements do not require a subjective response because they are based on reflexive movements. In this study, we developed a visual field test system with gaze movements to perform a central visual field screening, and then examined the reproducibility of the measurements in healthy adult volunteers.　Methods: We examined 30 right eyes of 30 healthy volunteers (mean age, 22.7 ± 5.2 years) with a best-corrected visual acuity of at least 20/20. Gazefinder, an eye-tracking device, was used to measure gaze movements. Subjects with refractive correction were asked to follow a white target presented on a monitor. If a subject can accurately perform eye tracking with respect to the visual target, visual field with gaze movements measurements are theoretically possible in eight directions (horizontal/vertical to 15.3° and oblique to 21.5° ). After a total of three measurements, the data were quantified using analysis software (CreateChart). Finally, the intraclass correlation coefficients of the measurement values were obtained.　Results: The difference between theoretical and actual measurement values, which is thought to reflect gaze accuracy, were –0.1° ± 0.9° for upper, –0.6° ± 1.0° for upper right, –0.2° ± 1.0° for right, –0.8° ± 0.9° for lower right, –0.5° ± 0.7° for lower, –0.5° ± 0.9° for lower left, –0.6 ° ± 0.5 ° for left, and –0.6 ° ± 0.5 ° for upper left. No significant differences were found among the eight directions, and gaze accuracy was high, at within 1°. The intraclass correlation coefficients were 0.6 or higher in each direction (P < 0.01), indicating high repeatability.　Conclusions: In the traditional method for measuring visual field with gaze movements, the fixation point of view needs to be reset for each gaze movement. On the other hand, the system developed in this study has the advantage of not requiring eye movements to return to the fixation point. The present findings indicate that our newly developed system is a useful device when standard perimetry is difficult to measure

Nanometer-size hard magnetic ferrite exhibiting high optical-transparency and nonlinear optical-magnetoelectric effect

Development of nanometer-sized magnetic particles exhibiting a large coercive field (Hc) is in high demand for densification of magnetic recording. Herein, we report a single-nanosize (i.e., less than ten nanometers across) hard magnetic ferrite. This magnetic ferrite is composed of ε-Fe2O3, with a sufficiently high Hc value for magnetic recording systems and a remarkably high magnetic anisotropy constant of 7.7 × 106 erg cm−3. For example, 8.2-nm nanoparticles have an Hc value of 5.2 kOe at room temperature. A colloidal solution of these nanoparticles possesses a light orange color due to a wide band gap of 2.9 eV (430 nm), indicating a possibility of transparent magnetic pigments. Additionally, we have observed magnetization-induced second harmonic generation (MSHG). The nonlinear optical-magnetoelectric effect of the present polar magnetic nanocrystal was quite strong. These findings have been demonstrated in a simple iron oxide, which is highly significant from the viewpoints of economic cost and mass production.UTokyo Research掲載「世界最小ハードフェライト磁石の開発に成功」 URI: http://www.u-tokyo.ac.jp/ja/utokyo-research/research-news/the-worlds-smallest-hard-ferrite-magnet.htmlUTokyo Research "The world\u27s smallest hard ferrite magnet" URI: http://www.u-tokyo.ac.jp/en/utokyo-research/research-news/the-worlds-smallest-hard-ferrite-magnet.htm

Development of a screening system for central visual field using the eye-tracking device\n

Regular Articlejournal articl