Masakazu Hirota

Senior Assistant Professor, Faculty of Medical Technology, Teikyo University *Profile is at the time of the award.

2022Inamori Research GrantsBiology & Life sciences

Research topics
Vision Performance Management in the Digital Era: Development of a Device for Simple Quantitative Evaluation of Visual Fatigue and Detection of Appropriate Distance for Smartphone Use
Recently, smartphones and other digital devices have become so popular worldwide that each person now has at least one of them. Digital devices have become an indispensable part of our lives. On the other hand, the number of patients complaining of visual fatigue due to digital devices is rapidly increasing and has become an international health issue. However, no test method has been established to quantitatively evaluate visual fatigue.
In a previous study, I developed a binocular fusion maintenance test, which was independent of aging and reproducible in the quantitative evaluation of visual fatigue. In this study, I will optimize a device that can be used in clinical practice to evaluate binocular fusion maintenance and investigate the relationship between smartphone use and ocular fatigue.


New digital devices are expected to continue to be developed and widespread in the future. Visual fatigue varies according to individual senses. I hope to reduce the number of patients suffering from visual fatigue caused by digital devices by quantifying the fuzziness of visual fatigue.

Outline of Research Achievments

In this study, I simplified the binocular fusion maintenance test developed in a previous study to evaluate visual fatigue. I succeeded in reducing the size of the device and the test time from 50 to 30 seconds while maintaining the measurement accuracy. Then, I investigated the optimal viewing distance using a smartphone to avoid visual fatigue. My results suggested that use at a viewing distance of 50 cm is preferable to reduce the risk of smartphone-induced visual fatigue.

  1. Morimoto T, Hirota M et al. (2023)  Light-field visual system for the remote robot operation interface. IEEE/RSJ International Conference on Intelligent Robots and Systems 2023, 7020-7025.

  2. Hirota M and Watanabe M (2023)   Dry eye and visual fatigue.  Monthly Book OCULISTA 128,  pp.29-34 ( in Japanese). 

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Biology & Life sciences