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326are not always symptomatic23, 24) and thus subjec-tive assessment may not be trustworthy. In cases of glaucoma, the loss of optic nerve fibers starts not only long before it is sensed, but also before the defects can be detected by perimetry, and visual field defects rarely occur at the same area in both eyes23). Therefore, patients may fail to notice their glaucoma-related visual field defects on their own before progression to a late stage when their central visual fields are affected23).Considering these common characteristics, general screening using objective assessment is effective and essential in workplaces when there is a high prevalence of the conditions underlying health-re-lated accidents, subjective manifestations are scarce, or the consequences of accidents can be expected to be quite serious.Our approach to glaucoma to prevent HRTA: CLOCK CHART®There are many individuals with latent glaucoma who need screening, appropriate diagnosis and treatment for prevention of traffic accidents. A simple screening method, which even busy gener-alists can use in their outpatient clinics, is urgently needed. CLOCK CHART® could be a handy visual field screening tool.CLOCK CHART® as a promising tool for prevention against HRTACLOCK CHART® is a self-administered visual field screening tool25). Illustrations of a ladybug, a caterpillar, a butterfly and a cat are depicted on circumferences of eccentricity zones 10°, 15°, 20° and 25° away from the center, respectively (Figure 1), when the examinee stares at the center from 35 cm above25). Then, an examiner can identify visual field defects of examinees by confirming if the illustration remains visible to them as CLOCK CHART® rotates25) (Figure 2).The sensitivity of visual field screening using CLOCK CHART® was 87%, 93%, and 97 % for the mean defect (MD) value in early, moderate, and severe glaucoma, respectively (early <6 dB, moderate 6 dB≦MD≦12 dB and severe >12 dB), and the specificity was 89 %25). This high efficacy was confirmed by our preliminary study26): the visual fields of 5 individuals with glaucoma were examined using both a Humphrey Field Analyzer and CLOCK CHART®. We divided the visual field of 5 patients into 4 areas, namely the superior and inferior areas of the right and left eyes. Of the 20 areas, the Humphrey Field Analyzer detected visual field defects in 60% of the areas, while CLOCK CHART® detected defects in 45%. Their agree-ment rate was 85%. CLOCK CHART® binocular Figure 1　CLOCK CHART®Figure 2