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390KVA has also been observed in young and middle-aged soccer players (n = 44) and in nonathletes of the same age group (n = 45)25). Recently, Kudo et al. reported kendo players (n = 41; 35.4 ± 15.7 years, range 19-65 years) had significantly higher KVA (p < 0.01) than nonexercisers (n = 65; 38.1 ± 17.1 years, range 19-71 years)26).Therefore, KVA declines with age, and training habits to gaze at moving objects, such as kendo, may suppress the age-related decline. However, the effect of sports remains unclear.Effects of DHA and astaxanthin on KVADHA is an n-3 fatty acid found in the retina and the brain’s gray matter27). In 1993, artificial milk containing fish oil was reported to improve visual acuity in preterm infants up to the fourth month of life28). This research led to the study of the effect of DHA on KVA.In 1997, Sawaki et al. reported a randomized, double-blind study to examine the effects of DHA (1,500 mg/d) for 35 consecutive days in 44 male collegiate athletes and baseball players with an SVA of 1.0 or higher29). DHA intake significantly increased KVA from 0.87 ± 0.24 to 0.97 ± 0.21 (p < 0.01) but did not change SVA. The improvement was greater in participants with low KVA before intervention. No change was observed in the control group (equal amounts of soybean oil)29).To confirm the results of Sawaki et al.29), Ishigaki et al. conducted a double-blind study of DHA (1,500 mg/d) for 30 consecutive days in 20 univer-sity long-distance runners and 12 fencing players30). The mean SVA significantly increased from 1.21 to 1.32 in the DHA group (p < 0.05), whereas there was no significant change in the placebo (safflower oil) group. The mean KVA improved from 0.65 to 0.69 in the DHA group, but not significant30).Subsequently, another study was conducted with 55 college athletes as participants: 8 tennis players, 18 volleyball players, 15 track-and-field athletes, and 14 baseball players (47 men and 8 women)31). A total of 28 participants did not take orthoptics, whereas 25 and 2 of them used contact lenses and glasses, respectively. DHA (1,500 mg/d) was given for 35 consecutive days, and their visual acuity was measured before and after the intervention. There were no significant differences in SVA and KVA between the groups (25 and 26 in the DHA and control groups, respectively). Low-contrast visual acuity improved in the DHA group but not in the control group (p < 0.05). When preintervention KVA was stratified by LogMAR = 0.3 (decimal acuity 0.5), subjects with lower preintervention KVA improved in the DHA group (n = 10) but not in the control group (n = 13; between-group comparison, p < 0.05). Therefore, DHA may improve KVA in subjects with low KVA31).Sawaki et al. also determined the effect of astax-anthin. A total of 18 male collegiate handball players ingested astaxanthin (6 mg/d, n = 9) or placebo (n = 9) for 4 weeks. No significant improvement was observed on SVA, KVA, or KVA/SVA32).This review aimed to outline the history of KVA followed by the studies on KVA conducted at Juntendo University Faculty of Health and Sports Science. Suzumura defined KVA as the ability to recognize an object moving back and forth in the distance against the observer, and invented a device to measure KVA. Studies on KVA has been conducted at Juntendo University Faculty of Health and Sports Science since 1990s. Athletes who require great attention to moving objects have a higher KVA. Further, athletes at higher levels of competition have higher KVA. The relationship of KVA to simple reaction time is unclear. In contrast, some studies suggest a correlation between KVA and peak latency of visual-evoked potentials. However, the mechanism to determine KVA requires more investigations. Alternatively, KVA represents a potential tool for discovering junior sports talent as it cannot be improved by training after 8 years old. Moreover, KVA declines with age although habitual exercise that requires a clear, quick vision of a moving object may suppress the age-related decline of KVA. In addition, DHA may improve KVA in subjects with low KVA. As described above, KVA is a unique visual acuity distinct from SVA. However, further studies are necessary to determine the practical application of KVA.The authors would like to thank the editorial board of Juntendo Medical Journal for encouraging us to prepare this review. The authors would also like to thank Kowa (Nagoya, Japan) for providing SummaryAcknowledgments