Objective In recent years, it has been reported that the ingestion of bilberry extract improves visual function. However, few clinical studies have investigated the efficacy of bilberry extract for the improvement of eye fatigue-related symptoms that are induced by visual display terminals（VDT）. Therefore, we examined the safety and efficacy of bilberry extract （BILBERON^®）in the treatment of VDT-induced eye fatigue-related symptoms.
Methods In this human trial, healthy adult subjects with subjective eye fatigue who were exposed to VDT work for over 4 h/day were recruited. The subjects were randomly divided into two groups（n＝10 for the test product group and n＝11 for the placebo group）and orally ingested either 160 mg/day of BILBERON^® or the placebo capsule for 6 weeks. The VDT was loaded on the examination days before and after the 6-week ingestion period. A Schirmer's test was performed before the VDT load to assess eye dryness, and the following investigations were performed before and after the VDT load: miosis frequency（MF）, near point pupil diameter（NPD）, and far point pupil diameter（FPD）examination to determine the accommodative function, critical flicker frequency（CFF）to assess eye fatigue, and a Likert scale questionnaire to assess subjective symptoms.
Results Significant improvements were observed in the MF, variation between NPD and FPD, ratio of Schirmer value and subjective symptoms, including an eye fatigue sensation and a neck and shoulder stiffness sensation, of the test product group after the 6-week ingestion period compared to those of the placebo group. Moreover, the CFF（red light）, as a measure of eye fatigue, was less in the placebo group compared to that of the test product group, which suggests that the accumulative eye fatigue was suppressed in the test product group.
Discussion Healthy subjects with subjective eye fatigue showed improvements in their VDT-induced eye fatigue-related symptoms, including accommodative function, eye fatigue, eye dryness, subjective symptoms of eye fatigue sensation, and neck and shoulder stiffness sensation, following an ingestion of 160 mg/day bilberry extract（BILBERON ^®）for 6 weeks. In addition, the test product appeared to be safe under the conditions employed in the present study.