Myopia-correcting lenses decrease eye fatigue in a visual search task for both adolescents and adults.

The steady, world-wide increase in myopia prevalence in children over the past decades has raised concerns. As an early intervention for axial-length-related myopia, correcting lenses have been developed (such as Defocus Incorporated Multiple Segment (DIMS) lenses), which have been shown to be effective in slowing myopia progression. Beyond this direct effect, however, it is not known whether such lenses also affect other aspects important to the wearer, such as eye fatigue, and how such effects may differ across age, as these lenses so far are typically only tested with adolescents. In the present work, we therefore investigated perceived fatigue levels according to lens type (normal vs DIMS) and age (adolescents vs adults) in a demanding visual search task ("Finding Wally") at two difficulty levels (easy vs difficult). Whereas age and difficulty did not result in significant differences in eye fatigue, we found a clear reduction of fatigue levels in both age groups when wearing the correcting lenses. Hence, the additional accommodation of these lens types may result in less strain in a task requiring sustained eye movements at near viewing distances.

Bilberry extract supplementation for preventing eye fatigue in video display terminal workers.

OBJECTIVES: To examine the effect of a dietary supplement containing bilberry extract (BE) on eye fatigue induced by acute video display terminal (VDT) loads. DESIGN AND SETTING: A prospective, randomized, double-blind, placebo-controlled study was performed from August 2012 to February 2013 in the Medical Corporation Jico-kai Yagi Hospital, and the Shinyokohama Shinoharaguchi Orthopedic Surgery and Dermatology Clinic, in Japan. PARTICIPANTS: Two hundred eighty-one office workers aged 20-40 years that used VDTs were screened by critical flicker fusion (CFF) and near point accommodation (NPA). INTERVENTION: The participants were randomized to either a BE (480 mg/day) or placebo (vehicle) group, and took allocated capsule, daily, for 8 weeks. MEASUREMENTS: The CFF, NPA, contrast visual acuity, functional visual acuity, keratoconjunctival epithelial damage, and fluorescein tear film break-up time were examined, and 18 subjective symptoms of eye fatigue were evaluated by questionnaire. Adverse events were reported via medical interviews. Data were collected both before and after VDT load at baseline, and 4, and 8 weeks after daily supplementation with either BE or placebo. RESULTS: Of 281 participants screened, 88 having relatively lower levels of CFF and NPA were enrolled in the study. Of these, 37 control and 43 BE group subjects completed the study. The VDT load-induced reduction in CFF was alleviated after 8 weeks of BE supplementation (95% confidence interval, 0.10-1.60; p=0.023), in contrast to placebo supplementation, while NPA variation was not. Of the subjective symptoms of eye fatigue, VDT load-induced ocular fatigue sensation, ocular pain, eye heaviness, uncomfortable sensation, and foreign body sensation were mitigated more in the BE group than in the control group, at week 8 (p<0.05). There were no severe adverse events in either group. CONCLUSIONS: BE supplementation improved some of the objective and subjective parameters of eye fatigue induced by VDT loads.

Visual fatigue caused by watching 3DTV: an fMRI study.

The objective of this study is to observe the visual fatigue caused by watching 3DTV using the method of functional magnetic resonance imaging (fMRI). The data of fMRI during three kinds of visual stimulation tasks were obtained from twenty subjects. At first, blood-oxygen-level dependent (BOLD) signal changes during stimuli of checkerboard task were compared before and after one-hour watching 3D/2DTV, and subjective evaluation was conducted based on the questionnaire simultaneously. Then 3D and 2D images were used to stimulate healthy individuals to measure brain activities that correlated with stereoscopic vision. Finally, the relationship between front or back depth of field images and visual fatigue was investigated. The results reveal that the 3D group shows more significant differences of brain activities in BA8, BA17, BA18 and BA19 than the 2D group during the checkerboard stimulation. BA5, BA6, BA7 and BA8 were testified to have close relationship with stereoscopic perception via the 2D/3D images stimulation. Furthermore, the front depth of field image was proven to impose a more serious impact on visual fatigue than the back one. These conclusions are useful for healthy and reasonable 3DTV watching as well as properly designing of 3D scenes.

Usage of stereoscopic visualization in the learning contents of rotational motion.

Rotational motion plays an essential role in physics even at an introductory level. In addition, the stereoscopic display of three-dimensional graphics includes is advantageous for the presentation of rotational motions, particularly for depth recognition. However, the immersive visualization of rotational motion has been known to lead to dizziness and even nausea for some viewers. Therefore, the purpose of this study is to examine the onset of nausea and visual fatigue when learning rotational motion through the use of a stereoscopic display. The findings show that an instruction method with intermittent exposure of the stereoscopic display and a simplification of its visual components reduced the onset of nausea and visual fatigue for the viewers, which maintained the overall effect of instantaneous spatial recognition.

3D asthenopia in horizontal deviation.

PURPOSE: This study was conducted to investigate the asthenopic symptoms in patients with exotropia and esotropia while watching stereoscopic 3D (S3D) television (TV). METHODS: A total 77 subjects who more than 9 years of age were enrolled in this study. We divided them into three groups; Thirty-four patients with exodeviation (Exo group), 11 patients with esodeviation (Eso group) and 32 volunteers with normal binocular vision (control group). The S3D images were shown to all patients with S3D high-definition TV for a period of 20 min. Best corrected visual acuity, refractive errors, angle of strabismus, stereopsis test and history of strabismus surgery, were evaluated. After watching S3D TV for 20 min, a survey of subjective symptoms was conducted with a questionnaire to evaluate the degree of S3D perception and asthenopic symptoms such as headache, dizziness and ocular fatigue while watching 3D TV. RESULTS: The mean amounts of deviation in the Exo group and Eso group were 11.2 PD and 7.73PD, respectively. Mean stereoacuity was 102.7 arc sec in the the Exo group and 1389.1 arc sec in the Eso group. In the control group, it was 41.9 arc sec. Twenty-nine patients in the Exo group showed excellent stereopsis (≤60 arc sec at near), but all 11 subjects of the Eso group showed 140 arc sec or worse and showed more decreased 3D perception than the Exo and the control group (p < 0.001, Kruskal-Wallis test). The Exo group reported more eye fatigue (p < 0.001, Kruskal-Wallis test) than the Eso and the control group. However, the scores of ocular fatigue in the patients who had undergone corrective surgery were less than in the patients who had not in the Exo group (p < 0.001, Kruskal-Wallis test) and the amount of exodeviation was not correlated with the asthenopic symptoms (dizziness, r = 0.034, p = 0.33; headache, r = 0.320, p = 0.119; eye fatigue, r = 0.135, p = 0.519, Spearman rank correlation test, respectively). CONCLUSION: Symptoms of 3D asthenopia were related to the presence of exodeviation but not to esodeviation. This may indicate that S3D symptoms are closely related to the convergence demand.

Autokinetic movement of an induced afterimage.

Thirty-two female Ss participated in an experiment in which autokinetic movement (AKM) direction change frequency of an induced afterimage was assessed as a function of stimulus afterimage color (yellow or blue-green) and the presence or absence of eye strain. Afterimage color was found not to affect AKM frequency reports. However, eye strain significantly (p less than .002) affected such reports, with the fewest AKM direction changes reported when strain was present. These results were explained in terms of an error signal and noise analysis of AKM.