The rapid development of information communication technology has led to the wide acceptance of virtual reality in entertainment and other industries. Along with the growing number of people working in virtual reality, the measures to cope with cybersickness have become increasingly important. In this review, the factors that cause cybersickness, methods to estimate symptoms,related visual and autonomic nervous functions, and measures to address biomedical problems are discussed. In addition, the expanded mismatch hypothesis is introduced.

　Recently, various head mounted display for VR-system have been developed. However a new problem of natural 3D visualization has now arisen. This paper considers the characteristics of hyper realistic displays, especially 3D display. Specifically, the following items are examined from the point of view of human visual function.
　1）The relationship between extremely high-resolution display and resolution（vernier acuity）, frame-rate（stable fusion frequency）on visual function. 2）The relationship between hyper realistic displays and the viewing angle. 3）The unnaturalness（distortion of space perception, such as the cardboard effect, lack of motion parallax, and so on）of conventional stereoscopic displays. 4）Three-dimensional display system suited to display space.

　Increasing popularity and usage of head mounted displays have led to virtual reality（VR）becoming more accessible. Consequently, the issue regarding the reduction of the incidence of visually induced motion sickness（VIMS）in VR environments has been drawing attention. Although the generative causes for VIMS are not well known, the sensory conflict theory has been widely accepted as the explanatory hypothesis for VIMS generation. Visually induced self-motion（vection）, which is often discussed in relation to VIMS, can be explained by the visual-vestibular conflict theory. Based on the said theories and empirical data, it has been observed that the causative conditions for vection need not always coincide with the causative conditions for VIMS. Measurement methods for VIMS primarily include psychological methods such as subjective evaluation, and physiological methods concerning autonomic nervous activity. By employing such measurement methods, characteristics of visual motion factors（such as velocity ranges and axes of visual rotation）are being studied as the inducing factors for VIMS. Furthermore, in the ergonomics committee of International Organization for Standardization, they are attempting to scale the severity of VIMS in terms of the factors that influence VIMS. Based on the said scale, ergonomic guidelines are being developed for reducing the incidence of VIMS.

Recently, virtual reality（VR）has gained attention as a novel tool to support the improvement of athletes’ motor performance, such as that required in professional sports teams. Moreover, in the field of sports psychology, VR has also been used as an evaluation tool to investigate athletes’ anticipatory skills, which include anticipating future events（e.g., shot directions）from the opponents’ action or the ball trajectory. In this paper, we explain the features of visual information underpinning skilled anticipation, which were identified using VR technology. Through a research finding regarding baseball batting training using VR, we will further discuss VR training and its future direction.

Our study examined the use of virtual reality（VR）in neurorehabilitation. Experiment 1 aimed to verify the relationship between sensory information processing in the right parietal cortex to maintain standing balance and optokinetic nystagmus（OKN）. Transient inhibition of the parietal area was induced using a transcranial direct current stimulation（tDCS）device. Postural stability and OKN were measured pre- and post-cathodal tDCS. We found that sensory information processing in the right parietal cortex was related to OKN and maintaining standing balance in the eyes open condition. Experiment 2 used a smartphone head mounted display（S-HMD）to provide fully immersive virtual environments. Postural stability in static standing and with one leg standing in open and closed eyes conditions was measured pre- and post-optokinetic stimulation（OKS）delivered using the S-HMD. We found that postural control was improved in all conditions. Brain activation as part of neurorehabilitation before exercise might increase the effects of rehabilitation. Consumer HMDs have potential as devices that allow widespread use of VR in neurorehabilitation across clinical sites. We hope to promote neurorehabilitation using HMDs in the future.

In this study, we examined the psychophysical causes of illusions by changing the constituent elements of figures, such as inclination, size, contrast, and angle, in 30 healthy adult subjects.
As a result, changes of inclination, size, and angle were involved in the appearance and disappearance of the illusion in Müller-Lyer, Hering and Ebbinghaus figures. In addition, a change in the contrast resulted in no differences; however, this is in contrast to what was previously believed. Therefore, the perception of an illusion was affected by changes in inclination, size, and angle but not by changes of contrast.

　We report the case of a 12-year-old boy with homonymous hemianopia caused by neuromyelitis optica spectrum disorder（NMOSD）. He was referred to our hospital due to decreased visual acuity. His corrected visual acuity was 1.2 in both eyes. His pupillary response was prompt without relative afferent pupillary defect. Bilateral optic discs appeared normal. Visual field examinations showed left homonymous hemianopia. Optical coherence tomography revealed thinning of the inner retinal layer of the macula that was consistent with homonymous hemianopia. Head fluid-attenuated inversion recovery magnetic resonance imaging（MRI）showed a hyperintense lesion continuous from the hypothalamus to the third ventricle. A blood test showed that he was positive for anti-aquaporin-4 antibody and negative for anti-myelin oligodendrocyte glycoprotein antibody and anti-N-methyl-D-aspartate receptor antibody. Consequently, he was diagnosed with NMOSD. Cerebrospinal fluid test results were normal. He was admitted to the pediatric ward and started on 1000 mg methylprednisolone per day for 3 days. This was repeated for another cycle. We have been gradually reducing the dose of methylprednisolone and he is currently taking 25 mg per day. MRI showed a decrease in the size of the lesion, and although he still has left homonymous hemianopia, it is improving.
　NMOSD commonly occurs in middle-aged woman. The present case occurred in a 12-year-old boy who presented with left homonymous hemianopia, probably caused by the right occipital lesion.

　Patients with hypertrophic pachymeningitis have onset of visual deterioration due to inflammatory change involving the visual pathway usually accompanied by severe pain. We report a 56-year-old female patient with hypertrophic pachymeningitis who initially presented chronic headache and bitemporal hemianopia. She visited our hospital complaining of the loss of vision and visual field defects of 1-month duration and exacerbated headache of few days’ duration, that was associated with chronic ocular pain and headache for 1 year. She had suffered from rheumatoid arthritis（RA）for a decade which was well controlled by immunosuppressive drugs; serological test revealed the absence of auto-antibodies and rheumatoid factor. Visual acuity was（0.4）at OD and（0.6）at OS, and there was limitation of supraduction and moderate mydriasis at OD. Static visual field examination revealed bitemporal hemianopia. Enhanced magnetic resonance imaging revealed the presence of the enhanced thickened pachymeninx at the base of the skull and pituitary gland swelling due to inflammation spread to the right cavernous sinus and pituitary gland. We diagnosis of hypertrophic pachymeningitis was made, and subsequently, steroid mini-pulse therapy was administered at our hospitals’ Department of Internal Medicine. Immediately following steroid therapy, her bilateral visual acuity improved to（1.2）； the limitation of supraduction at OD improved 2 months later and bitemporal hemianopia improved 4 months later. Our findings suggested that the patient developed bitemporal hemianopia due to compression of the pituitary gland caused by inflammatory change involving the pituitary gland with accompanied chronic mild headache since severe headache was masked by the long-term use of immunosuppressive and analgesic drugs. Patients with hypertrophic pachymeningitis with RA as underlying disease were rarely reported; this case report highlights the atypical clinical course of the disease.

Purpose: To investigate the functional and morphologic changes that occur in ethambutol（EMB）-induced ocular toxicity in rabbit models and concomitantly evaluate the role of zinc（Zn）in EMB toxicity.
Method: Eight eyes of four pigmented rabbits were used. EMB was orally administered to all rabbits at 110-180 mg/kg/day for 20 weeks. Two of these rabbits were also given Zn supplementation at a dose of 8 mg/kg/day. As functional evaluations, infrared pupillography and electroretinography were examined. All the EMB-treated rabbits were euthanized and the globes including the optic nerves were harvested. Histopathologic examination of harvested tissues was subsequently done by both electron and light microscope.
Results: In none of the rabbits, any significant change was observed in functional evaluations of outer retina. Histopathologically, an observable decrease in the small type of retinal ganglion cells, vacuolar degeneration of many axons in the inner retina, and also demyelination in the optic nerve were noted. On the other hand, in rabbits given EMB with Zn supplementation, only the outer retina was affected with patches of choroidal depigmentation and damage to the retinal pigment epithelium.
Conclusion: These results suggest that the inner retina and optic nerve were markedly damaged in rabbits with EMB-induced toxic neuroretinopathy. However, those given Zn supplementation were minimally affected by the toxic doses of EMB. Zn may be used as a prophylactic medication to avoid the occurrence of ocular toxicity.

Purpose: To report a case in which a woman developed an optic disc abnormality that was related to breast malignancy.
Case Presentation: A 35-year-old woman presented with a complaint of sudden blurred vision in her right eye（RE）. She had a history of Sjögren syndrome and recurrent dyspnea. Visual acuity in her RE was only slightly reduced, but the visual field defect was prominent. Funduscopy was significant for a blunted optic nerve head margin with surrounding whitish lesion. Autoimmune optic neuropathy was initially suspected due to her history of Sjögren syndrome; therefore, an oral steroid was administered. During subsequent follow-up, the fundus abnormality became more visible and expanded to the retinal background, accompanied by a worsening visual field. Systemic evaluation revealed a breast malignancy, and the patient was diagnosed with malignancy-related optic neuropathy.
Conclusion: Optic nerve abnormality due to malignancy remains among the most challenging diseases in diagnosis. In this case, the patient presented with a history of autoimmune disease and no known oncologic history. Evaluation of such patients should include a comprehensive systemic survey in order to find clues for the etiology, including the possibility of malignancy and metastatic disease.