Optic neuritis is a general term for inflammatory demyelinating disease of the optic nerve. There are two types: papillitis, in which inflammation spreads to the optic nerve papilla and causes optic disc swelling, and retrobulbar neuritis, in which the fundus shows no abnormalities. The optic nerve is composed of axons of retinal ganglion cells (RGCs). Damage to RGC axons or cell bodies caused by optic neuritis present as changes in the retinal thickness of the papilla or macula found with retinal optical coherence tomography (OCT). In the acute phase of optic neuri tis, the circumpapillary retinal nerve fiber layer (cpRNFL) thickness is useful in assessing optic disc swelling. In the chronic phase cpRNFL and inner retinal layer thickness in the macula be come thinner. In addition to the cpRNFL thickness, macular RNFL and the sum of the thickness of ganglion cell layer (GCL) and inner plexiform layer (IPL),”GCL＋IPL”, are useful for under standing the pathophysiology and for follow-up evaluation.

　Nerve fibers from the nasal hemiretina cross behind the optic chiasm and enter the opposite optic tract. However, nerve fibers from the temporal hemiretina enter the ipsilateral optic tract. Consequently, the crossing of the fibers in both eyes results in bilateral temporal hemianopsia as optic chiasm lesions involve the papillomacular bundle and nasolateral nerve fibers. In case of op tic nerve and optic tract lesions, optical coherence tomography (OCT) is performed to measure the circumpapillary retinal nerve fiber layer and macular intraretinal layer thickness. OCT pro vides a detailed assessment of the structure of the optic chiasm and optic tract. Thus, this tech nique can be widely used in the future for further follow-up and prediction of visual field recovery.

　It is widely recognized that patients with homonymous hemianopia secondary to retrogenicu late lesions do not show any funduscopic abnormality and that injury to retinal ganglion cells (RGCs) beyond the synapse at the lateral geniculate nucleus is not observed in these patients. However, technological advances in optical coherence tomography (OCT) have facilitated detec tion of subtle retinal atrophy, and studies in patients with congenital and acquired occipital lobe lesions have reported definitive thinning of the circumpapillary retinal nerve fiber layer (cpRN FL) on OCT in both groups; notably, the degree of cpRNFL thinning was correlated with increas ing time since the injury. Similarly, our findings suggest that degeneration of the RGCs, which corresponds to the homonymous hemianopia, may occur within a few years after posterior cere bral artery (PCA) infarction. In our opinion, our patients with homonymous hemianopia following unilateral PCA infarction showed evidence of trans-synaptic retrograde degeneration (TRD) after an isolated occipital lobe lesion, and the homonymous neuronal loss was detected on OCT based on RGC evaluation. Moreover, area analysis revealed significant thinning in the most central part of the macula, in close proximity to the fovea. During long-term follow-up of the retinal thickness in patients with hemianopia and lesions limited to the posterior pole of the occipital lobe, we did not observe changes immediately after the onset of the brain lesion, and hemianopic thinning of the ganglion cell complex (GCC) became apparent a few years later. Macular GCC and ganglion cell layer ＋ inner plexiform layer thickness measurements provide more valuable information than that provided by cpRNFL measurements to detect the loss of RGCs in patients with TRD in the posterior visual pathway.

　Optical coherence tomography angiography (OCTA) is a minimally invasive procedure that can quantitatively and quickly evaluate stratified blood vessels in the retina, choroid, and optic disc. Advances in OCT imaging technology such as the capacity to increase the scanning speed in OCTA have made it possible to obtain high-resolution images to diagnose retinal vascular dis ease, pachychoroid spectrum disease, and glaucoma; and to evaluate various neuro-ophthalmo logical diseases. Structural changes in the vascular network around the optic disc and the macula have been correlated with functional changes, such as changes in the visual field, in many diseas es. These correlations have been reported in optic nerve diseases such as ischemic optic neuropa thy, optic neuritis, optic disc drusen, compressive optic neuropathy, and hereditary optic neuropa thy; in cerebrovascular diseases including moyamoya disease; and in neurodegenerative diseases including Parkinson's disease. Other aspects of these advances applied in OCTA for diagnostic purposes could be improved, including current limitations of imaging technology and the small sample size of studies on and diagnoses using OCTA alone. To date, new knowledge has been obtained using OCTA. In this presentation, the utilization of OCTA and its role will be discussed using select research reports related to neuro-ophthalmology.

　Ophthalmic practice has undergone substantial transformations since the inception of optical coherence tomography (OCT) approximately three decades previously. In neuro-ophthalmology, the significance of OCT has been especially remarkable in the diagnosis and therapeutic assess ment of optic nerve disorders. Nonetheless, existing OCT techniques can only visualize and quan tify each layer of the retina and cannot directly portray the cellular constituents. Recently, an adaptive optics (AO) technology-equipped experimental OCT (AO-OCT) has acquired high- reso lution retinal images and observed highly reflective entities within the retinal ganglion cell (RGC) layer. These entities are postulated to correspond to the cell bodies of RGCs. Visual impairments associated with optic nerve disorders are closely corrected with the death of RGCs. Consequently, a prospect to gain novel insights in the etiological and progressive mechanisms underlying optic nerve disorders exists by non-invasive evaluation of RGC constituents directly within the human organism through using AO-OCT.

　We report a case of idiopathic intracranial hypertension that was successfully treated with cerebrospinal fluid diversion. A 49-year-old woman was referred to the clinic for headache, photophobia, and temporary visual disturbances when looking down. Our study revealed normal visual acuity and papillary swelling in both eyes. Visual field testing showed mild enlargement of Marriotteʼs blind spots in both eyes. Magnetic resonance imaging showed no space-occupying lesions; however, enlarged subarachnoid space around the optic nerve and tortuosity of the intraorbital optic nerve could be seen, suggesting the presence of intracranial hypertension. She had an intractable headache and was referred to the Department of Neurosurgery, where a lumbar puncture showed a pressure of 35 cmH₂O, she was thus diagnosed with idiopathic intracranial hypertension. Conservative treatment showed no improvement in papilledema and the frequency of temporary visual disturbances. Lumbar abdominal shunt surgery was performed. Postoperatively, her papilledema improved, temporary visual disturbances and photophobia disappeared, headache and ear fullness disappeared, and visual acuity and visual field remained normal. In conservative treatment-resistant cases, timely surgical intervention before irreversible damage to the optic nerve by papilledema is important to preserve visual function.

　A 56-year-old woman diagnosed with normal-tension glaucoma in both eyes had been receiving antiglaucoma treatment for 19 years. She became aware of a pain with eye movement and sud den tunnel vision in the left eye for 4 days and was referred to the Department of Ophthalmology at Hokkaido University Hospital. Her best-corrected visual acuity was 1.2 and 0.8 in the right and left eyes, respectively. The intraocular pressure was 9 mmHg in both eyes. Goldmann visual field testing detected a severe peripheral visual field defect and paracentral scotoma in the left eye and superior nasal step defect in the right eye. Analysis of ganglion cell complex with optical coherence tomography revealed widespread thinning and inferior arcuate thinning in the left and right eyes, respectively. Gadolinium-enhanced magnetic resonance imaging showed enhancement of the left optic nerve and positive serum antiaquaporin-4 (AQP4) antibody, leading to a diagnosis of anti-AQP4 antibody-positive optic neuritis. Two courses of steroid pulse and high-dose intrave nous immunoglobulin therapies were performed, and the left peripheral visual field defect improved. Even in patients with glaucoma, if visual field defects worsen rapidly without intraocular pressure elevation, anti-AQP4 antibody testing should be performed.

　We report a case of Hornerʼs syndrome after herpes zoster infection of the intercostal nerves in which brimonidine tartrate ophthalmic solution improved the ptosis and the anisocoria. A 51-year-old woman developed herpes zoster infection on the right back intercostal area (Th4-6). The dermatologist administered antiherpesvirus drugs, and the rash crusted and healed. Four weeks after the onset, she developed ptosis with left eye miosis and left frontal hypohidrosis, and dysesthesia of the first branch of the left trigeminal nerve appeared. Six weeks after the onset, she was referred to the neurological department and diagnosed with left Hornerʼs syndrome with neuropathy of the first branch of the left trigeminal nerve, and intrathecal herpes zoster infection was suggested. Additional antiherpesviral and steroids therapies did not improve the symptoms, and she presented to our ophthalmological department for left ptosis treatment. Pharmacological testing with phenylephrine hydrochloride showed improvement of the left ptosis and resulted in left eye mydriasis, suggesting that she had peripheral postganglionic Hornerʼs syndrome. A trial of 5% phenylephrine hydrochloride ophthalmic solution was started and the left ptosis improved; however, she complained of photophobia due to mydriasis. After changing to 0.1% brimonidine tartrate, the left ptosis improved without anisocoria. Brimonidine tartrate may be useful as a symptomatic treatment for postganglionic Hornerʼs syndrome.

　A man in his early 40s was referred to our hospital with a complaint of decreased visual acuity in the right eye and orbital pain. He was undergoing treatment for glaucoma with visual field defects, including central areas. Upon initial visit, the right eye visual acuity was 0.07 and a rela tive afferent pupillary defect (RAPD) was detected in the right eye. Dilated fundus exam revealed optic disc swelling in the right eye. Goldmann perimetry showed upper visual field defects and a central scotoma. Brain contrast magnetic resonance imaging (MRI) showed enhanced right optic nerve. As optic neuritis was highly suspected, steroid pulse therapy was administered; however, visual acuity and optic disc swelling remained unchanged after treatment.

　Leber hereditary optic neuropathy (LHON) was suspected and blood tests revealed a m.11778G>A point mutation. After 1 year, the fellow eye showed visual acuity loss without MRI enhancement on the optic nerve; therefore, LHON was diagnosed.

　This report describes a case of LHON that mimics the clinical presentation of optic neuritis due to positive RAPD, orbital pain, and MRI findings.

　LHON should be considered as a differential diagnosis even in cases suspected as optic neuritis due to MRI enhancement.

　We present a patient with cerebrospinal fluid (CSF) leakage with abducens nerve palsy effec tively treated with epidural blood patch (EBP). A 40-year-old woman visited a nearby ophthalmol ogist for an orthostatic headache with nausea and was diagnosed with a migraine. After three weeks, she developed diplopia. Contrast-enhanced magnetic resonance imaging revealed diffuse enlargement of the subdural space and diffuse dural enhancement. She was referred to our hospital for further examination and treatment for suspected CSF leakage including intracranial hypotension syndrome. At the first visit, visual acuity was 1.0 in both eyes, and intraocular pressure was 13 and 15 mmHg in the right and left, respectively. There were no abnormal findings in the anterior segment, optic media, or fundus. Alternate prism cover test (APCT) result was 25 and 16 prism diopter (PD) esotropia at the far distance and near, respectively, and Hess red-green test showed limited abduction in the right eye. Computed tomography myelography revealed CSF leakage, and the patient was diagnosed with abducens nerve palsy due to CSF leakage and intracranial hypotension syndrome. Two weeks after the initial visit, the headache resolved but abducens nerve palsy remained, and EBP was performed one month after the initial visit. After one month of treatment, diplopia had disappeared, the APCT result was 4 PD esophoria at far and near distance, and limited abduction in the right eye had improved. CSF leakage should be considered in patients with abducens nerve palsy with orthostatic headache, and EBP may be useful in the treatment of CSF leakage.

　Omnipause neurons (OPNs) in the nucleus raphe interpositus in the brainstem have tonic ac tivity while our eyes fixate but stop firing before and during saccades. We analyzed synaptic in puts from the rostral and caudal superior colliculi (SCs) to OPNs. The intracellular recording and staining techniques were used to identify the neural substrate for inhibiting OPNs for saccade initiation. OPNs received excitation from the rostral SC and inhibition from the caudal SC. Fur thermore, we demonstrated that the inhibition from the SC to OPNs was mediated by inhibitory burst neurons (IBNs) by sectioning the midline between the bilateral IBNs. These results indicat ed that there is no special supranuclear signal for triggering saccades, but instead, the signal for inhibiting OPNs comes from IBNs of saccadic driving pathways.