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Optic Nerve: The 2nd cranial nerve. The optic nerve conveys visual information from the retina to the brain. The nerve carries the axons of the retinal ganglion cells which sort at the optic chiasm and continue via the optic tracts to the brain. The largest projection is to the lateral geniculate nuclei; other important targets include the superior colliculi and the suprachiasmatic nuclei. Though known as the second cranial nerve, it is considered part of the central nervous system.

Ophthalmoscopic Examination

JoVE 10146

Source: Richard Glickman-Simon, MD, Assistant Professor, Department of Public Health and Community Medicine, Tufts University School of Medicine, MA

The simplest ophthalmoscopes consist of an aperture to look through, a diopter indicator, and a disc for selecting lenses. The ophthalmoscope is primarily used to examine the fundus, or the inner wall of the posterior eye, which consists of the choroid, retina, fovea, macula, optic disc, and retinal vessels (Figure 1). The spherical eyeball collects and focuses light on the neurosensory cells of the retina. Light is refracted as it passes sequentially through the cornea, the lens, and the vitreous body. The first landmark observed during the funduscopic exam is the optic disc, which is where the optic nerve and retinal vessels enter the back of the eye (Figure 2). The disc usually contains a central whitish physiologic cup where the vessels enter; it normally occupies less than half the diameter of the entire disc. Just lateral and slightly inferior is the fovea, a darkened circular area that demarcates the point of central vision. Around this is the macula. A blind spot approximately 15° temporal to the line of gaze results from a lack of photoreceptor cells at the optic disc.

Cranial Nerves Exam I (I-VI)

JoVE 10091

Source:Tracey A. Milligan, MD; Tamara B. Kaplan, MD; Neurology, Brigham and Women's/Massachusetts General Hospital, Boston, Massachusetts, USA

During each section of the neurological testing, the examiner uses the powers of observation to assess the patient. In some cases, cranial nerve dysfunction is readily apparent: a patient might mention a characteristic chief complaint (such as loss of smell or diplopia), or a visually evident physical sign of cranial nerve involvement, such as in facial nerve palsy. However, in many cases a patient's history doesn't directly suggest cranial nerve pathologies, as some of them (such as sixth nerve palsy) may have subtle manifestations and can only be uncovered by a careful neurological exam. Importantly, a variety of pathological conditions that are associated with alterations in mental status (such as some neurodegenerative disorders or brain lesions) can also cause cranial nerve dysfunction; therefore, any abnormal findings during a mental status exam should prompt a careful and complete neurological exam. The cranial nerve examination is applied neuroanatomy. The cranial nerves are symmetrical; therefore, while performing the examination, the examiner should compare each side to the other. A physician should approach the examination in a


 Physical Examinations III

Lateral Canthotomy and Inferior Cantholysis

JoVE 10266

Source: James W Bonz, MD, Emergency Medicine, Yale School of Medicine, New Haven, Connecticut, USA

Lateral canthotomy is a potentially eyesight-saving procedure when performed emergently for an orbital compartment syndrome. An orbital compartment syndrome results from a buildup of pressure behind the eye; as pressure mounts, both the optic nerve and its vascular supply are compressed, rapidly leading to nerve damage and blindness if the pressure is not quickly relieved. The medial and lateral canthal tendons hold the eyelids firmly in place forming an anatomical compartment with limited space for the globe. In an orbital compartment syndrome, pressure rapidly increases as the globe is forced against the eyelids. Lateral canthotomy is the procedure by which the lateral canthal tendon is severed, thereby releasing the globe from its fixed position. Often, severing of the lateral canthal tendon alone is not enough to release the globe and the inferior portion (inferior crus) of the lateral canthal tendon also needs to be severed (inferior cantholysis). This increases precious space behind the eye by allowing the globe to become more proptotic, resulting in decompression. Most frequently, orbital compartment syndrome is the result of acute facial trauma, with the subsequent development of a retrobulbar


 Emergency Medicine and Critical Care

Finding Your Blind Spot and Perceptual Filling-in

JoVE 10195

Source: Laboratory of Jonathan Flombaum—Johns Hopkins University

In the back of everyone's eye is a small piece of neural tissue called the retina. The retina has photosensitive cells that respond to stimulation by light. The responses of these cells are sent into the brain through the optic nerve, a bundle of neural fibers. In each retina there is a place somewhere in the periphery where the outputs from retinal cells collect and the bundled optic nerve exits to the brain. At that location, there is no photosensitivity-whatever light reflects from the world and lands in that position does not produce a signal in the brain. As a result, humans have a blind spot, a place in the visual field for which they don't process incoming stimuli. However, people are not aware that they have blind spots; there is not an empty hole in the visual images in front of the eyes. So what do people see in their blind spots? The brain actually fills-in missing input based on the surroundings. This video demonstrates how to find a person's blind spot, and how to investigate the mechanisms of perceptual filling-in.


 Sensation and Perception

Eye Exam

JoVE 10149

Source: Richard Glickman-Simon, MD, Assistant Professor, Department of Public Health and Community Medicine, Tufts University School of Medicine, MA

Proper evaluation of the eyes in a general practice setting involves vision testing, orbit inspection, and ophthalmoscopic examination. Before beginning the exam, it is crucial to be familiar with the anatomy and physiology of the eye. The upper eyelid should be slightly over the iris, but it shouldn't cover the pupil when open; the lower lid lies below the iris. The sclera normally appears white or slightly buff in color. The appearance of conjunctiva, a transparent membrane covering the anterior sclera and the inner eyelids, is a sensitive indicator of ocular disorders, such as infections and inflammation. The tear-producing lacrimal gland lies above and lateral to the eyeball. Tears spread down and across the eye to drain medially into two lacrimal puncta before passing into the lacrimal sac and nasolacrimal duct to the nose. The iris divides the anterior from the posterior chamber. Muscles of the iris control the size of the pupil, and muscles of the ciliary body behind it control the focal length of the lens. The ciliary body also produces aqueous humor, which largely determines intraocular pressure (Figure 1). Cranial nerve


 Physical Examinations II

Murine In Utero Electroporation

JoVE 5208

In utero electroporation is an important technique for studying the molecular mechanisms that guide the proliferation, differentiation, migration, and maturation of cells during neural development. Electroporation enables the rapid and targeted delivery of material into cells by utilizing electrical pulses to create transient pores in cell membranes. Although electroporation has traditionally been used in in vitro studies, scientific advancements have now broadened its utilization to intact organs, such as those found in mouse embryos developing in utero. This video will introduce the key principles behind in utero electroporation in addition to reviewing the basic surgical techniques required to access developing embryos within a pregnant rodent. Details of the injection and electroporation steps are provided along with important considerations for directing gene delivery to specific brain regions. Finally, neurobiological applications of in utero electroporation are presented, such as investigating how specific genes contribute to neural development and how connections form between developing neurons.


 Neuroscience

Induction of Paralysis and Visual System Injury in Mice by T Cells Specific for Neuromyelitis Optica Autoantigen Aquaporin-4

1Department of Neurology, University of California, 2Program in Immunology, University of California, 3Department of Neurology and Neurological Sciences, Stanford University, 4Department of Pathology, Stanford University

JoVE 56185


 Immunology and Infection

Using Retinal Imaging to Study Dementia

1Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, 2Department of Medicine & Therapeutics, The Chinese University of Hong Kong, 3Therese Pei Fong Chow Research Centre for Prevention of Dementia, The Chinese University of Hong Kong, 4Gerald Choa Neuroscience Centre, The Chinese University of Hong Kong, 5Memory Aging and Cognition Centre, National University Health System, 6Department of Pharmacology, National University of Singapore, 7Singapore Eye Research Institute, Singapore National Eye Centre, 8Duke-NUS Medical School, National University of Singapore

JoVE 56137


 Medicine

Isolation of Primary Murine Retinal Ganglion Cells (RGCs) by Flow Cytometry

1Department of Ophthalmology, Hamilton Eye Institute, University of Tennessee Health Science Center, 2Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, 3Department of Anatomy and Neurobiology, University of Tennessee Health Science Center, 4Department of Pharmaceutical Sciences, University of Tennessee Health Science Center

JoVE 55785


 Bioengineering

Ultrahigh Resolution Mouse Optical Coherence Tomography to Aid Intraocular Injection in Retinal Gene Therapy Research

1Research Service, VA Western New York Healthcare System, 2Department of Ophthalmology, (Ross Eye Institute), Jacobs School of Medicine and Biomedical Sciences, University at Buffalo- SUNY, 3Pharmacology/Toxicology, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo- SUNY, 4Physiology/Biophysics, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo- SUNY, 5Neuroscience Program, Jacobs School of Medicine and Biomedical Sciences, University at Buffalo- SUNY, 6The RNA Institute, University at Buffalo- SUNY, 7The SUNY Eye Institute

Video Coming Soon

JoVE 55894


 JoVE In-Press

Laser Capture Microdissection of Highly Pure Trabecular Meshwork from Mouse Eyes for Gene Expression Analysis

1Immunity, Inflammation, and Disease Laboratory, Division of Intramural Research, National Institute of Environmental Health Sciences, NIH, 2Cellular and Molecular Pathology Branch, Division of the National Toxicology Program, National Institute of Environmental Health Sciences, NIH, 3Integrated Laboratory Systems Inc., 4Experimental Pathology Laboratories Inc.

JoVE 57576


 Biology

Use of Rabbit Eyes in Pharmacokinetic Studies of Intraocular Drugs

1Department of Ophthalmology, Seoul National University Bundang Hospital, 2Department of Ophthalmology, College of Medicine, Seoul National University, 3Department of Ophthalmology, Hanyang University Hospital, 4Department of Ophthalmology, Seoul Metropolitan Government-Seoul National University Boramae Medical Center, 5Department of Clinical Pharmacology, Seoul National University Hospital, 6Department of Clinical Pharmacology, Seoul National University Bundang Hospital

JoVE 53878


 Medicine

Imaging Ca2+ Dynamics in Cone Photoreceptor Axon Terminals of the Mouse Retina

1Institute for Ophthalmic Research, University of Tübingen, 2Graduate School of Cellular & Molecular Neuroscience, University of Tübingen, 3Bernstein Centre for Computational Neuroscience, University of Tübingen, 4Molecular Genetics Laboratory, University of Tübingen, 5Centre for Ophthalmology, University of Tübingen

JoVE 52588


 Neuroscience

Blood Withdrawal I

JoVE 10246

Source: Kay Stewart, RVT, RLATG, CMAR; Valerie A. Schroeder, RVT, RLATG. University of Notre Dame, IN

Blood collection is a common requirement for research studies that involve mice and rats. The method of blood withdrawal in mice and rats is dependent upon the volume of blood needed, the frequency of the sampling, the health status of the animal to be bled, and the skill level of the technician.1 All methods discussed-retro-orbital sinus bleeds, initial tail snip bleeds, and intracardiac bleeds-require the use of a general anesthesia.


 Lab Animal Research

Isolation of Retinal Arterioles for Ex Vivo Cell Physiology Studies

1Centre for Experimental Medicine, Queen's University of Belfast, 2Centre for Biomedical Sciences (Education), Queen's University of Belfast, 3Department of Pharmaceutical Chemistry and Pharmacognosy, Naresuan University, 4School of Medicine, Dentistry and Biomedical Sciences, Queen's University of Belfast

JoVE 57944


 Biology

Derivation of Glial Restricted Precursors from E13 mice

1Hugo W. Moser Research Institute at Kennedy Krieger, Johns Hopkins University, 2Department of Neurology, Johns Hopkins School of Medicine, 3University of Maryland, 4Experimental Neurology, Biogen Idec, 5The Brain Science Institute, Johns Hopkins School of Medicine, 6Department of Pediatrics, Johns Hopkins School of Medicine

JoVE 3462


 Neuroscience

Measurement of Energy Metabolism in Explanted Retinal Tissue Using Extracellular Flux Analysis

1Division of Metabolism, Endocrinology and Lipid Research, Department of Medicine, Washington University School of Medicine, 2Department of Biomedical Engineering, Washington University in Saint Louis, 3Department of Ophthalmology and Visual Science, Washington University School of Medicine

Video Coming Soon

JoVE 58626


 JoVE In-Press

Using Optical Coherence Tomography and Optokinetic Response As Structural and Functional Visual System Readouts in Mice and Rats

1Department of Neurology, Heinrich-Heine-University Düsseldorf, 2Department of Cell Physiology, Faculty of Biology and Biotechnology, Ruhr-University Bochum, 3Division of Neuroinflammation and Glial Biology, Department of Neurology, University of California San Francisco

Video Coming Soon

JoVE 58571


 JoVE In-Press

A Metadata Extraction Approach for Clinical Case Reports to Enable Advanced Understanding of Biomedical Concepts

1The NIH BD2K Center of Excellence in Biomedical Computing, University of California, Los Angeles, 2Department of Physiology, University of California, Los Angeles, 3Department of Medicine/Cardiology, University of California, Los Angeles, 4Department of Cardiology, First Affiliated Hospital, Zhejiang University School of Medicine, 5Department of Radiological Sciences, University of California, Los Angeles, 6Department of Bioengineering, University of California, Los Angeles, 7Scalable Analytics Institute (ScAi), University of California, Los Angeles, 8Department of Bioinformatics, University of California, Los Angeles, 9Department of Computer Science, University of California, Los Angeles

JoVE 58392


 Medicine

Novel Photoacoustic Microscopy and Optical Coherence Tomography Dual-modality Chorioretinal Imaging in Living Rabbit Eyes

1Kellogg Eye Center, Department of Ophthalmology and Visual Sciences, University of Michigan, 2Department of Biomedical Engineering, University of Michigan, 3Institute of Biomedical Engineering, Chinese Academy of Medical Sciences & Peking Union Medical College, 4Department of Radiology, University of Michigan

JoVE 57135


 Engineering

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