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Visual Acuity: Clarity or sharpness of Ocular vision or the ability of the eye to see fine details. Visual acuity depends on the functions of Retina, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast.

The Retina

JoVE 10857

The retina is a layer of nervous tissue at the back of the eye that transduces light into neural signals. This process, called phototransduction, is carried out by rod and cone photoreceptor cells in the back of the retina.

Photoreceptors have outer segments with stacks of membranous disks that contain photopigment molecules—such as rhodopsin in rods. The photopigments absorb light, triggering a cascade of molecular events that results in the cell becoming hyperpolarized (with a more negative membrane potential) relative to when it is in the dark. This hyperpolarization decreases neurotransmitter release. Thus, unlike stimuli for most other sensory neurons, light induces a reduction in neurotransmitter release from photoreceptors. Although rods and cones both detect light, they play distinct roles in vision. Rods are highly sensitive to light, and therefore predominate in low-light conditions, such as at night. Cones are less sensitive and are used for most daytime vision. Cones are densely concentrated in the fovea—a small depression near the center of the retina that contains very few rods—and provide a high level of visual acuity in the area where the eye is focused. Cones also convey color information, because the different types—S (short), M (medium), and L (long) in humans—maximally absorb different wa

 Core: Sensory Systems

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…

 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 …

 Emergency Medicine and Critical Care

Cranial Nerves Exam II (VII-XII)

JoVE 10005

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


The cranial nerve examination follows the mental status evaluation in a neurological exam. However, the examination begins with observations made upon greeting…

 Physical Examinations III

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…

 Physical Examinations II

Nonconscious Mimicry Occurs when Affiliation Goals are Present

JoVE 10335

Source: Diego Reinero & Jay Van Bavel—New York University


People are social chameleons and regularly engage in nonconscious behavioral mimicry. This occurs when an individual unwittingly imitates the behaviors of another person, such as crossing one's legs moments after a person sitting adjacent does so, or adjusting one's body…

 Social Psychology

Proper Adjustment of Patient Attire during the Physical Exam

JoVE 10147

Source: Jaideep S. Talwalkar, MD, and Joseph Donroe, MD, Internal Medicine and Pediatrics, Yale School of Medicine, New Haven, CT


In order to optimize the predictive value of the physical examination, the provider must perform maneuvers correctly. The proper use of drapes is an important component of correctly performing…

 Physical Examinations I

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

Vision Training Methods for Sports Concussion Mitigation and Management

1Neurology and Rehabilitative Medicine, University of Cincinnati, 2Division of Sports Medicine, Department of Orthopaedic Surgery, University of Cincinnati, 3Department of Athletics, University of Cincinnati, 4Department of Neurosurgery, University of Cincinnati, 5College of Education, Criminal Justice, and Human Services, University of Cincinnati, 6Division of Sports Medicine, Cincinnati Children's Hospital Medical Center

JoVE 52648

 Behavior

Method Development for Contactless Resonant Cavity Dielectric Spectroscopic Studies of Cellulosic Paper

1Testing and Technical Services, Plant Operations, United States Government Publishing Office, 2Materials Measurement Laboratory, National Institute of Standards and Technology, 3Nanoscale Device Characterization Division, Physical Measurement Laboratory, National Institute of Standards and Technology, 4College of Pharmacy, University of South Florida

JoVE 59991

 Engineering

Development and Implementation of a Multi-Disciplinary Technology Enhanced Care Pathway for Youth and Adults with Concussion

1Department of Biomedical Engineering, Cleveland Clinic Foundation, 2Center for Neurological Restoration, Cleveland Clinic Foundation, 3Office of Clinical Transformation, Cleveland Clinic Foundation, 4Concussion Center, Cleveland Clinic Foundation, 5Neurological Institute Center for Outcomes Research, Cleveland Clinic Foundation, 6Quantitative Health Sciences, Cleveland Clinic Foundation

JoVE 58962

 Medicine

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

JoVE 58571

 Neuroscience

Regenerative Therapy by Suprachoroidal Cell Autograft in Dry Age-related Macular Degeneration: Preliminary In Vivo Report

1Low Vision Research Centre of Milan, 2Department of Ophthalmology, A. Fiorini Hospital, Sapienza University of Rome, 3Glaucoma and Low Vision Study Center, Department of General Surgery and Organ Transplants, University of Bologna, 4Department of Sense Organs, Faculty of Medicine and Odontology, Sapienza University of Rome

JoVE 56469

 Medicine

Corneal Tissue Engineering: An In Vitro Model of the Stromal-nerve Interactions of the Human Cornea

1Department of Cell Biology, University of Oklahoma Health Sciences Center, 2Department of Ophthalmology/Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, 3Department of Physiology, Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center

JoVE 56308

 Developmental Biology

Scanning Light Scattering Profiler (SLPS) Based Methodology to Quantitatively Evaluate Forward and Backward Light Scattering from Intraocular Lenses

1Office of Device Evaluation, Center for Devices and Radiological Health, U.S. Food and Drug Administration, 2Optical Therapeutics and Medical Nanophotonics Laboratory, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration

JoVE 55421

 Engineering

Measurement & Analysis of the Temporal Discrimination Threshold Applied to Cervical Dystonia

1School of Engineering, Trinity College Dublin, The University of Dublin, 2Department of Neurology, St. Vincent's University Hospital, 3School of Medicine and Medical Sciences, University College Dublin, 4School of Mathematical Sciences, Dublin Institute of Technology, 5School of Medicine Trinity College Dublin, The University of Dublin

JoVE 56310

 Neuroscience
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