DOCSLIB.ORG

The Pupillary Response in Traumatic Brain Injury: a Guide for Trauma Nurses

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Pupillary Response in Traumatic Brain Injury: a Guide for Trauma Nurses CLINICAL CARE The Pupillary Response in Traumatic Brain Injury: A Guide for Trauma Nurses Andrea Adoni, BSN, RN, CCRN, CEN, EMT or stationary object (19%), and assaults (11%).3 Injuries to Molly McNett, PhD(c), MSN, RN the brain are classified as focal, such as cerebral contusions, lacerations, and hematomas/hemorrhages, or diffuse, which include concussions and diffuse axonal injuries.4 Because the signs and symptoms of patients who have sus- ■ ABSTRACT tained TBIs may change quickly and evidence of deteriora- Traumatic brain injuries (TBIs) affect more than 1.4 mil- tion may be subtle, trauma nurses must be adept at lion Americans annually. Trauma nurses caring for these performing astute neurologic assessments. patients routinely perform serial neurologic assessments, A key component of any neurologic assessment is the including pupillary examinations. While trauma nurses pupillary examination.4 Trauma nurses at all levels of are likely familiar with basic components of the pupil- care routinely perform pupillary assessments on patients lary examination, some confusion about more specific and are likely to be familiar with the basic components aspects of the examination and the physiologic basis of of the pupillary examination. However, some confusion the pupillary response may still remain, particularly as it may still remain about more specific aspects of the exam- pertains to patients with TBI. Therefore, the purpose of ination and the physiologic basis of the pupillary this article is to identify the key components of a pupil- response, particularly as it pertains to patients who have lary examination and its associated physiologic sustained TBIs. Therefore, the purpose of this article is to response. A case study is provided to illustrate the appli- identify the key components of the pupillary examina- cation of this information among patients with TBI. tion, explain the physiologic basis of the pupillary response, and illustrate the application of this informa- ■ KEY WORDS tion in patients with TBI through a case study. Brain injury, Pupil, Trauma ■ CASE STUDY raumatic brain injury (TBI) affects more than 1.4 mil- An 18-year-old woman was a restrained driver of a vehi- Tlion Americans annually.1 These injuries, defined as a cle that was T-boned (lateral) at a high speed on the dri- blow or penetrating injury to the head that disrupts normal ver’s side of the car. The car subsequently rolled over onto brain function,2 occur as a result of falls (28%), motor its roof. Emergency medical services arrived to find the vehicle crashes (20%), being struck by or against a moving victim conscious but with a Glasgow Coma Scale (GCS) Score of 13 (Table 1). The victim’s pupils were noted to be equal and reactive. The victim’s level of consciousness continued to deteriorate while the emergency medical Andrea Adoni, BSN, RN, CCRN, CEN, EMT, is Flight Nurse Specialist, Cleveland Metro LifeFlight; MetroHealth Medical services worked to free her from the wreckage. She Center, and ACNP student, Frances Payne Bolton School of arrived at the regional emergency department after Nursing, Case Western Reserve University; and Molly McNett, 40-minute extrication with a GCS Score of 8: she was given MSN, RN, is Research Coordinator, Department of Nursing a 2 for opens eyes to painful stimuli, a 2 for unintelligible Research, MetroHealth Medical Center, Cleveland, Ohio. verbal response, and a 4 for withdraws to pain. Her Corresponding Author: Andrea Adoni, BSN, RN, CCRN, CEN, EMT, Cleveland Metro Lifeflight Office, 4th Floor pupils were now unequal. The right pupil measured 5 mm Hamann, MetroHealth Medical Center, 2500 MetroHealth Dr, and was nonreactive to a direct light, whereas her left Cleveland, OH 44109 ([email protected]). pupil measured 2 mm and displayed a sluggish reaction October–December 2007 Journal of Trauma Nursing • Volume 14, Number 4 191 ■ IDENTIFYING TBI TABLE 1 Identifying an acute brain injury in patients with trauma requires serial neurologic examinations, including pupil- lary assessments, a CT scan, and possibly a magnetic reso- The Glasgow nance imaging. As depicted in the case study, evidence of TBI may be present in the initial neurologic examination Coma Scale performed at the scene. Victims may have altered GCS scores or impaired level of consciousness ranging from sub- Eye opening tle to severe. The initial pupillary examinations may appear Spontaneous 4 benign, and pupillary changes may not surface until hours after the occurrence of the injury. Performing serial neuro- Response to verbal command 3 logic examinations, including pupillary assessments, aids in Response to pain 2 identifying subtle changes in a patient’s neurologic status. No response 1 These subtle changes can indicate the presence of TBI and/or an acute deterioration in a patient’s condition.4 The Best verbal response presence of TBI is confirmed with a CT and/or a magnetic Oriented 5 resonance imaging once a patient arrives in a healthcare facility. The CT scan can quickly aid in differentiating Confused 4 between a focal and a diffuse brain injury. Inappropriate words 3 Subdural hematomas are one type of focal brain injury 4 Incomprehensible sounds 2 occurring in approximately 30% of patients with TBI. An acute subdural hematoma occurs usually after a decelera- No verbal response 1 tion injury in which cerebral veins rupture because of 5 Best motor response either a linear or rotational shearing force. Rupture of these vessels causes bleeding into the subdural space. This Obeys commands 6 bleeding may exert additional pressure onto the surround- Locales to pain 5 ing brain tissue, causing shifting of the tissue or mass effect. Because the subdural space is not limited by the cra- Withdraws to pain 4 nial sutures, this bleeding can potentially spread along the Flexion to pain 3 entire cerebral hemisphere.6 As the size of the bleed and Extension to pain 2 the mass effect on the brain increases, the patient’s neuro- logic status declines, and pupillary changes often appear. No motor response 1 As bleeding continues, the likelihood of a poor prognosis also increases: mortality rates as high as 50% have been reported among the patients who present with a subdural hematoma requiring immediate surgical evacuation.6 to direct light. She was noted to have a small forehead laceration with surrounding ecchymosis. She was ■ THE PUPILLARY EXAMINATION sedated, paralyzed, and intubated by the emergency The standard of care for any patient with TBI includes department staff to ensure airway protection. A comput- serial neurologic examinations. These examinations erized tomography (CT) scan of the patient’s head was include a pupillary assessment and are often performed performed, which revealed a large subdural hematoma. by trauma nurses at the scene, in the emergency depart- The patient’s neurologic status continued to deteriorate, ment, and in the acute and critical care units.7 Unlike and, therefore, the local air medical service was immedi- other components of the neurologic examination that ately dispatched to transport the patient to a level I require patients to be conscious, the pupillary examina- trauma center. She was transported to a level I trauma tion is one of the few neurologic signs that can be center for further evaluation of her head injury. Upon her assessed in an unconscious patient or in a patient receiv- arrival to the trauma center, her trauma evaluation was ing neuromuscular blocking agents and sedation. The completed, and she was transferred to the surgical inten- pupillary examination is a minimally invasive assessment, sive care unit. Her pupils were found nonreactive on her which provides valuable information about the severity initial trauma evaluation at the trauma center. In the sur- and progression of the brain injury, as well as brainstem gical intensive care unit, a neurosurgical consultation for function. Thus, it is important for trauma nurses to per- the treatment of an acute subdural hematoma and possi- form pupillary examinations thoroughly and understand ble surgical evacuation was obtained. the physiologic basis of the pupillary response. 192 Journal of Trauma Nursing • Volume 14, Number 4 October–December 2007 When performing a pupillary examination in patients A complete pupillary reactivity examination also with TBI, a trauma nurse should make the conscious includes assessment of the consensual pupillary response patient focus on a distant object straight ahead. In the and accommodation. The consensual pupillary response comatose patient, pupils are assessed per the position is the constriction that normally occurs in a pupil when they are found in. A pupil assessment should include the light is shown into the opposite eye.6 Because of this examination of size and equality of pupils, pupillary response, the trauma nurse should wait for several sec- shape, and reactivity to light. onds before assessing pupillary light reflex in the second eye, as that pupil may be temporarily constricted. Pupil Size and Equality Accommodation is the constriction of pupils that occurs Pupil size is reported as the width or diameter of each when a conscious patient is focusing on a close object. pupil in millimeters. A standardized pupil gauge should Pupils should normally constrict bilaterally when an be used to report the pupil size in millimeters. The use of object is held within 4 to 6 inches of a patient’s nose.6 this gauge aids in decreasing subjectivity, particularly when serial assessments are performed. The normal ■
Load more

Recommended publications
  • Symptoms of Age Related Macular Degeneration
    WHAT IS MACULAR DEGENERATION? wavy or crooked, visual distortions, doorway and the choroid are interrupted causing waste or street signs seem bowed, or objects may deposits to form. Lacking proper nutrients, the light- Age related macular degeneration (AMD) is appear smaller or farther away than they sensitive cells of the macula become damaged. a disease that may either suddenly or gradually should, decrease in or loss of central vision, and The damaged cells can no longer send normal destroy the macula’s ability to maintain sharp, a central blurry spot. signals from the macula through the optic nerve to central vision. Interestingly, one’s peripheral or DRY: Progression with dry AMD is typically slower your brain, and consequently your vision becomes side vision remains unaffected. AMD is the leading de-gradation of central vision: need for increasingly blurred cause of “legal blindness” in the United States for bright illumination for reading or near work, diffi culty In either form of AMD, your vision may remain fi ne persons over 65 years of age. AMD is present in adapting to low levels of illumination, worsening blur in one eye up to several years even while the other approximately 10 percent of the population over of printed words, decreased intensity or brightness of eye’s vision has degraded. Most patients don’t the age of 52 and in up to 33 percent of individuals colors, diffi culty recognizing faces, gradual increase realize that one eye’s vision has been severely older than 75. The macula allows alone gives us the in the haziness of overall vision, and a profound drop reduced because your brain compensates the bad ability to have: sharp vision, clear vision, color vision, in your central vision acuity.
    [Show full text]
  • How Clean Is Your Capsule?
    Eye (1989) 3, 678-684 How Clean is Your Capsule? W. T. GREEN and D. L. BOASE Portsmouth Summary Proliferation of residual lens epithelial cells is believed to be the major cause of pos­ terior capsule opacification following extracapsular cataract extraction. During sur­ gery these cells can be visualised with appropriate illumination facilitating their mechanical removal with the McIntyre cannula. When flat preparations of the anterior capsule are examined by light microscopy, the areas 'cleaned' of cells in this way appear transparent but scanning electron microscopy reveals tufts of remaining debris which may represent points of cellular attachment to the capsule. Control of lens epithelial cell proliferation is important for the future development of cataract surgery. The undoubted advantages of extracapsular and also on human cadaver eyes. A horizontal cataract extraction are offset in many patients capsulotomy in the upper part of the lens by posterior capsule opacification requiring allowed nucleus removal. Irrigation and caps ulotomy. Not only is this disappointing aspiration of the cortical lens material was for the patient, but the procedure carries a then carried out using a McIntyre cannula risk of serious complications. with Hartman's irrigation solution. During in The major cause of posterior capsule opac­ vitro surgery this was aided by first removing ification is proliferation of residual lens epi­ the entire cornea and iris to improve visual­ thelial cells. I If these cells could be removed at isation and explore different methods of the time of surgery we believe that the inci­ illumination. dence of posterior capsule opacification and The importance of illumination was first the need for subsequent capsulotomy would suspected when it was observed, during rou­ be reduced.
    [Show full text]
  • Accommodation in the Holmes-Adie Syndrome by G
    J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.21.4.290 on 1 November 1958. Downloaded from J. Neurol. Neurosurg. Psychiat., 1958, 21, 290. ACCOMMODATION IN THE HOLMES-ADIE SYNDROME BY G. F. M. RUSSELL From the Neurological Research Unit, the National Hospital, Queen Square, London In 1936, Bramwell suggested that the title response to near and far vision respectively. But it "Holmes-Adie syndrome" be given to the clinical has also been noted that the reaction to convergence complex of a slowly reacting pupil and absent tendon may be remarkably wide in its range, considering reflexes in recognition of the descriptions by Holmes that it often follows a stage of complete paralysis (1931) and Adie (1932). Both authors had empha- (Strasburger, 1902). Not only is the reaction to sized the chief clinical features-dilatation of the convergence well preserved when compared to the pupil, apparent loss of the reaction to light, slow reaction to light, but it may in fact be excessive constriction and relaxation in response to near and (Alajouanine and Morax, 1938; Heersema and distant vision, and partial loss of the tendon reflexes. Moersch, 1939). In assessing the degree of tonicity Although the syndrome had been recognized wholly there are, therefore, two criteria: slowness ofguest. Protected by copyright. or in part many years previously (Strasburger, 1902; pupillary movement and preservation of the range Saenger, 1902; Nonne, 1902; Markus, 1906; Weill of movement. and Reys, 1926), credit must go to Adie for stressing Adler and Scheie (1940) showed that the tonic the benign nature of the disorder and distinguishing pupil constricts after the conjunctival instillation it clearly from neurosyphilis.
    [Show full text]
  • Selective Attention Within the Foveola
    ARTICLES Selective attention within the foveola Martina Poletti1 , Michele Rucci1,2 & Marisa Carrasco3,4 Efficient control of attentional resources and high-acuity vision are both fundamental for survival. Shifts in visual attention are known to covertly enhance processing at locations away from the center of gaze, where visual resolution is low. It is unknown, however, whether selective spatial attention operates where the observer is already looking—that is, within the high-acuity foveola, the small yet disproportionally important rod-free region of the retina. Using new methods for precisely controlling retinal stimulation, here we show that covert attention flexibly improves and speeds up both detection and discrimination at loci only a fraction of a degree apart within the foveola. These findings reveal a surprisingly precise control of attention and its involvement in fine spatial vision. They show that the commonly studied covert shifts of attention away from the fovea are the expression of a global mechanism that exerts its action across the entire visual field. Covert attention is essential for visual perception. Among its many previous studies. We then investigated the consequences of attention advantages, covert allocation of attentional resources increases con- for both detection (experiment 2) and discrimination (experiments trast sensitivity and spatial resolution, speeds information accrual and 3 and 4) tasks within the foveola. reaction times1–4, and alters the signal at the target location during saccade preparation5–7. Covert attention has been studied sometimes RESULTS in the parafovea (1°–5°) and mostly in the perifovea (5°–10°) and Experiment 1 consisted of a central spatial cueing task with para- periphery (>10° of eccentricity)—that is, far outside the foveola, the foveal stimuli (Fig.
    [Show full text]
  • Cranial Nerve Palsy
    Cranial Nerve Palsy What is a cranial nerve? Cranial nerves are nerves that lead directly from the brain to parts of our head, face, and trunk. There are 12 pairs of cranial nerves and some are involved in special senses (sight, smell, hearing, taste, feeling) while others control muscles and glands. Which cranial nerves pertain to the eyes? The second cranial nerve is called the optic nerve. It sends visual information from the eye to the brain. The third cranial nerve is called the oculomotor nerve. It is involved with eye movement, eyelid movement, and the function of the pupil and lens inside the eye. The fourth cranial nerve is called the trochlear nerve and the sixth cranial nerve is called the abducens nerve. They each innervate an eye muscle involved in eye movement. The fifth cranial nerve is called the trigeminal nerve. It provides facial touch sensation (including sensation on the eye). What is a cranial nerve palsy? A palsy is a lack of function of a nerve. A cranial nerve palsy may cause a complete or partial weakness or paralysis of the areas served by the affected nerve. In the case of a cranial nerve that has multiple functions (such as the oculomotor nerve), it is possible for a palsy to affect all of the various functions or only some of the functions of that nerve. What are some causes of a cranial nerve palsy? A cranial nerve palsy can occur due to a variety of causes. It can be congenital (present at birth), traumatic, or due to blood vessel disease (hypertension, diabetes, strokes, aneurysms, etc).
    [Show full text]
  • Taking the Mystery out of Abnormal Pupils
    Taking the mystery out of abnormal pupils No financial disclosures Course Title: Taking the mystery out [email protected] of abnormal pupils Lecturer: Brad Sutton, OD, FAAO Clinical Professor IU School of Optometry . •Review of Anatomy Iris anatomy Iris sphincter Iris dilator Parasympathetic pathway Sympathetic pathway Parasympathetic Pathway Parasympathetic Pathway Light stimulates the retina then impulse Four neuron arc travels with the ganglion cells through the Retina to the pretectal nucleus in the chiasm into the optic tracts. 80% go to the midbrain (1) LGN , 20% to the pretectal nuclei.They Pretectal nucleus to the EW nucleus (2) then hemidecussate and terminate at the EW nucleus EW nucleus to the ciliary ganglion (3) Ciliary ganglion to the iris sphincter with short ciliary nerves (4) 1 Points of Interest Sympathetic Pathway Within the second order neuron there are Three neuron arc 30 near response fibers for every light Posterior hypothalamus to ciliospinal response fiber. This allows for light - near center of Budge ( C8 - T2 ). (1) dissociation. Center of Budge to the superior cervical The third order neuron runs with cranial ganglion in the neck (2) nerve III from the brain stem to the ciliary Superior cervical ganglion to the dilator ganglion. Superficially located prior to the muscle (3) cavernous sinus. Points of Interest Second order neuron runs along the surface of the lung, can be affected by a Pancoast tumor Third order neuron runs with the carotid artery then with the ophthalmic division of cranial nerve V 2 APD Testing testing……………….AKA……… … APD / reverse APD Direct and consensual response Which is the abnormal pupil ? Very simple rule.
    [Show full text]
  • Retinal Ganglion Cell Loss Is Size Dependent in Experimental Glaucoma
    Investigative Ophthalmology & Visual Science, Vol. 32, No. 3, March 1991 Copyright © Association for Research in Vision and Ophthalmology Retinal Ganglion Cell Loss Is Size Dependent in Experimental Glaucoma Yoseph Glovinsky,* Harry A. Quigley,f and Gregory R. Dunkelbergerf Thirty-two areas located in the temporal midperipheral retina were evaluated in whole-mount prepara- tions from four monkeys with monocular experimental glaucoma. Diameter frequency distributions of remaining ganglion cells in the glaucomatous eye were compared with corresponding areas in the normal fellow eye. Large cells were significantly more vulnerable at each stage of cell damage as determined by linear-regression analysis. The magnitude of size-dependent loss was moderate at an early stage (20% loss), peaked at 50% total cell loss, and decreased in advanced damage (70% loss). In glaucomatous eyes, the lower retina had significantly more large cell loss than the corresponding areas of the upper retina. In optic nerve zones that matched the retinal areas studied, large axons selectively were damaged first. Psychophysical testing aimed at functions subserved by larger ganglion cells is recommended for detection and follow-up of early glaucoma; however, assessment of functions unique to small cells is more appropriate for detecting change in advanced glaucoma. Invest Ophthalmol Vis Sci 32:484-491, 1991 Current psychophysical tests do not detect glau- tage of ideal cellular preservation. Eyes with mild, comatous damage until a substantial minority of reti- moderate, and late damage were evaluated. In addi- nal ganglion cells have died.1'2 To develop more sen- tion, we correlated the damage patterns in the retinas sitive tests, a comprehensive understanding of the and optic nerves of the glaucomatous eyes.
    [Show full text]
  • The Pupillary Light Reflex in the Critically Ill Patient
    light must be high for the iris to be seen, which reduces Editorials the step increase induced by the penlight).6 If the pupillary light reflex amplitude is less than 0.3 mm and the maximum constriction velocity is less than 1 mm/s, the reflex is unable to be detected using a The pupillary light reflex in penlight.6 In conscious patients with Holmes-Adie and Argyll-Robertson pupils with ‘absent’ pupillary light the critically ill patient reflexes, small light reflexes have been detected using infrared pupillometry.7 Also in post-resuscitation non- brain dead critically ill patients with ‘absent’ pupillary The pupillary response to light is controlled by the reflexes, the reflex has been demonstrated using a autonomic nervous system. The direct pupillary light portable infrared pupillometer.6 reflex refers to miosis that occurs in the stimulated eye; In this issue of Critical Care and Resuscitation, the consensual pupillary light reflex refers to miosis that Thomas8 describes a case of Guillain Barré syndrome occurs in the other eye. The reflex has a latent period presenting with weakness and fixed dilated pupils who with length of the period, amplitude of the response, and subsequently became ‘locked in’ with absence of any the speed of the pupillary constriction dependent on the clinical response to external stimuli. A positive brain intensity of the stimulus employed.1 For the reflex to be stem auditory evoked response was used to indicate truly tested, an intense stimulus and close observation normal brain stem function. In another recent report, a are required. The reflex has afferent, efferent and central case of ‘reversible fixed dilated pupils’ was associated connections; therefore non-response to light (i.e.
    [Show full text]
  • What's the Connection?
    WHAT’S THE CONNECTION? Sharon Winter Lake Washington High School Directions for Teachers 12033 NE 80th Street Kirkland, WA 98033 SYNOPSIS Students elicit and observe reflex responses and distinguish between types STUDENT PRIOR KNOWL- of reflexes. They then design and conduct experiments to learn more about EDGE reflexes and their control by the nervous system. Before participating in this LEVEL activity students should be able to: Exploration, Concept/Term Introduction Phases ■ Describe the parts of a Application Phase neuron and explain their functions. ■ Distinguish between sensory and motor neurons. Getting Ready ■ Describe briefly the See sidebars for additional information regarding preparation of this lab. organization of the nervous system. Directions for Setting Up the Lab General: INTEGRATION Into the Biology Curriculum ■ Make an “X” on the chalkboard for the teacher-led introduction. ■ Health ■ Photocopy the Directions for Students pages. ■ Biology I, II ■ Human Anatomy and Teacher Background Physiology A reflex is an involuntary neural response to a specific sensory stimulus ■ AP Biology that threatens the survival or homeostatic state of an organism. Reflexes Across the Curriculum exist in the most primitive of species, usually with a protective function for ■ Mathematics animals when they encounter external and internal stimuli. A primitive ■ Physics ■ example of this protective reflex is the gill withdrawal reflex of the sea slug Psychology Aplysia. In humans and other vertebrates, protective reflexes have been OBJECTIVES maintained and expanded in number. Examples are the gag reflex that At the end of this activity, occurs when objects touch the sides students will be able to: or the back of the throat, and the carotid sinus reflex that restores blood ■ Identify common reflexes pressure to normal when baroreceptors detect an increase in blood pressure.
    [Show full text]
  • A Model of Accommodative-Pupillary Dynamics Stanley Gordon Day Iowa State University
    Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1969 A model of accommodative-pupillary dynamics Stanley Gordon Day Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Electrical and Electronics Commons Recommended Citation Day, Stanley Gordon, "A model of accommodative-pupillary dynamics " (1969). Retrospective Theses and Dissertations. 4649. https://lib.dr.iastate.edu/rtd/4649 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. This dissertation has been microâhned exactly as received 69-15,607 DAY, Stanley Gordon, 1939- A MODEL OF ACCOMMODATIVE-PUPILLARY DYNAMICS. Iowa State University, Ph.D., 1969 Engineering, electrical University Microfilms, Inc., Ann Arbor, Michigan ®Copyright by STANLEY GORDON DAY 1969 A MODEL OF ACCOMMODATIVE-PUPILLARY DYNAMICS by Stanley Gordon Day A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF PHILOSOPHY Major Subject : Electrical Engineering Approved: Signature was redacted for privacy. In Charge of Major Work Signature was redacted for privacy. Head of Major Department Signature was redacted for privacy. Dea^ of Gradulate College Iowa State University Of Science and Technology Ames, Iowa 1969 il TABLE OF CONTENTS Page DEDICATION iii INTRODUCTION 1 REVIEW OF LITERATURE 4 EQUIPMENT AND METHODS 22 RESULTS AND DISCUSSION 47 SUÎ4MARY AND CONCLUSIONS 60 BIBLIOGRAPHY 62 ACKNOWLEDGEMENTS 68 APPENDIX 69 i iii DEDICATION This dissertation is dedicated to Sandra R.
    [Show full text]
  • Asymmetries of Dark and Bright Negative Afterimages Are Paralleled by Subcortical on and OFF Poststimulus Responses
    1984 • The Journal of Neuroscience, February 22, 2017 • 37(8):1984–1996 Systems/Circuits Asymmetries of Dark and Bright Negative Afterimages Are Paralleled by Subcortical ON and OFF Poststimulus Responses X Hui Li,1,2 X Xu Liu,1,2 X Ian M. Andolina,1 Xiaohong Li,1 Yiliang Lu,1 Lothar Spillmann,3 and Wei Wang1 1Institute of Neuroscience, State Key Laboratory of Neuroscience, Key Laboratory of Primate Neurobiology, Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China, 2University of Chinese Academy of Sciences, Shanghai 200031, China, and 3Department of Neurology, University of Freiburg, 79085 Freiburg, Germany Humans are more sensitive to luminance decrements than increments, as evidenced by lower thresholds and shorter latencies for dark stimuli. This asymmetry is consistent with results of neurophysiological recordings in dorsal lateral geniculate nucleus (dLGN) and primary visual cortex (V1) of cat and monkey. Specifically, V1 population responses demonstrate that darks elicit higher levels of activation than brights, and the latency of OFF responses in dLGN and V1 is shorter than that of ON responses. The removal of a dark or bright disc often generates the perception of a negative afterimage, and here we ask whether there also exist asymmetries for negative afterimages elicited by dark and bright discs. If so, do the poststimulus responses of subcortical ON and OFF cells parallel such afterimage asymmetries? To test these hypotheses, we performed psychophysical experiments in humans and single-cell/S-potential recordings in cat dLGN. Psychophysically, we found that bright afterimages elicited by luminance decrements are stronger and last longer than dark afterimages elicited by luminance increments of equal sizes.
    [Show full text]
  • Miotics in Closed-Angle Glaucoma
    Brit. J. Ophthal. (I975) 59, 205 Br J Ophthalmol: first published as 10.1136/bjo.59.4.205 on 1 April 1975. Downloaded from Miotics in closed-angle glaucoma F. GANIAS AND R. MAPSTONE St. Paul's Eye Hospital, Liverpool The initial treatment of acute primary closed-angle Table i Dosage in Groups I, 2, and 3 glaucoma (CAG) is directed towards lowering intraocular pressure (IOP) to normal levels as Group Case no. Duration IOP Time rapidly as possible. To this end, aqueous inflow is (days) (mm. Hg) (hrs) reduced by a drug such as acetazolamide (Diamox), and aqueous outflow is increased via the trabecular I I 2 8 5 meshwork by opening the closed angle with miotics. 3 7 21 3 The use of miotics is of respectable lineage and hal- 5 '4 48 7 lowed by usage, but regimes vary from "intensive" 7 8 I4 5 9 I0 I8 6 (i.e. frequent) to "occasional" (i.e. infrequent) instilla- I I 2 12 6 tions. Finally, osmotic agents are used after a variable '3 5 20 6 interval of time if the IOP remains raised. Tlle pur- I5 '4 I8 6 pose of this paper is to investigate the value of '7 '4 i6 6 miotics in the initial treatment of CAG. I9 6 02 2 2 2 8 2I 5 Material and methods 4 20t 20 6 Twenty patients with acute primary closed-angle glau- 6 I i8 5 http://bjo.bmj.com/ coma were treated, alternately, in one of two ways 8 4 i8 5 detailed below: I0 6 I8 6 I2 I0 20 6 (I) Intravenous Diamox 500 mg.
    [Show full text]