DOCSLIB.ORG

Unilateral Light-Near Dissociation in Lesions of the Rostral Midbrain

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Unilateral Light-Near Dissociation in Lesions of the Rostral Midbrain SMALL CASE SERIES Report of Cases. Case 1. A 19-year- pupil (eg, irregular shape, sector Unilateral Light-Near old Asian woman had symptoms of palsy, tonic near response, delayed Dissociation in Lesions headache and diplopia. Oculomo- redilation on looking back into the of the Rostral Midbrain tor examination findings demon- distance) or anterior segment patho- strated a vertical gaze palsy with con- logic conditions, nor were there any vergence-retraction nystagmus, clinical signs of a third cranial nerve Examination of the pupillary re- noncomitant skew deviation, and palsy. Her visual acuity and color vi- sponse to light and accommoda- convergence insufficiency but pres- sion were normal. Magnetic reso- tion can provide precise informa- ervation of all other eye move- nance imaging of the brain showed tion concerning the localization of ments. Examination of the pupils re- a hyperintense lesion at the level of a lesion within the sympathetic and vealed moderate anisocoria, with the the rostral midbrain immediately to parasympathetic pathways, the an- right pupil being 0.50 mm larger the right of the aqueduct of Syl- terior visual pathway, or the brain- than the left in both bright light and vius, within the periaqueductal gray stem (Table 1). Classical teaching has associated all lesions of the ros- in the dark (Table 2). The light re- (Figure 2A and B). tral midbrain with bilateral light- sponse (LR) and the near response Case 2. A 31-year-old man had a near dissociation (LND), defined as in the left eye were equally brisk and sudden-onset headache, vomiting, attenuation of the pupil light reflex normal; however, in the right eye and poor balance. He reported ver- (PLR) with relative sparing of the there was attenuation of the light re- tical diplopia and difficulty focus- near response, as one component of flex but preservation of a normal ing on near targets. Oculomotor ex- Parinaud syndrome. We describe 2 brisk near response (LND). These amination findings revealed a patients with rostral midbrain le- findings were confirmed by formal noncomitant skew deviation with sions in whom LND was clinically measurement of the amplitudes of right hypertropia on right gaze but present only in the eye ipsilateral to the LR and near response in each full horizontal eye movements. Pa- the lesion. To our knowledge, this eye, recorded separately under mon- resis of vertical eye movements and clinical phenomenon has not been ocular conditions, using infrared an up-gaze saccadic palsy with con- previously reported. We provide an video pupillometry.1 In the left eye vergence-retraction nystagmus was explanation for this observation and both the LR and the near response present. Visual acuity and color vi- its implications for our understand- were normal with no LND sion were normal. Examination of ing of the anatomy of the pupil light (Figure 1A). Slitlamp examina- the pupils under resting conditions pathway. tion showed no evidence of a tonic showed a small degree of anisoco- Table 1. Expected Pupil Examination Findings in Various Lesions of the Afferent, Central, and Efferent Limbs of the Pupillary Light Reflex Pathway Pupil Measurement Resting Pupil Diametera Direct Light Consensual Near Description Lesion Eye Dark Light Responseb Light Responseb Responseb of Pupil Sign Right optic nerve R Normal Normal ↓ Normal Normal Ipsilateral RAPD L Normal Normal Normal ↓ Normal Right optic tract R Normal Normal Normal ↓ Normal Contralateral RAPD L Normal Normal ↓ Normal Normal Dorsal midbrain-midline (PC) R Normal ↑↓ ↓ Normal Bilateral LND L Normal ↑↓ ↓ Normal Right ventral midbrain R Normal ↑↓ ↓ Normal Ipsilateral LND L Normal Normal Normal Normal Normal Ipsilateral unreactive pupil Right preganglionic P/S fibers R Normal ↑↓ ↓ ↓ L Normal Normal Normal Normal Normal Right postganglionic P/S fibers R ↓↑ ↓ ↓ ↑Ipsilateral tonic pupil (chronic) L Normal Normal Normal Normal Normal Abbreviations: LND, light-near dissociation; PC, posterior commissure; P/S, parasympathetic fibers; RAPD, relative afferent pupil defect. a The ↑ indicates an increase in mydriasis; ↓, decrease (myosis) in the size of the pupil. b The ↑ indicates an increase in the speed of the pupil response to that stimulus; ↓, a decrease in the speed of the pupil response to that stimulus. (REPRINTED) ARCH OPHTHALMOL / VOL 128 (NO. 11), NOV 2010 WWW.ARCHOPHTHALMOL.COM 1486 ©2010 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/27/2021 ria in the dark (the right pupil being larger than the left) that increased Table 2. Pupillary Measurements From Both Right and Left Eyes of Patients 1 and 2 in bright light (Table 2). Clinically the right pupil showed an attenu- Resting Pupil Diameter, mm ated direct LR compared with that Direct Light Near measured in the left pupil, but the Patient No. Eye Dark Light Response, mm Response, mm near responses were brisk and of 1 normal amplitude in both eyes. As Initially R 7.20 6.00 1.23 2.60 a result, LND was found on the right L 6.70 5.50 2.04 1.48 side but not on the left side 1 y later R 7.40 5.35 2.50 2.36 (Figure 1B). There were no signs of L 7.65 5.52 3.00 2.60 2 R 6.25 4.20 1.60 2.00 a tonic pupil or third cranial nerve L 5.95 3.15 2.10 1.60 palsy. A magnetic resonance image of the brain revealed a small hem- orrhage secondary to a midbrain ar- teriovenous malformation on the A B right of the aqueduct of Sylvius (Figure 2C). He slowly recovered with a minor residual vertical eye movement deficit. Comment. The patients described demonstrate the novel finding of unilateral LND in association with some other components of a dorsal midbrain syndrome, namely, supra- nuclear up-gaze palsy, impaired con- vergence, and convergence- retraction nystagmus on attempted up gaze. This finding was clinically apparent. We were careful to ex- clude infranuclear causes of unilat- eral LND, including aberrant regen- Figure 1. Pupillograms recorded from patients 1 (A) and 2 (B) using an infrared pupillometer (series eration of the third cranial nerve (eg, 1800; Whittaker Corporation, Simi Valley, California). (See Fison et al1 for methods of eliciting and miosis associated with attempted ad- recording the light and near responses). The recordings were made under monocular conditions, with the pupil response being recorded in all cases from the eye that was stimulated (ie, consensual responses duction, elevation, or depression of were not recorded). Upper traces are of the right eye; lower traces, the left eye. The responses to light the eye), a chronic postganglionic (standardized 1 second square-wave pulse under Maxwellian optics) are shown on the left; the responses parasympathetic lesion (eg, irregu- to an accommodative effort are shown on the right. Scale bars indicate vertical measure of 0.5 mm; lar pupil shape, sector palsy, exag- horizontal, 2 seconds (A; also B right-hand trace) or 1 second (B, left hand trace). gerated but tonic response to an ac- eral pupil under bright lighting con- Alternatively, it may simply be that commodative effort), or local ditions because the light signal can- any effect of the lesion on anisoco- pathologic features within the an- not reach the ipsilateral EWN from ria is being swamped by the many terior segment of the eye (eg, uve- either eye; in the dark, however, other central influences that affect itis, iris ischemia, and others), but when EWN output is not affected by the tonic output of EWN cells (eg, neither of these cases showed signs the PON projections, there should projections from the locus ceruleus). of a peripheral lesion. Given the lat- eralized and rostral location of the be less (or no) anisocoria. Only pa- In contrast, a lateralized and ros- midbrain lesions identified by neu- tient 2 showed the expected in- trally placed midbrain lesion is not roimaging in these cases, it is likely crease in anisocoria in the light, with expected to cause asymmetry in the that the asymmetric pupil signs were patient 1 showing an insignificant pupillary miosis that accompanies an instead caused by supranuclear dis- degree of anisocoria under all light- accommodative effort, yet both pa- ruption to the projections of the pre- ing conditions. It is hard to inter- tients showed larger amplitude near tectal olivary nuclei (PON) to the pret this lack of asymmetry in rest- responses in the ipsilateral eye. Pe- Edinger-Westphal nucleus (EWN) ing pupil size in patient 1. One ripheral (postganglionic) lesions are, on only one side, with relative spar- possibility is that the identified le- of course, often characterized by ex- ing of the PON projections to the sion may also be disrupting the cen- aggerated near responses, but nei- other EWN. tral inhibitory projections to the ther of the near responses in these Such lateralized dorsal mid- EWN, resulting in relative disinhi- patients were tonic or exaggerated; brain lesions might also be ex- bition and miosis of the pupil that therefore, a supranuclear mecha- pected to cause anisocoria. The rest- would counteract any mydriatic ef- nism must be invoked by way of ex- ing diameter of the ipsilateral pupil fects of removing the excitatory light planation. It is unfortunate that the should be larger than the contralat- signal projections from both PON. near responses in both patients were (REPRINTED) ARCH OPHTHALMOL / VOL 128 (NO. 11), NOV 2010 WWW.ARCHOPHTHALMOL.COM 1487 ©2010 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/27/2021 A B C Figure 2. A, Patient 1. Sagittal T2-weighted brain magnetic resonance image showing a hyperintense lesion at the level of the rostral midbrain. B, Axial sectionin patient 1 shows that the lesion is located to the right of the aqueduct of Sylvius within the periaqueductal gray.
Load more

Recommended publications
  • Neuroanatomy Crash Course
    Neuroanatomy Crash Course Jens Vikse ∙ Bendik Myhre ∙ Danielle Mellis Nilsson ∙ Karoline Hanevik Illustrated by: Peder Olai Skjeflo Holman ​ Second edition October 2015 The autonomic nervous system ● Division of the autonomic nervous system …………....……………………………..………….…………... 2 ● Effects of parasympathetic and sympathetic stimulation…………………………...……...……………….. 2 ● Parasympathetic ganglia ……………………………………………………………...…………....………….. 4 Cranial nerves ● Cranial nerve reflexes ………………………………………………………………….…………..…………... 7 ● Olfactory nerve (CN I) ………………………………………………………………….…………..…………... 7 ● Optic nerve (CN II) ……………………………………………………………………..…………...………….. 7 ● Pupillary light reflex …………………………………………………………………….…………...………….. 7 ● Visual field defects ……………………………………………...................................…………..………….. 8 ● Eye dynamics …………………………………………………………………………...…………...………….. 8 ● Oculomotor nerve (CN III) ……………………………………………………………...…………..………….. 9 ● Trochlear nerve (CN IV) ………………………………………………………………..…………..………….. 9 ● Trigeminal nerve (CN V) ……………………………………………………................…………..………….. 9 ● Abducens nerve (CN VI) ………………………………………………………………..…………..………….. 9 ● Facial nerve (CN VII) …………………………………………………………………...…………..………….. 10 ● Vestibulocochlear nerve (CN VIII) …………………………………………………….…………...…………. 10 ● Glossopharyngeal nerve (CN IX) …………………………………………….……….…………...………….. 10 ● Vagus nerve (CN X) …………………………………………………………..………..…………...………….. 10 ● Accessory nerve (CN XI) ……………………………………………………...………..…………..………….. 11 ● Hypoglossal nerve (CN XII) …………………………………………………..………..…………...………….
    [Show full text]
  • Real Time Measurement and Processing of Pupillary Light Reflex for Early Detection of Disease
    Journal of Computers Real Time Measurement and Processing of Pupillary Light Reflex for Early Detection of Disease Ippei Torii*, Takahito Niwa Aichi Institute of Technology, Dept. of Information Science, 1247 Yachigusa, Yakusa-cho, Toyota, Aichi, Japan. * Corresponding author. Tel.: 81-565-48-8121; email: mac[aitech.ac.jp Manuscript submitted January 10, 2019; accepted March 8, 2019. doi: 10.17706/jcp.14.3.161-169 Abstract: Recently, pupillary measurements have begun to be considered effective in the diagnosis of various physical conditions. Apart from optic neuropathy and retinal disorders, which are ocular diseases, diversions can be expected in the diagnosis of autonomic disturbance due to sympathetic and parasympathetic nerve disorders, cranial nerve disorders, cerebral infarction, depression, and diabetes. In this study, we have developed a real-time pupil diameter measuring system that is inexpensive and does not require a complicated device. When strong light is projected onto the eyeball, this system can measure the reaction time until the start of miosis, the time to achieve maximal miosis, and the difference in reaction speed of the left and right eyes. With this system, the status of a disease can be judged based on the distance from the threshold value. Key words: Real time measurement, eye movement, early detection of disease, image processing. 1. Introduction There are approximately one hundred million photoreceptor cells in the retina of human eyes. Light that shines on those cells is converted to nerve signals, which transmit the information to the brain, resulting in the visual recognition of objects. When light is radiated onto the eye, the pupillary light reflex is triggered, causing the pupillary diameter to decrease with a time delay of less than 1 sec.
    [Show full text]
  • Structural Brain Abnormalities in Patients with Primary Open-Angle Glaucoma: a Study with 3T MR Imaging
    Glaucoma Structural Brain Abnormalities in Patients with Primary Open-Angle Glaucoma: A Study with 3T MR Imaging Wei W. Chen,1–3 Ningli Wang,1,3 Suping Cai,3,4 Zhijia Fang,5 Man Yu,2 Qizhu Wu,5 Li Tang,2 Bo Guo,2 Yuliang Feng,2 Jost B. Jonas,6 Xiaoming Chen,2 Xuyang Liu,3,4 and Qiyong Gong5 PURPOSE. We examined changes of the central nervous system CONCLUSIONS. In patients with POAG, three-dimensional MRI in patients with advanced primary open-angle glaucoma revealed widespread abnormalities in the central nervous (POAG). system beyond the visual cortex. (Invest Ophthalmol Vis Sci. 2013;54:545–554) DOI:10.1167/iovs.12-9893 METHODS. The clinical observational study included 15 patients with bilateral advanced POAG and 15 healthy normal control subjects, matched for age and sex with the study group. Retinal rimary open angle glaucoma (POAG) has been defined nerve fiber layer (RNFL) thickness was measured by optical formerly by intraocular morphologic changes, such as coherence tomography (OCT). Using a 3-dimensional magne- P progressive retinal ganglion cell loss and defects in the retinal tization-prepared rapid gradient-echo sequence (3D–MP-RAGE) nerve fiber layer (RNFL), and by corresponding psychophysical of magnetic resonance imaging (MRI) and optimized voxel- abnormalities, such as visual field loss.1 Recent studies by based morphometry (VBM), we measured the cross-sectional various researchers, however, have suggested that the entire area of the optic nerve and optic chiasm, and the gray matter visual pathway may be involved in glaucoma.2–23 Findings from volume of the brain.
    [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]
  • 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]
  • Congenital Oculomotor Palsy: Associated Neurological and Ophthalmological Findings
    CONGENITAL OCULOMOTOR PALSY: ASSOCIATED NEUROLOGICAL AND OPHTHALMOLOGICAL FINDINGS M. D. TSALOUMAS1 and H. E. WILLSHA W2 Birmingham SUMMARY In our group of patients we found a high incidence Congenital fourth and sixth nerve palsies are rarely of neurological abnormalities, in some cases asso­ associated with other evidence of neurological ahnor­ ciated with abnormal findings on CT scanning. mality, but there have been conflicting reports in the Aberrant regeneration, preferential fixation with literature on the associations of congenital third nerve the paretic eye, amblyopia of the non-involved eye palsy. In order to clarify the situation we report a series and asymmetric nystagmus have all been reported as 1 3 7 of 14 consecutive cases presenting to a paediatric associated ophthalmic findings. - , -9 However, we tertiary referral service over the last 12 years. In this describe for the first time a phenomenon of digital lid series of children, 5 had associated neurological elevation to allow fixation with the affected eye. Two abnormalities, lending support to the view that con­ children demonstrated this phenomenon and in each genital third nerve palsy is commonly a manifestation of case the accompanying neurological defect was widespread neurological damage. We also describe for profound. the first time a phenomenon of digital lid elevation to allow fixation with the affected eye. Two children demonstrated this phenomenon and in each case the PATIENTS AND METHODS accompanying neurological defect was profound. The Fourteen children (8 boys, 6 girls) with a diagnosis of frequency and severity of associated deficits is analysed, congenital oculomotor palsy presented to our paed­ and the mechanism of fixation with the affected eye is iatric tertiary referral centre over the 12 years from discussed.
    [Show full text]
  • Embryology, Anatomy, and Physiology of the Afferent Visual Pathway
    CHAPTER 1 Embryology, Anatomy, and Physiology of the Afferent Visual Pathway Joseph F. Rizzo III RETINA Physiology Embryology of the Eye and Retina Blood Supply Basic Anatomy and Physiology POSTGENICULATE VISUAL SENSORY PATHWAYS Overview of Retinal Outflow: Parallel Pathways Embryology OPTIC NERVE Anatomy of the Optic Radiations Embryology Blood Supply General Anatomy CORTICAL VISUAL AREAS Optic Nerve Blood Supply Cortical Area V1 Optic Nerve Sheaths Cortical Area V2 Optic Nerve Axons Cortical Areas V3 and V3A OPTIC CHIASM Dorsal and Ventral Visual Streams Embryology Cortical Area V5 Gross Anatomy of the Chiasm and Perichiasmal Region Cortical Area V4 Organization of Nerve Fibers within the Optic Chiasm Area TE Blood Supply Cortical Area V6 OPTIC TRACT OTHER CEREBRAL AREASCONTRIBUTING TO VISUAL LATERAL GENICULATE NUCLEUSPERCEPTION Anatomic and Functional Organization The brain devotes more cells and connections to vision lular, magnocellular, and koniocellular pathways—each of than any other sense or motor function. This chapter presents which contributes to visual processing at the primary visual an overview of the development, anatomy, and physiology cortex. Beyond the primary visual cortex, two streams of of this extremely complex but fascinating system. Of neces- information flow develop: the dorsal stream, primarily for sity, the subject matter is greatly abridged, although special detection of where objects are and for motion perception, attention is given to principles that relate to clinical neuro- and the ventral stream, primarily for detection of what ophthalmology. objects are (including their color, depth, and form). At Light initiates a cascade of cellular responses in the retina every level of the visual system, however, information that begins as a slow, graded response of the photoreceptors among these ‘‘parallel’’ pathways is shared by intercellular, and transforms into a volley of coordinated action potentials thalamic-cortical, and intercortical connections.
    [Show full text]
  • Eye Essentials 5
    continuing education 33 Eye essentials 5 Successful participation in each Classification and localisation module of this approved series counts as one credit towards the GOC CET scheme administered by Vantage and of visual field defects one towards the AOI’s scheme. In the last of our features based on the Eye Essential textbooks, Dr Robert Cubbidge describes the visual pathway and its relationship with the visual field. CET module C2354 This article has been adapted and abridged from Visual Fields by Dr THE DIMENSION of the blind spot Robert Cubbidge, is approximately 7.5º high and 5.5º wide part of the new and represents the temporal visual field Eye Essentials projection of the optic nerve, found series. For further approximately 1.5º below and 15º horizon- information, tally from fixation. When interpreting including ordering, please click on visual field defects, knowledge of the the Bookstore link arrangement of nerve fibres in the visual at www.optician pathway is essential. online.net Depending on the site of damage in the visual pathway, characteristic visual field defects are produced (Figure 1). course to the optic nerve as they are not Anatomically, the visual pathway hindered by the papillomacular bundle begins at the photoreceptors which lie in (Figure 2). The nerve fibres from the nasal the outer retina. Here, photons of light are retina do not cross those of the temporal absorbed by the photopigments, which are retina and thereby form a theoretical sensitive to specific regions of the visible vertical line of demarcation which passes electromagnetic spectrum. Light energy through the centre of the fovea.
    [Show full text]
  • The Pupillary Light Reflex in Normal Subjects
    Br J Ophthalmol: first published as 10.1136/bjo.65.11.754 on 1 November 1981. Downloaded from British Journal ofOphthalmology, 1981, 65, 754-759 The pupillary light reflex in normal subjects C. J. K. ELLIS From St Thomas's Hospital, London SE] SUMMARY In 19 normal subjects the pupillary reflex to light was studied over a range of stimulus intensities by infrared electronic pupillography and analysed by a computer technique. Increasing stimulus intensity was associated with an increase in direct light reflex amplitude and maximum rate of constriction and redilatation. Latency from stimulus to onset of response decreased with increas- ing stimulus intensity. The normal range for each of these parameters is given and the significance of these results in clinical pupillary assessment discussed. The technique of infrared pupillometry' has allowed PUPILLOMETRY the normal pupillary response to light to be studied in A Whittaker Series 1800 binocular infrared television detail. Lowenstein and Friedman2 have shown that pupillometer was used in this study. All recordings in response to light the pupil constricts after a latent were made in darkness with no correction for refrac- period and that the length of this latent period, the tive error. The eyes were illuminated from a low- copyright. amplitude of the response, and the speed of the intensity, invisible infrared source and observed by pupillary constriction are dependent on the stimulus means of a closed circuit television system sensitive to intensity employed. These findings have subse- infrared light. The pupils were displayed on television quently been confirmed.3" monitor screens providing instantaneous feedback of Borgmann6 gave 95% confidence limits in defining the quality of the pupil images.
    [Show full text]
  • Anatomy and Physiology of the Afferent Visual System
    Handbook of Clinical Neurology, Vol. 102 (3rd series) Neuro-ophthalmology C. Kennard and R.J. Leigh, Editors # 2011 Elsevier B.V. All rights reserved Chapter 1 Anatomy and physiology of the afferent visual system SASHANK PRASAD 1* AND STEVEN L. GALETTA 2 1Division of Neuro-ophthalmology, Department of Neurology, Brigham and Womens Hospital, Harvard Medical School, Boston, MA, USA 2Neuro-ophthalmology Division, Department of Neurology, Hospital of the University of Pennsylvania, Philadelphia, PA, USA INTRODUCTION light without distortion (Maurice, 1970). The tear–air interface and cornea contribute more to the focusing Visual processing poses an enormous computational of light than the lens does; unlike the lens, however, the challenge for the brain, which has evolved highly focusing power of the cornea is fixed. The ciliary mus- organized and efficient neural systems to meet these cles dynamically adjust the shape of the lens in order demands. In primates, approximately 55% of the cortex to focus light optimally from varying distances upon is specialized for visual processing (compared to 3% for the retina (accommodation). The total amount of light auditory processing and 11% for somatosensory pro- reaching the retina is controlled by regulation of the cessing) (Felleman and Van Essen, 1991). Over the past pupil aperture. Ultimately, the visual image becomes several decades there has been an explosion in scientific projected upside-down and backwards on to the retina understanding of these complex pathways and net- (Fishman, 1973). works. Detailed knowledge of the anatomy of the visual The majority of the blood supply to structures of the system, in combination with skilled examination, allows eye arrives via the ophthalmic artery, which is the first precise localization of neuropathological processes.
    [Show full text]
  • Melanopsin and Cone Photoreceptor Inputs to the Afferent Pupil Light Response
    ORIGINAL RESEARCH published: 22 May 2019 doi: 10.3389/fneur.2019.00529 Melanopsin and Cone Photoreceptor Inputs to the Afferent Pupil Light Response Andrew J. Zele 1,2*, Prakash Adhikari 1,2, Dingcai Cao 3 and Beatrix Feigl 1,4,5 1 Institute of Health and Biomedical Innovation, Queensland University of Technology (QUT), Brisbane, QLD, Australia, 2 School of Optometry and Vision Science, Queensland University of Technology (QUT), Brisbane, QLD, Australia, 3 Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, United States, 4 School of Biomedical Sciences, Queensland University of Technology (QUT), Brisbane, QLD, Australia, 5 Queensland Eye Institute, Brisbane, QLD, Australia Background: Retinal photoreceptors provide the main stage in the mammalian eye for regulating the retinal illumination through changes in pupil diameter, with a small population of melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) forming the primary afferent pathway for this response. The purpose of this Edited by: study is to determine how melanopsin interacts with the three cone photoreceptor Victoria Susan Pelak, University of Colorado Denver, classes in the human eye to modulate the light-adapted pupil response. United States Methods: We investigated the independent and combined contributions of the inner Reviewed by: and outer retinal photoreceptor inputs to the afferent pupil pathway in participants with Jason Charng, Lions Eye Institute, Australia trichromatic color vision using a method to independently control the excitations of Chiara La Morgia, ipRGCs, cones and rods in the retina. IRCCS Istituto delle Scienze Neurologiche di Bologna (ISNB), Italy Results: We show that melanopsin-directed stimuli cause a transient pupil constriction *Correspondence: generated by cones in the shadow of retinal blood vessels; desensitizing these penumbral Andrew J.
    [Show full text]