DOCSLIB.ORG

Auditory Evoked Phosphenes in Optic Nerve Disease

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Auditory Evoked Phosphenes in Optic Nerve Disease J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.45.1.7 on 1 January 1982. Downloaded from Jouirnial of Neurology, Neurosurgerv, c(lid Psychiatry 1982;45:7-12 Auditory evoked phosphenes in optic nerve disease NGR PAGE, JP BOLGER, MD SANDERS From the Medical Ophthalmology Unit, St Thomas' Hospital, Lonidon SUMMARY Five patients with optic neuropathy, four vascular and one demyelinating, are described who each complained of an unusual symptom. Bright flashes of light (phosphenes) occurred in the affected eyes and were evoked by sudden unexpected sounds. Movement of the eye alone did not reproduce the symptom. In all patients the phenomenon was sufficiently prominent to interfere with sleep and was the main complaint of one patient. An anticonvulsant (phenytoin) greatly reduced the frequency and intensity of the phosphene in one patient. Phosphenes are visual sensations perceived in the flash; a car door slamming or a cough were the most absence of visual (luminous) stimuli and may occur consistently effective sounds. The onset of a continuous in optic nerve disease, but are unusual. Eye movement sound might elicit a single discrete flash and there was phosphenes in optic neuritis are now well recognised1 no "off" phenomenon at the end of the sound. Neither and phosphenes induced by sound have been de- the loudness, nor the direction of the sounds, nor the ear in which it was heard affected the subjective quality Protected by copyright. scribed in three patients with different ocular of the flash. Anticipated sounds would not evoke a conditions.2 Other positive visual phenomena may response and nor would blinking or voluntary or invol- also be seen in optic nerve disease. Chromatopsia untary eye movements, however rapid. may be a feature of Leber's optic neuropathy and Examination at this time did not reveal any abnormal- tabetic optic atrophy and may occur in drug- ities other than in the right eye. Visual acuity in the right induced toxic optic neuropathy.3 We have observed eye was 6/60, N24 and no Ishihara colour plates could be central visual loss in Leber's optic neuropathy due identified. He had a right relative afferent pupil defect. to scotomata described as "dense clouds of brilliant Ocular movements and slit lamp examination were coloured lights". We describe five patients with normal. The optic disc was swollen in the superonasal quadrant and the arteries were attenuated. Visual field anterior optic nerve disease with sound or auditory charting showed an inferonasal sector defect to all evoked phosphenes and discuss the possible mech- isoptres on the Goldmann Chart (fig 1). A diagnosis of anism for this. All the patients presented with ischaemic optic neuropathy was made. Fluorescein rapid unilateral visual loss, optic disc swelling and angiography showed leakage of fluorescein at the disc large sectorial visual field defects. with a normal retinal circulation. Visual evoked responses (VER) showed abolished pattern response on the right Case 1 and the flash VER was extremely subnormal and delayed. A 55-year-old man, whilst rubbing his left eye, suddenly The electrooculogram (EOG) and the electroretinogram http://jnnp.bmj.com/ became aware that vision in the lower nasal field of the (ERG) were normal on the right side as was the VER right eye had become blurred. Vision in that eye de- from the left eye. Attempts to evoke a flash by sound or teriorated over the next week, with a resultant acuity of to detect any response in the VER or ERG were un- 6/60. There was no headache or pain on eye movement successful. For a period of weeks the symptom persisted but he began to experience disturbing single bright causing significant distress and interfered with any form flashes in the right eye initiated by unexpected sounds. The of relaxation. Eventually the frequency of phosphenes flashes wereblue-whiteand discrete, lasting only an instant, reducing to a level allowing normal sleep and ceased and did not contain any formed elements. He was unable after about eight months. His visual acuity has remained to localise the flash within the visual field. This symptom at counting fingers and optic atrophy has developed. on September 30, 2021 by guest. occurred during the day but was most troublesome when he was in a reduced state of wakefulness such as prior Case 2 to falling asleep. Only unexpected sounds evoked the A 38-year-old dustman who had been perfectly well, developed a foreign body sensation in his right eye. Address for reprint requests: NGR Page, St Thomas' After two days he awoke with a dark mist over the lower Hospital, London SEI 7EH. UK. part of the visual field of the right eye. This mist persisted, Received 8 August 1981 appearing to fluctuate in intensity over the next week, Accepted 29 August 1981 and has subsequently not changed. On several occasions 7 J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.45.1.7 on 1 January 1982. Downloaded from 8 Page, Bolger, Sanders Protected by copyright. Case 3 Case 5 not be charted Fig I Visualfields offour afJected eyes showing altitudinal and sectorial defects (the visual field could in one case due to poor acuity). http://jnnp.bmj.com/ by the sound of his own cough- he had a sharp pain in the right eye on eye movement The flash was often caused in both temporal regions. ing. Production of these flashes by voluntary eye or and in addition had an ache of at this time showed visual acuity of 6/6, head movements was not possible. The diagnosis Examination was of light was 60 % ischaemic optic neuropathy was made. CSF analysis N5 in the right eye. Appreciation vascular there was a right afferent pupil normal as were investigations for an underlying compared to the left and disc leakage. an inferior altitudinal loss, cause. Fluorescein angiography confirmed defect. Perimetry showed poorly with generalised depression superiorly in the right eye The visual evoked response had a low amplitude, was increased. Auditory (fig 1). On fundal examination the optic disc was swollen defined waveform and the latency linear peri-papilliary haemorrhage evoked responses and an EEG were normal, and it on September 30, 2021 by guest. with a superficial to unexpected 2). The vessels and retina were normal. Two weeks was again impossible to show any response (fig we were able to provoke after onset he began to develop flashes of light similar sounds with these tests, although at night prior to falling phosphenes by sounds whilst he was resting in darkness. to the other cases. These occurred did not asleep. A loud noise startling him caused a momentary A tactile stimulus causing a startle response in the centre of the right eye cause a phosphene. He was treated with phenytoin bright white phosphene in the and sound would cause a dull yellow phos- 300 mg daily with a reduction frequency whereas a quiet such that loud sounds phene. Again, he said this was often caused by his wife intensity of the phosphenes, sometimes provoke a dull yellow flash. talking or moving in bed, or animals or cars outside, would then only J Neurol Neurosurg Psychiatry: first published as 10.1136/jnnp.45.1.7 on 1 January 1982. Downloaded from AuditorY evoked phosphenes in optic nier-ve disease 9 Fig 2 Case 2. Fundus photograph (a) andfluiorescein angiograms (b, c) showing a swollen leaking optic disc with dilated capillaries and a superficial haeunorrhage. Case 3 but with no change in vision, and he has remained on a A 68-year-old man noticed a white-yellow flash of light small maintenance dose of steroids. A month later he in his left eye which was elicited by sounds. The patient, noticed white flashes in the affected eye. These phosphenes a retired optician, observed progress of this symptom were like "a photographic flash" and appeared in the with interest. He reported that it occurred only on central part of the left eye. He was a light sleeper and the Protected by copyright. hearing sudden or unexpected sounds particularly when phosphenes occur "in the quiet of night" when he was he was feeling sleepy. Voluntary eye movements could awake. Any unexpected noise, whether loud or quiet, not produce it. The symptoms were remarkably like those and not always startling, would immediately evoke a of Case I in that the discrete flash was always of the same phosphene, and this now occurred several times each character and produced by sounds such as car doors night. Again, these phosphenes could not be produced by closing, coughing, footsteps or his wife turning over in voluntary or involuntary eye movements or blinking. bed. Although the symptoms became more disturbing The auditory evoked phosphenes have continued he did not seek advice until he awoke one morning unchanged for four years and do not now distress him. with blurred vision in the left eye. Examination of the eye showed acuity of 6/9, NIO. There was an afferent Case 5 pupil defect and a pale waxy swollen disc with a few A 30-year-old seaman noticed some blurring of vision intra retinal haemorrhages nearby. The Goldmann field in the left eye which deteriorated over the next two days demonstrated upper arcuate loss (fig 1) and examination and then persisted. Simultaneously, he developed pain of the right eye was normal. A diagnosis of left ischaemic in the left eye and orbit extending to the temple, which optic neuropathy was made. He was otherwise fit was constantly present but exacerbated by eye movements. with no other abnormalities on examination or haema- These complaints persisted and after two weeks he tological or biochemical testing.
Load more

Recommended publications
  • Advice for Floaters and Flashing Lights for Primary Care
    UK Vision Strategy RCGP – Royal College of General Practitioners Advice for Floaters and Flashing Lights for primary care Key learning points • Floaters and flashing lights usually signify age-related liquefaction of the vitreous gel and its separation from the retina. • Although most people sometimes see floaters in their vision, abrupt onset of floaters and / or flashing lights usually indicates acute vitreous gel detachment from the posterior retina (PVD). • Posterior vitreous detachment is associated with retinal tear in a minority of cases. Untreated retinal tear may lead to retinal detachment (RD) which may result in permanent vision loss. • All sudden onset floaters and / or flashing lights should be referred for retinal examination. • The differential diagnosis of floaters and flashing lights includes vitreous haemorrhage, inflammatory eye disease and very rarely, malignancy. Vitreous anatomy, ageing and retinal tears • The vitreous is a water-based gel containing collagen that fills the space behind the crystalline lens. • Degeneration of the collagen gel scaffold occurs throughout life and attachment to the retina loosens. The collagen fibrils coalesce, the vitreous becomes increasingly liquefied and gel opacities and fluid vitreous pockets throw shadows on to the retina resulting in perception of floaters. • As the gel collapses and shrinks, it exerts traction on peripheral retina. This may cause flashing lights to be seen (‘photopsia’ is the sensation of light in the absence of an external light stimulus). • Eventually, the vitreous separates from the posterior retina. Supported by Why is this important? • Acute PVD may cause retinal tear in some patients because of traction on the retina especially at the equator of the eye where the retina is thinner.
    [Show full text]
  • Eye-Movement Studies of Visual Face Perception
    Eye-movement studies of visual face perception Joseph Arizpe A dissertation submitted for the degree of Doctor of Philosophy of the University College London Institute of Cognitive Neuroscience University College London 2015 1 Declaration I, Joseph Arizpe, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. 2 Abstract This thesis investigates factors influencing eye-movement patterns during face perception, the relationship of eye-movement patterns to facial recognition performance, and methodological considerations impacting the detection of differences in eye-movement patterns. In particular, in the first study (chapter 2), in which the basis of the other-race effect was investigated, differences in eye- movement patterns during recognition of own- versus other-race (African, Chinese) faces were found for Caucasian participants. However, these eye- movement differences were subtle and analysis-dependent, indicating that the discrepancy in prior reports regarding the presence or absence of such differences are due to variability in statistical sensitivity of analysis methods across studies. The second and third studies (chapters 3 and 4) characterized visuomotor factors, specifically pre-stimulus start position and distance, which strongly influence subsequent eye-movement patterns during face perception. An overall bias in fixation patterns to the opposite side of the face induced by start position and an increasing undershoot of the first ordinal fixation with increasing start distance were found. These visuomotor influences were not specific to faces and did not depend on the predictability of the location of the upcoming stimulus.
    [Show full text]
  • Subliminal Afterimages Via Ocular Delayed Luminescence: Transsaccade Stability of the Visual Perception and Color Illusion
    ACTIVITAS NERVOSA SUPERIOR Activitas Nervosa Superior 2012, 54, No. 1-2 REVIEW ARTICLE SUBLIMINAL AFTERIMAGES VIA OCULAR DELAYED LUMINESCENCE: TRANSSACCADE STABILITY OF THE VISUAL PERCEPTION AND COLOR ILLUSION István Bókkon1,2 & Ram L.P. Vimal2 1Doctoral School of Pharmaceutical and Pharmacological Sciences, Semmelweis University, Budapest, Hungary 2Vision Research Institute, Lowell, MA, USA Abstract Here, we suggest the existence and possible roles of evanescent nonconscious afterimages in visual saccades and color illusions during normal vision. These suggested functions of subliminal afterimages are based on our previous papers (i) (Bókkon, Vimal et al. 2011, J. Photochem. Photobiol. B) related to visible light induced ocular delayed bioluminescence as a possible origin of negative afterimage and (ii) Wang, Bókkon et al. (Brain Res. 2011)’s experiments that proved the existence of spontaneous and visible light induced delayed ultraweak photon emission from in vitro freshly isolated rat’s whole eye, lens, vitreous humor and retina. We also argue about the existence of rich detailed, subliminal visual short-term memory across saccades in early retinotopic areas. We conclude that if we want to understand the complex visual processes, mere electrical processes are hardly enough for explanations; for that we have to consider the natural photobiophysical processes as elaborated in this article. Key words: Saccades Nonconscious afterimages Ocular delayed bioluminescence Color illusion 1. INTRODUCTION Previously, we presented a common photobiophysical basis for various visual related phenomena such as discrete retinal noise, retinal phosphenes, as well as negative afterimages. These new concepts have been supported by experiments (Wang, Bókkon et al., 2011). They performed the first experimental proof of spontaneous ultraweak biophoton emission and visible light induced delayed ultraweak photon emission from in vitro freshly isolated rat’s whole eye, lens, vitreous humor, and retina.
    [Show full text]
  • Visual Perception in Migraine: a Narrative Review
    vision Review Visual Perception in Migraine: A Narrative Review Nouchine Hadjikhani 1,2,* and Maurice Vincent 3 1 Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02129, USA 2 Gillberg Neuropsychiatry Centre, Sahlgrenska Academy, University of Gothenburg, 41119 Gothenburg, Sweden 3 Eli Lilly and Company, Indianapolis, IN 46285, USA; [email protected] * Correspondence: [email protected]; Tel.: +1-617-724-5625 Abstract: Migraine, the most frequent neurological ailment, affects visual processing during and between attacks. Most visual disturbances associated with migraine can be explained by increased neural hyperexcitability, as suggested by clinical, physiological and neuroimaging evidence. Here, we review how simple (e.g., patterns, color) visual functions can be affected in patients with migraine, describe the different complex manifestations of the so-called Alice in Wonderland Syndrome, and discuss how visual stimuli can trigger migraine attacks. We also reinforce the importance of a thorough, proactive examination of visual function in people with migraine. Keywords: migraine aura; vision; Alice in Wonderland Syndrome 1. Introduction Vision consumes a substantial portion of brain processing in humans. Migraine, the most frequent neurological ailment, affects vision more than any other cerebral function, both during and between attacks. Visual experiences in patients with migraine vary vastly in nature, extent and intensity, suggesting that migraine affects the central nervous system (CNS) anatomically and functionally in many different ways, thereby disrupting Citation: Hadjikhani, N.; Vincent, M. several components of visual processing. Migraine visual symptoms are simple (positive or Visual Perception in Migraine: A Narrative Review. Vision 2021, 5, 20. negative), or complex, which involve larger and more elaborate vision disturbances, such https://doi.org/10.3390/vision5020020 as the perception of fortification spectra and other illusions [1].
    [Show full text]
  • Phosphene Perception Is Due to the Ultra-Weak Photon Emission Produced in Various Parts of the Visual System: Glutamate in the Focus
    Zurich Open Repository and Archive University of Zurich Main Library Strickhofstrasse 39 CH-8057 Zurich www.zora.uzh.ch Year: 2016 Phosphene perception is due to the ultra-weak photon emission produced in various parts of the visual system: glutamate in the focus Császár, Noémi ; Scholkmann, Felix ; Salari, Vahid ; Szőke, Henrik ; Bókkon, István Abstract: Phosphenes are experienced sensations of light, when there is no light causing them. The physiological processes underlying this phenomenon are still not well understood. Previously, we proposed a novel biopsychophysical approach concerning the cause of phosphenes based on the assumption that cellular endogenous ultra-weak photon emission (UPE) is the biophysical cause leading to the sensation of phosphenes. Briefly summarized, the visual sensation of light (phosphenes) is likely to be duetothe inherent perception of UPE of cells in the visual system. If the intensity of spontaneous or induced photon emission of cells in the visual system exceeds a distinct threshold, it is hypothesized that it can become a conscious light sensation. Discussing several new and previous experiments, we point out that the UPE theory of phosphenes should be really considered as a scientifically appropriate and provable mechanism to explain the physiological basis of phosphenes. In the present paper, we also present our idea that some experiments may support that the cortical phosphene lights are due to the glutamate-related excess UPE in the occipital cortex. DOI: https://doi.org/10.1515/revneuro-2015-0039 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-126012 Journal Article Published Version Originally published at: Császár, Noémi; Scholkmann, Felix; Salari, Vahid; Szőke, Henrik; Bókkon, István (2016).
    [Show full text]
  • Biorxives Gaze-Stabilization Pdf Creator
    bioRxiv preprint doi: https://doi.org/10.1101/2021.07.30.454479; this version posted August 1, 2021. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. Visuo-vestibular gaze control – conserved subcortical processing Tobias Wibble1,2, Tony Pansell2, Sten Grillner1, Juan Pérez-Fernández1,3,* 1The Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden 2The Department of Clinical Neuroscience, Marianne Bernadotte Centrum, St: Erik’s Eye Hospital, Karolinska Institutet, Stockholm, Sweden 3CINBIO, Universidade de Vigo, Campus universitario Lagoas, Marcosende, 36310 Vigo, Spain *Corresponding author: [email protected] Abstract Gaze stabilization compensates for movements of the head or external environment to minimize image blurring, which is critical for visually-guided behaviors. Multisensory information is used to stabilize the visual scene on the retina via the vestibulo-ocular (VOR) and optokinetic (OKR) reflexes. While the organization of neuronal circuits underlying VOR is well described across vertebrates, less is known about the contribution and evolutionary origin of the OKR circuits. Moreover, the integration of these two sensory modalities is still poorly understood. Here, we developed a novel experimental model, the isolated lamprey eye-brain-labyrinth preparation, to analyze the neuronal pathways underlying visuo-vestibular integration which allowed electrophysiological recordings while applying vestibular stimulation using a moving platform, coordinated with visual stimulation via two screens. We show that lampreys exhibit robust visuo-vestibular integration, with optokinetic information processed in the pretectum 1 bioRxiv preprint doi: https://doi.org/10.1101/2021.07.30.454479; this version posted August 1, 2021.
    [Show full text]
  • Eye Fields in the Frontal Lobes of Primates
    Brain Research Reviews 32Ž. 2000 413±448 www.elsevier.comrlocaterbres Full-length review Eye fields in the frontal lobes of primates Edward J. Tehovnik ), Marc A. Sommer, I-Han Chou, Warren M. Slocum, Peter H. Schiller Department of Brain and CognitiÕe Sciences, Massachusetts Institute of Technology, E25-634, Cambridge, MA 02139, USA Accepted 19 October 1999 Abstract Two eye fields have been identified in the frontal lobes of primates: one is situated dorsomedially within the frontal cortex and will be referred to as the eye field within the dorsomedial frontal cortexŽ. DMFC ; the other resides dorsolaterally within the frontal cortex and is commonly referred to as the frontal eye fieldŽ. FEF . This review documents the similarities and differences between these eye fields. Although the DMFC and FEF are both active during the execution of saccadic and smooth pursuit eye movements, the FEF is more dedicated to these functions. Lesions of DMFC minimally affect the production of most types of saccadic eye movements and have no effect on the execution of smooth pursuit eye movements. In contrast, lesions of the FEF produce deficits in generating saccades to briefly presented targets, in the production of saccades to two or more sequentially presented targets, in the selection of simultaneously presented targets, and in the execution of smooth pursuit eye movements. For the most part, these deficits are prevalent in both monkeys and humans. Single-unit recording experiments have shown that the DMFC contains neurons that mediate both limb and eye movements, whereas the FEF seems to be involved in the execution of eye movements only.
    [Show full text]
  • Visual Pathways
    Visual Pathways Michael Davidson Professor, Ophthalmology Diplomate, American College of Veterinary Ophthalmologists Department of Clinical Sciences College of Veterinary Medicine North Carolina State University Raleigh, North Carolina, USA <[email protected]> Vision in Animals Miller PE, Murphy CJ. Vision in Dogs. JAVMA. 1995; 207: 1623. Miller PE, Murphy CJ. Equine Vision. In Equine Ophthalmology ed. Gilger BC. 2nd ed. 2011: pp 398- 433. Ofri R. Optics and Physiology of Vision. In Veterinary Ophthalmology. ed. Gelatt KN 5th ed. 2013: 208-270, Visual Pathways, Responses and Reflexes: Relevant Structures Optic n (CN II) – somatic afferent Oculomotor n (CN III), Trochlear n (CN IV), Abducens n (CN VI) – somatic efferent to extraocular muscles Facial n (CN VII)– visceral efferent to eyelids Rostral colliculi – brainstem center that mediates somatic reflexes in response to visual stimuli Cerebellum Cerebro-cortex esp. occipital lobe www.studyblue.com Visual Pathway Visual Cortex Optic Radiation Lateral Geniculate Body www.studyblue.com Visual Field each cerebral hemisphere receives information from contralateral visual field (“the area that can be seen when the eye is directed forward”) visual field Visual Fiber (Retinotopic) Segregation nasal retinal fibers decussate at chiasm, temporal retinal fibers remain ipsilateral Nasal Temporal Retina Retina Fibers Fibers Decussate Remain Ipsilateral OD Visual Field OS Total visual field OD temporal nasal hemifield hemifield temporal nasal fibers fibers Nasal Temporal Retina = Retina = Temporal
    [Show full text]
  • Lmmunohistochemical Localization of Neuronal Nicotinic Receptors in the Rodent Central Nervous System
    The Journal of Neuroscience, October 1987, 7(10): 3334-3342 lmmunohistochemical Localization of Neuronal Nicotinic Receptors in the Rodent Central Nervous System L. W. Swanson,1v2 D. M. Simmons, I12 P. J. Whiting,’ and J. Lindstrom’ ‘The Salk Institute for Biological Studies, and 2Howard Hughes Medical Institute, La Jolla, California 92037 The distribution of nicotinic acetylcholine receptors (AChR) are structurally unrelated (Kubo et al., 1986a, b) to nicotinic in the rat and mouse central nervous system has been ACh receptors (AChR, Noda et al., 1983a, b), which act by mapped in detail using monoclonal antibodies to receptors regulating directly the opening of a cation channel that is an purified from chicken and rat brain. Initial studies in the intrinsic component of the molecule. Furthermore, subtypes of chicken brain indicate that different neuronal AChRs are con- neuronal AChRs have been identified on the basis of pharma- tained in axonal projections to the optic lobe in the midbrain cological and structural properties (Whiting et al., 1987a). To from neurons in the lateral spiriform nucleus and from retinal understand the functional significanceof ACh in a particular ganglion cells. Monoclonal antibodies to the chicken and rat neural system, it is therefore necessaryto establishthe cellular brain AChRs also label apparently identical regions in all localization of ACh, and the cellular localization and type of major subdivisions of the central nervous system of rats and cholinergic receptor with which it interacts. Immunohistochem- mice, and this pattern is very similar to previous reports of istry provides a sensitive method for localizing cholinergic neu- 3H-nicotine binding, but quite different from that of a-bun- rons with antibodies to the synthetic enzyme choline acetyl- garotoxin binding.
    [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]
  • Investigative Ophthalmology & Visual Science
    APRIL 1978 Vol. 17/4 Investigative Ophthalmology & Visual Science A Journal of Clinical and Basic Research Articles Training of voluntary torsion Richard Balliet and Ken Nakayama By means of a visual feedback technique, human subjects were trained to make large conjugate cyclorotary eye movements at will. The range of movement increased with training at a rate of approximately 0.8° per hour of practice, reaching 30° at the end of training. Photographs recorded the ability to make voluntary cyclofixations at any amplitude within the subject's range. Cyclotorsional pursuit was also trained, with ability increasing with greater amounts of visual feedback. In addition, torsional saccadic tracking was trained, showing a magnitude vs. peak velocity relationship similar to that seen for normal saccades. Control experiments indi- cate that all of these movements were voluntary, with no significant visual induction. With extended practice, large torsional movements could be made without any visual stimulation. The emergence of voluntary torsion through training demonstrates that the oculomotor system has more plasticity than has generally been assumed, reopening the issue as to whether other movements could also be trained to alleviate the symptoms of strabismus. Key words: eye movements, torsion, saccades, slow pursuit, fixation, orthoptics, oculomotor plasticity c' yclorotations are defined as rotations the eye can undergo a cyclorotation as it about the visual axis of the eye. These rota- moves from one tertiary position of gaze to tions are considered to be reflexive, with no another, but the amount of this cyclorotation indication of voluntary control. For example, is fixed, being dictated by Listings law.11 In addition, involuntary cyclovergence has been 1 From the Smith-Kettlewell Institute of Visual Science, reported to occur during convergence, and Department of Visual Sciences, University of the reflexive cycloversions have been demon- Pacific, San Francisco, Calif.
    [Show full text]
  • The Effect of Eye Movements and Blinks on Afterimage Appearance and Duration
    Journal of Vision (2015) 15(3):20, 1–15 http://www.journalofvision.org/content/15/3/20 1 The effect of eye movements and blinks on afterimage appearance and duration School of Psychology, Cardiff University, # Georgina Powell Cardiff, Wales, UK $ School of Psychology, Cardiff University, # Petroc Sumner Cardiff, Wales, UK $ Lyon Neuroscience Research Center, # Aline Bompas Centre Hospitalier Vinatier, Bron, Cedex, France $ The question of whether eye movements influence argued that afterimage signals are inherently ambigu- afterimage perception has been asked since the 18th ous, and this could explain why their visibility is century, and yet there is surprisingly little consensus on influenced by cues, such as surrounding luminance how robust these effects are and why they occur. The edges, more than are real stimuli (Powell, Bompas, & number of historical theories aiming to explain the Sumner, 2012). Helmholtz (1962) identified another cue effects are more numerous than clear experimental that is important to take into account when conducting demonstrations of such effects. We provide a clearer afterimage experiments: characterization of when eye movements and blinks do or do not affect afterimages with the aim to distinguish For obtaining really beautiful positive after- between historical theories and integrate them with a images, the following additional rules should be modern understanding of perception. We found neither saccades nor pursuit reduced strong afterimage observed. Both before and after they are devel- duration, and blinks actually increased afterimage oped, any movement of the eye or any sudden duration when tested in the light. However, for weak movement of the body must be carefully avoided, afterimages, we found saccades reduced duration, and because under such circumstances they invariably blinks and pursuit eye movements did not.
    [Show full text]