1 Eyes and Vision

Total Page:16

File Type:pdf, Size:1020Kb

1 Eyes and Vision Anatomy of the Eye Anatomy of the Eye Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I, All rights reserved Eyes and Vision Eyesight provides the brain with more input than all other senses combined. Each optic nerve contains one million nerve fibers. It is estimated that more than half of the information in the conscious mind enters through the eyes. The eyes are the most complex of the four special sense organs. All rights reserved All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 1 Anatomy of the Eye Sequence of Vision Rays of light enter the eye through the clear, domed front of the eyeball, the cornea, where they are partly bent (refracted). The rays then pass through the transparent lens, which changes shape to fine-focus the image, a mechanism known as accommodation. The light continues through the fluid, or vitreous humor, within the eyeball and shines an upside-down image onto the retina lining. The retina contains over 120 million cone cells and about 7 million rod signals. All rights reserved Sequence of Vision Rods are scattered through the retina and respond to low levels of light, but do not differentiate colors. Cones are concentrated in the fovea, need brighter conditions to function, and distinguish colors and fine details. Nerve fibers from the rods and cones connect via intermediate retinal cells to the fibers that form the optic nerve. Through this, the image is transmitted to the visual cortex in the brain, where it is turned upright. All rights reserved Path of Light Childhealth-explanation.com Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 2 Anatomy of the Eye Anatomy of the Eye The Human Eye is divided into three layers: Fibrous tunic (scleretic coat) This is the external layer of the eye. Two parts: Sclera (white of the eye) and Anterior Cornea Sclera includes: Episcleral layers Schlemm’s canal Trabecular meshwork Cornea contains: The limbus The following layers: Epithelial - Bowman’s – Stroma – Descemet’s – Endothelium All rights reserved Anatomy of the Eye Vascular tunic (uvea or choroid coat) This is the middle layer that is pigmented with melanin and provides the eye with it’s blood supply. Choroid Capillary lamina of choroids Bruch’s membrane Sattler’s layer Ciliary body Ciliary processes Ciliary muscle Iris Stroma Pupil Iris dilator muscle Iris sphincter muscle All rights reserved Anatomy of the Eye Retina: This is the inner layer of the eye composed primarily of nervous tissue. Its primary function is image formation. It contains: Cells Photoreceptor cells – rods, cones, horizontal Bipolar cells Retinal ganglion cells Layers Rods and cones Retinal pigment epithelium Macula Foveola Fovea All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 3 Anatomy of the Eye Other Parts of the Eye Anterior segment: Anterior chamber Aqueous humor Posterior chamber Lens Posterior segment Vitreous body (humor) Other Globe Eyelids Lacrimal system Orbit Optic nerve and visual pathways All rights reserved Anatomy and Function Conjunctiva: Clear, moist mucous membrane Assists in lubricating the eye Produces mucus and tears along with the lacrimal system Helps prevent foreign objects from penetrating into deeper structures of the eye. All rights reserved Anatomy and Function Sclera: White part of the eye. Opaque, protective, outer layer. Maintains the shape of the globe. Offers resistance to internal and external forces. Continuous with the dura mater and the cornea. All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 4 Anatomy of the Eye Anatomy and Function Cornea: Transparent fibrous coat the covers the front of the eye, including the iris, pupil and anterior chamber. Works with lens to refract light. After light enters the interior the light rays are bent so they can be brought to a fixed focus. Accounts for around two-thirds of the eye’s optical power. All rights reserved Choroid – Vascular Tunic Getty Images All rights reserved Choroid Is a highly vascular structure composed of capillaries and small arteries and veins that include connective tissue. It lies between the sclera and retina. It provides oxygen and other nutrients to the outer layers of the retina and together with the ciliary body and the iris, it forms the uveal tract. The choroid contains melanin which helps limit uncontrolled reflection within the eye that could result in the perception of mixed-up images. All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 5 Anatomy of the Eye Ciliary Body Controls accommodation (the process by which the eye changes optical power to maintain a clear image as the distance changes). Regulates flow of the aqueous humor into Schlemm’s canal. Coated by the epithelium, which produces the aqueous humor. All rights reserved Iris Is the colored part of the eye. Responsible for controlling the size and diameter of the pupil and the amount of light reaching the retina. Divides the area between the lens and the cornea into an anterior and posterior chamber. This is the primary location where intraocular pressure is regulated. Failure to control intraocular pressure can lead to disease, such a glaucoma. All rights reserved Retina The retina is a light-sensitive tissue lining that covers approximately 65% of the back inner surface of the eye. Rod and cone photosensitive cells, convert light energy into signals that are carried to the brain by the optic nerve. The fovea or fovea centralis (a small dimple) is the center of the eye’s sharpest vision and has the most color perception. All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 6 Anatomy of the Eye Rods and Cones All rights reserved Rods and Cones There are two distinct visual systems in the eye: Photopic vision is more sensitive to light, not color sensitive and is made up of rod cells. Scotopic vision is less sensitive to light, color sensitive and is made up of cone cells. The cylindrical shaped rod cells are located on the outer edges of the retina. Mainly used in peripheral vision, and because they require less light to function are also responsible for night vision. All rights reserved Rods and Cones There are three different types of cone cells, each of which absorb light from a different portions of the light spectrum. Cones that absorb long-wavelength light (reds) Cones that absorb middle-wavelength light (greens) Cones that absorb short-wavelength light (blues) Cone cells are a specialized type of nerve cell that are responsible for color perception and visual acuity. The macula located in the central area of the retina contains the cone cells. All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 7 Anatomy of the Eye Other Parts of the Eye Anterior Chamber: Is a space in the eye filled with aqueous humor, and lies between the iris and the cornea’s endothelium. Aqueous Humor: Flows through the pupil into the anterior chamber through a narrow cleft between the front of the lens and the back of the iris. Its main function is to provide optical power to the cornea. Also maintains intraocular pressure, shapes the globe. All rights reserved Other Parts of the Eye Posterior Chamber: Is the space behind the iris and in front of the lens. Holds aqueous humor for later transport to the anterior chamber. Lens: Is just in front of the iris. When the lens is relaxed, it’s flattened (increase in diameter – more light comes in) When the lens is contracted (decrease in diameter – less light comes in) This is called curvature of the lens and it enables the eye to adjust its focus between near and far objects. All rights reserved Other Parts of the Eye Lacrimal system: Contains structures for tear production and drainage. Lacrimal gland secretes tears and with its ecretory ducts, moves the fluid to the surface of the eye providing both normal amounts on the surface of the eye and extra amounts for tears. Vitreous body: Is the transparent, colorless, gel that fills the space between the lens and the retina. It holds the eye taut. This gel does not get replenished. Keeps the retina in place by pressing against the choroids and adhering to the retina. All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October 26, 2019 8 Anatomy of the Eye Optic Nerve The optic nerve is also known as the cranial nerve (CN) II. It transmits visual information from the retina to the brain. Is considered part of the CNS Three layers: Dura Arachnoid Pia mater All rights reserved Diseases and Disorders Retinal detachment: Retina is pulled or lifted away from its normal position. Cataracts: A partial or complete clouding on or in the lens which may obscure vision Myopia – nearsightedness Hypermetropia – farsightedness Glaucoma: A group of diseases characterized by damage to the optic nerve All rights reserved Diseases and Disorders Conjunctivitis: An infection of the conjunctiva Blepharitis: An inflammation of the eyelash follicles along the edge of the eyelid Corneal ulcers: An open sore on the cornea Dacryoadenitis: An inflammation of the tear-producing lacrimal gland. All rights reserved Coding Fiesta 2019 Sharon J. Oliver, CPC, CDEO, CRC, CPMA, CPC/CRC-I October
Recommended publications
  • AD Singh1, PA Rundle1, a Berry-Brincat1, MA Parsons2 and and Accommodation Were Considered Normal
    Tadpole pupil KL Koay et al 93 5 Currie ZI, Rennie IG, Talbot JF. Retinal vascular changes associated with transpupillary thermotherapy for choroidal melanomas. Retina 2000; 20: 620–626. 6 Shields CL, Cater J, Shields JA, Singh AD, Santos MCM, Carvalho C. Combination of clinical factors predictive of growth of small choroidal melanocytic tumors. Arch Ophthalmol 2000; 118: 360–364. 7 Journee-de Korver JG, Oosterhuis JA, de Wolff-Rouendaal D, Kemme H. Histopathological findings in human choroidal melanomas after transpupillary thermotherapy. Br J Ophthalmol 1997; 81: 234–239. 8 Anonymous. Histopathologic characteristics of uveal melanomas in eyes enucleated from the Collaborative Ocular Melanoma Study. COMS report no. 6. Am J Figure 1 Ophthalmol 1998; 125: 745–766. Tadpole-shaped pupil. 9 Diaz CE, Capone Jr A, Grossniklaus HE. Clinicopathologic findings in recurrent choroidal melanoma after transpupillary thermotherapy. Ophthalmology 1998; 105: 1419–1424. periocular sensation. The symptom occurred 10 Singh AD, Eagle Jr RC, Shields CL, Shields JA. Enucleation sporadically, sometimes with several weeks in between following transpupillary thermotherapy of choroidal episodes, but occasionally happening several times on melanoma :clinicopathologic correlations. Arch Ophthalmol the same day. There were no other visual symptoms and (in press). 11 Seregard S, Landau I. Transpupillary thermotherapy as an no significant past ocular history. General health was adjunct to ruthenium plaque radiotherapy for choroidal good and no regular medications were taken. melanoma. Acta Ophthalmologica Scand 2001; 79: 19–22. On examination, visual acuity was normal bilaterally. 12 Keunen JE, Journee-de Korver JG, Oosterhuis JA. There was a 1 mm right ptosis with mild anisocoria, the Transpupillary thermotherapy of choroidal melanoma with right pupil being 1 mm smaller in normal room or without brachytherapy: a dilemma.
    [Show full text]
  • Pupillary Disorders LAURA J
    13 Pupillary Disorders LAURA J. BALCER Pupillary disorders usually fall into one of three major cat- cortex generally do not affect pupillary size or reactivity. egories: (1) abnormally shaped pupils, (2) abnormal pupillary Efferent parasympathetic fibers, arising from the Edinger– reaction to light, or (3) unequally sized pupils (anisocoria). Westphal nucleus, exit the midbrain within the third nerve Occasionally pupillary abnormalities are isolated findings, (efferent arc). Within the subarachnoid portion of the third but in many cases they are manifestations of more serious nerve, pupillary fibers tend to run on the external surface, intracranial pathology. making them more vulnerable to compression or infiltration The pupillary examination is discussed in detail in and less susceptible to vascular insult. Within the anterior Chapter 2. Pupillary neuroanatomy and physiology are cavernous sinus, the third nerve divides into two portions. reviewed here, and then the various pupillary disorders, The pupillary fibers follow the inferior division into the orbit, grouped roughly into one of the three listed categories, are where they then synapse at the ciliary ganglion, which lies discussed. in the posterior part of the orbit between the optic nerve and lateral rectus muscle (Fig. 13.3). The ciliary ganglion issues postganglionic cholinergic short ciliary nerves, which Neuroanatomy and Physiology initially travel to the globe with the nerve to the inferior oblique muscle, then between the sclera and choroid, to The major functions of the pupil are to vary the quantity of innervate the ciliary body and iris sphincter muscle. Fibers light reaching the retina, to minimize the spherical aberra- to the ciliary body outnumber those to the iris sphincter tions of the peripheral cornea and lens, and to increase the muscle by 30 : 1.
    [Show full text]
  • The Nature of Foveal Representation Projections from the Nasal Part of the Retinae to Reach the Ipsilateral Hemispheres
    PERSPECTIVES OPINION hemiretina, project to the ‘wrong’ laminae of the LGN. These results were taken to show that the crossing of the nasal retinal fibres in the optic chiasm is incomplete, allowing some The nature of foveal representation projections from the nasal part of the retinae to reach the ipsilateral hemispheres. Normally, Michal Lavidor and Vincent Walsh however, foveal stimuli received by the nasal retinae are projected to the contralateral visual Abstract | A fundamental question in visual the visual midline. This is what Descartes1 cortex. A later study10 indicated that the perception is whether the representation of suggested in his description of the visual dendritic coverage of the centre of the fovea the fovea is split at the midline between the system — he identified the pineal gland as the by RGCs provides a possible neural basis for two hemispheres, or bilaterally represented organ of integration (FIG. 1).Unfortunately, 2–3° of bilateral representation of the fovea by overlapping projections of the fovea in this intuitive, appealing explanation is in the central visual pathways. There is also each hemisphere. Here we examine not true, and we therefore have to assume evidence that the nasotemporal overlap psychophysical, anatomical, that the two cerebral hemispheres cooperate increases towards the upper and lower regions neuropsychological and brain stimulation or compete over the representation of the of the retina11. experiments that have addressed this human foveal area. Most studies that have labelled RGCs with question, and argue for a shift from the When a person is fixating centrally (looking HRP after unilateral injections into the mon- current default view of bilateral straight ahead), information that is to key optic tract have found a nasotemporal representation to that of a split the right of fixation (in the right visual field) is overlap zone along the vertical meridian12.
    [Show full text]
  • Affections of Uvea Affections of Uvea
    AFFECTIONS OF UVEA AFFECTIONS OF UVEA Anatomy and physiology: • Uvea is the vascular coat of the eye lying beneath the sclera. • It consists of the uvea and uveal tract. • It consists of 3 parts: Iris, the anterior portion; Ciliary body, the middle part; Choroid, the third and the posterior most part. • All the parts of uvea are intimately associated. Iris • It is spongy having the connective tissue stroma, muscular fibers and abundance of vessels and nerves. • It is lined anteriorly by endothelium and posteriorly by a pigmented epithelium. • Its color is because of amount of melanin pigment. Mostly it is brown or golden yellow. • Iris has two muscles; the sphincter which encircles the pupil and has parasympathetic innervation; the dilator which extends from near the sphincter and has sympathetic innervation. • Iris regulates the amount of light admitted to the interior through pupil. • The iris separates the anterior chamber from the posterior chamber of the eye. Ciliary Body: • It extends backward from the base of the iris to the anterior part of the choroid. • It has ciliary muscle and the ciliary processes (70 to 80 in number) which are covered by ciliary epithelium. Choroid: • It is located between the sclera and the retina. • It extends from the ciliaris retinae to the opening of the optic nerve. • It is composed mainly of blood vessels and the pigmented tissue., The pupil • It is circular and regular opening formed by the iris and is larger in dogs in comparison to man. • It contracts or dilates depending upon the light source, due the sphincter and dilator muscles of the iris, respectively.
    [Show full text]
  • Foveola Nonpeeling Internal Limiting Membrane Surgery to Prevent Inner Retinal Damages in Early Stage 2 Idiopathic Macula Hole
    Graefes Arch Clin Exp Ophthalmol DOI 10.1007/s00417-014-2613-7 RETINAL DISORDERS Foveola nonpeeling internal limiting membrane surgery to prevent inner retinal damages in early stage 2 idiopathic macula hole Tzyy-Chang Ho & Chung-May Yang & Jen-Shang Huang & Chang-Hao Yang & Muh-Shy Chen Received: 29 October 2013 /Revised: 26 February 2014 /Accepted: 5 March 2014 # Springer-Verlag Berlin Heidelberg 2014 Abstract Keywords Fovea . Foveola . Internal limiting membrane . Purpose The purpose of this study was to investigate and macular hole . Müller cell . Vitrectomy present the results of a new vitrectomy technique to preserve the foveolar internal limiting membrane (ILM) during ILM peeling in early stage 2 macular holes (MH). Introduction Methods The medical records of 28 consecutive patients (28 eyes) with early stage 2 MH were retrospectively reviewed It is generally agreed that internal limiting membrane (ILM) and randomly divided into two groups by the extent of ILM peeling is important in achieving closure of macular holes peeing. Group 1: foveolar ILM nonpeeling group (14 eyes), (MH) [1]. An autopsy study of a patient who had undergone and group 2: total peeling of foveal ILM group (14 eyes). A successful MH closure showed an area of absent ILM sur- donut-shaped ILM was peeled off, leaving a 400-μm-diameter rounding the sealed MH [2]. ILM over foveola in group 1. The present ILM peeling surgery of idiopathic MH in- Results Smooth and symmetric umbo foveolar contour was cludes total removal of foveolar ILM. However, removal of restored without inner retinal dimpling in all eyes in group 1, all the ILM over the foveola causes anatomical changes of the but not in group 2.
    [Show full text]
  • Towards a Chromatic Pupillometry Protocol for Assessing Melanopsin-Driven Post-Illumination Pupil Response in Basic Science and Clinical Investigations
    TOWARDS A CHROMATIC PUPILLOMETRY PROTOCOL FOR ASSESSING MELANOPSIN-DRIVEN POST-ILLUMINATION PUPIL RESPONSE IN BASIC SCIENCE AND CLINICAL INVESTIGATIONS by Shaobo Lei A thesis submitted in conformity with the requirements for the degree of Master of Science Institute of Medical Science University of Toronto © Copyright by Shaobo Lei 2016 Towards a Chromatic Pupillometry Protocol for Assessing Melanopsin-Driven Post-Illumination Pupil Response in Basic Science and Clinical Investigations Shaobo Lei Master of Science Institute of Medical Science University of Toronto 2016 Abstract The pupillary light reflex (PLR) is mediated by intrinsically photosensitive retinal ganglions cells (ipRGCs), a sub-group of retinal ganglion cells that contain photopigment melanopsin. Melanopsin activation drives a sustained pupil constriction after the offset of light stimulus, this so-called post-illumination pupil response (PIPR) is an in vivo index of melanopsin-driven ipRGC photoactivity. PIPR can be assessed by chromatic pupillometry, but consensus on a standardized PIPR testing protocol has not been reached yet. The purpose of this thesis is to develop an optimized PIPR testing methodology, and to use it to investigate clinical and basic science questions related to melanopsin and ipRGCs. Based on previous pilot work on full-field chromatic pupillometry, a new and repeatable method was developed to measure PIPR induced by hemifield, central-field and full-field light stimulation. This chromatic pupillometry system was then used to investigate a series of basic science and clinical questions related to melanopsin and ipRGCs. ii Acknowledgments I would like to take this opportunity to express my gratitude to a number of people who have helped me to see through this thesis project.
    [Show full text]
  • Clinical Study of Etiopathogenesis of Isolated Oculomotor Nerve Palsy
    CLINICAL STUDY OF ETIOPATHOGENESIS OF ISOLATED OCULOMOTOR NERVE PALSY DISSERTATION SUBMITTED TO In partial fulfillment of the requirement for the degree of M.S. DEGREE EXAMINATION OF BRANCH III OPHTHALMOLOGY of THE TAMIL NADU DR. M. G. R MEDICAL UNIVERSITY CHENNAI- 600032 DEPARTMENT OF OPHTHALMOLOGY TIRUNELVELI MEDICAL COLLEGE TIRUNELVELI- 11 APRIL 2015 CERTIFICATE This is to certify that this dissertation entitled “Clinical Study Of Etiopathogenesis Of Isolated Oculomotor Nerve Palsy” submitted by Dr. Saranya.K.V to the faculty of Ophthalmology ,The Tamil Nadu Dr. MGR Medical University, Chennai in partial fulfillment of the requirement for the award of M.S Degree Branch III (Ophthalmology), is a bonafide research work carried out by her under my direct supervision and guidance. Dr. L.D.THULASI RAM MS. (Ortho) Dr A.YOGESWARI. The Dean Professor & Head of the Department Tirunelveli Medical College, Department of Ophthalmology Tirunelveli Tirunelveli Medical College, Tirunelveli. DECLARATION BY THE CANDIDATE I hereby declare that this dissertation entitled “Clinical Study Of Etiopathogenesis Of Isolated Oculomotor Nerve Palsy” is a bonafide and genuine research work carried out by me under the guidance of Dr. RITA HEPSI RANI .M, Assistant Professor of Ophthalmology, Department of Ophthalmology, Tirunelveli Medical College, Tirunelveli Dr. Saranya.K.V Post Graduate In Ophthalmology, Department Of Ophthalmology, Tirunelveli Medical College, Tirunelveli. ACKNOWLEDGEMENT I express my sincere gratitude and thanks to The Dean, Tirunelveli Medical College, Tirunelveli, for providing all the facilities to conduct this study. I sincerely thank Dr.A.Yogeswari Professor and HOD, Dept of Ophthalmology for her valuable advice, comments and constant encouragement for the completion of this study.
    [Show full text]
  • Retinal Anatomy and Histology
    1 Q Retinal Anatomy and Histology What is the difference between the retina and the neurosensory retina? 2 Q/A Retinal Anatomy and Histology What is the difference between the retina and the neurosensory retina? While often used interchangeably (including, on occasion, in this slide-set), these are technically not synonyms. The term neurosensory retina refers to the neural lining on the inside of the eye, whereas the term retina refers to this neural lining along with the retinal pigmentthree epithelium words (RPE). 3 A Retinal Anatomy and Histology What is the difference between the retina and the neurosensory retina? While often used interchangeably (including, on occasion, in this slide-set), these are technically not synonyms. The term neurosensory retina refers to the neural lining on the inside of the eye, whereas the term retina refers to this neural lining along with the retinal pigment epithelium (RPE). 4 Q Retinal Anatomy and Histology What is the difference between the retina and the neurosensory retina? While often used interchangeably (including, on occasion, in this slide-set), these are technically not synonyms. The term neurosensory retina refers to the neural lining on the inside of the eye, whereas the term retina refers to this neural lining along with the retinal pigment epithelium (RPE). The neurosensory retina contains three classes of cells—what are they? There are five types of neural elements—what are they? What are the three types of glial cells? The two vascular cell types? --? ----PRs ----Bipolar cells ----Ganglion cells ----Amacrine cells ----Horizontal cells --? ----Müeller cells ----Astrocytes ----Microglia --? ----Endothelial cells ----Pericytes 5 A Retinal Anatomy and Histology What is the difference between the retina and the neurosensory retina? While often used interchangeably (including, on occasion, in this slide-set), these are technically not synonyms.
    [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]
  • Pupils and Near Vision
    PUPILS AND NEAR VISION Akilesh Gokul PhD Research Fellow Department of Ophthalmology Iris Anatomy Two muscles: • Radially oriented dilator (actually a myo-epithelium) - like the spokes of a wagon wheel • Sphincter/constrictor Pupillary Reflex • Size of pupil determined by balance between parasympathetic and sympathetic input • Parasympathetic constricts the pupil via sphincter muscle • Sympathetic dilates the pupil via dilator muscle • Response to light mediated by parasympathetic; • Increased innervation = pupil constriction • Decreased innervation = pupil dilation Parasympathetic Pathway 1. Three major divisions of neurons: • Afferent division 2. • Interneuron division • Efferent division Near response: • Convergence 3. • Accommodation • Pupillary constriction Pupil Light Parasympathetic – Afferent Pathway 1. • Retinal ganglion cells travel via the optic nerve leaving the optic tracts 2. before the LGB, and synapse in the pre-tectal nucleus. 3. Pupil Light Parasympathetic – Efferent Pathway 1. • Pre-tectal nucleus nerve fibres partially decussate to innervate both Edinger- 2. Westphal (EW) nuclei. • E-W nucleus to ipsilateral ciliary ganglion. Fibres travel via inferior division of III cranial nerve to ciliary ganglion via nerve to inferior oblique muscle. 3. • Ciliary ganglion via short ciliary nerves to innervate sphincter pupillae muscle. Near response: 1. Increased accommodation Pupil 2. Convergence 3. Pupillary constriction Sympathetic pathway • From hypothalamus uncrossed fibres 1. down brainstem to terminate in ciliospinal centre
    [Show full text]
  • Anatomy & Physiology of The
    Anatomy & Physiology of The Eye 2017-2018 Done By: 433 Team Abdullah M. Khattab Important Doctor’s Notes Extra Abdullah AlOmair Resources: Team 433, Doctors Notes, Vaughan & Asbury’s General ophthalmology. Editing File Embryology of The Eye ............................................................................................. 2 ● Defects: ........................................................................................................................... 2 Development of The Eye After Birth .......................................................................... 3 ● Refractive power depends on two factors: ...................................................................... 3 The Orbit ................................................................................................................... 4 ● Seven bones contribute the bony orbit and surrounded by nasal sinuses. .................... 4 ● The orbital wall, pear-like shaped, formed by: ................................................................ 4 ● Structures Passing Through the Optic Openings: ........................................................... 4 Extraocular Muscles .................................................................................................. 1 ● Anatomy .......................................................................................................................... 1 ● Notes: .............................................................................................................................. 1 ● Field of action:
    [Show full text]
  • The Anatomy of the Foveola Reinvestigated
    A peer-reviewed version of this preprint was published in PeerJ on 12 March 2018. View the peer-reviewed version (peerj.com/articles/4482), which is the preferred citable publication unless you specifically need to cite this preprint. Tschulakow AV, Oltrup T, Bende T, Schmelzle S, Schraermeyer U. 2018. The anatomy of the foveola reinvestigated. PeerJ 6:e4482 https://doi.org/10.7717/peerj.4482 The anatomy of the foveola reinvestigated Alexander V. Tschulakow 1 , Theo Oltrup 2 , Thomas Bende 2 , Sebastian Schmelzle 3 , Ulrich Schraermeyer Corresp. 1, 4 1 Division of Experimental Vitreoretinal Surgery, University Hospital Tübingen, Centre for Ophthalmology, Tübingen, Germany 2 Division of Experimental Ophthalmic Surgery, University Hospital Tübingen, Centre for Ophthalmology, Tübingen, Germany 3 Ecological Networks, Department of Biology, Technische Universität Darmstadt, Darmstadt, Germany 4 Ocutox (www.ocutox.com), Hechingen, Germany Corresponding Author: Ulrich Schraermeyer Email address: [email protected] Objective. In the foveola of the eye, photoreceptors and Müller cells with a unique morphology have been described, but little is known about their 3D structure and orientation. Considering that there is an angle-dependent change in the foveolar photoreceptor response for the same light beam, known as the Stiles Crawford Effect of the first kind (SCE I), which is still not fully understood, a detailed analysis of the anatomy of the foveolar cells might help to clarify this phenomenon. Methods. Serial semithin and ultrathin sections, and focused ion beam (FIB) tomography were -prepared from 32 foveolae from monkeys (Macaca fascicularis) and humans. Foveolae were also analyzed under the electron microscope. Serial sections and FIB analysis were then used to construct 3D models of central Müller and photoreceptor cells.
    [Show full text]