DOCSLIB.ORG

Pathology of the Cornea and Sclera

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Pathology of the Cornea and Sclera Pathology of the Cornea and Sclera Philippe Labelle, DVM, DACVP Antech Diagnostics 12th Biannual William Magrane Basic Science Course in Veterinary and Comparative Ophthalmology Cornea • Congenital/dystrophies/degenerations • Non-specific responses to injury • Keratitis • Specific infections/conditions General Considerations • Cornea has limited ways it responds to injury • Cornea has limited healing capacity (to maintain function) Dermoid • Ectopic island of skin on cornea (or conjunctiva) • Congenital choristoma • Has many or all features of normal skin • “Cutaneous metaplasia” is not analogous to a dermoid. Dermoid Courtesy UC Davis VMTH Ophthalmology Service Dermoid Courtesy of Dr. Chris Reilly Dermoid Hair follicle Thick pigmented epithelium Sebaceous glands Courtesy of Dr. Chris Reilly Corneal Dystrophy and Degeneration • Epithelial, stromal or endothelial • True dystrophy is bilateral and symmetric • Not associated with inflammatory or metabolic disease • Often breed-related/heritable • Degeneration: Lesions secondary to other diseases, not true dystrophies Corneal Epithelial Dystrophy • Shetland Sheepdogs; Longhaired Dachshunds • Superficial punctate corneal dystrophy • Dysplasia of basement membrane • Dyskeratosis and necrosis of epithelium • Unlikely to be biopsied Corneal Epithelial Dystrophy Corneal Epithelial Dystrophy Epithelial dystrophy in a Basilisk lizard H&E Deposition of excessive irregular PAS-positive, basement membrane material both on PAS the basal aspect of the epithelium and in the epithelium Courtesy of COPLOW Mineral/Band Keratopathy • Deposition of mineral in the basement membrane of the corneal epithelium and/or superficial stroma • Usually secondary (not a true dystrophy) • Inflammation and hypercalcemia are potential causes of secondary mineral deposition. • Horses (uveitis/ steroid and phosphate containing topical solutions) Mineral/Band Keratopathy • Calcareous degeneration: affects both the basement membrane area and the deep stroma; may be present in the absence of any other ocular disease • von Kossa stain highlights the phosphorus of the calcium-phosphorus complex. Alizarine Red specifically stains calcium Band Keratopathy Band Keratopathy Band Keratopathy Courtesy of Dr. Chris Reilly Stromal Lipid Dystrophy • “Corneal dystrophy” • Bilateral and symmetrical with no association to metabolic disease • Accumulation of lipids within the stroma • Macrophages may border these foci • Acquired lipid keratopathy can be associated with corneal or adjacent disease, or metabolic disease; typically well-vascularized Stromal Lipid Dystrophy • Lipids are dissolved during routine processing • Lipids appear as clear space/vacuoles/clefts • Cholesterol clefts angular or needle shaped clearings. It is one form of lipid accumulation • Special stains for lipid (Oil Red O, Sudan Black) can on be performed on fresh, frozen or fixed but unprocessed sections Lipid/Cholesterol Dystrophy Lipid dystrophy Courtesy of Dr. Chris Reilly Lipid Dystrophy/Keratopathy Courtesy of COPLOW Lipid Dystrophy/Keratopathy Oil Red O, Courtesy of COPLOW Lipid Dystrophy Courtesy of Dr. Brian Stacy, UCDavis Endothelial Dystrophy • Most often secondary (not true dystrophy) • Primary in Boston terrier, Chihuahua • Initially affects the temporal cornea • Leads to corneal edema +/- ulceration • Endothelial cell attenuation Endothelial Dystrophy • Formalin fixation can cause artifactual vacuolation of the endothelium • Anterior uveitis, glaucoma, surgery, anterior lens luxation, are possible causes of endothelial degeneration • Fibrometaplasia, retrocorneal membranes may be present with endothelial degeneration • The endothelium can slide but cannot replicate (post-miotic) with rare exceptions (rabbits +\- dogs). Endothelial Dystrophy Cornea • Congenital/dystrophies/degenerations • Non-specific responses to injury • Keratitis • Specific infections/conditions Inclusion cysts, epithelial downgrowth • Cysts • Congenital or traumatic • Often secondary to surgery • Epithelial downgrowth • Trauma, ulceration Inclusion cyst Epithelial downgrowth Courtesy of COPLOW Epithelial downgrowth Courtesy of Dr. Chris Reilly Epithelial Downgrowth Epithelial Downgrowth Descemet’s Duplication • Double layer of basement membrane • Relatively common • Trauma, lens luxation, glaucoma, surgery are possible causes • May accompany breaks in Descemet’s membrane • There may be endothelium lining one or both layers • Unclear significance unless associated with extension on the iris or traumatic lesions elsewhere • Kafarnik et al. Vet Path 2009 Descemet’s Duplication Courtesy of Dr. Chris Reilly Descemet’s Duplication Descemet’s Duplication Descemet’s Duplication Endothelial Pigment • Secondary to release of uveal pigment • Neoplasia, inflammation, anterior synechia, ruptured uveal cyst, iris-cornea PPM • Does not appear to affect function (not associated with corneal edema) Endothelial Pigment Cornea • Congenital/dystrophies/degenerations • Non-specific responses to injury • Keratitis • Specific infections/conditions Keratitis, General Considerations • Ulcerative vs non-ulcerative • Inflammatory cellular infiltrate • Acute = neutrophils • Chronic= lymphoplasmacytic • Corneal edema • Stromal neovascularization Corneal edema • Loss of normal lamellar arrangement of the stroma • Must be differentiated from fixation artifact causing separation of lamellae Corneal edema Edema Artifact Courtesy of Dr. Chris Reilly Corneal edema Keratitis/Stromal Neovascularization • Begins 48-72 hours after injury • Progresses up to 1mm/24h. Keratitis/Stromal Neovascularization Courtesy of Dr. Chris Reilly Ulcerative keratitis • Ulcerative keratitis • SCCED • Ulcerative keratitis with keratomalacia (melting ulcers) Ulcerative keratitis • Epithelial changes in the remaining epithelium include sliding, rounding of the epithelial edges, hyperplasia • Neutrophils predominate in acute cases • Lymphoplasmacytic infiltration, stromal fibrosis and neovascularization with chronicity Ulcerative keratitis Ulcerative keratitis Ulcerative keratitis Ulcerative keratitis Ulcerative keratitis Ulcerative Keratitis with Keratomalacia • Melting ulcer • Horses, dogs (brachycephalic) +\- cats • Degeneration of stromal collagen • Metalloproteinases, serine proteases • Endogenous (inflammation/neutrophils) • Exogenous (some bacteria and fungi produce proteases) Ulcerative Keratitis with Keratomalacia Ulcerative Keratitis with Keratomalacia Courtesy of Dr. Chris Reilly Ulcerative Keratitis with Keratomalacia Courtesy of Dr. Chris Reilly Chronic Keratitis (Nonspecific) • “Chronic keratitis, superficial” • End result of a variety of corneal insults • It is not a disease, but a response pattern • Buphthalmos, lagophthalmos/exophthalmos, neurogenic disorders, lacrimal/Meibomian disorders (KCS), irritation from a mass or eyelid issue • Frequent in enucleated globes • Severe cases may mimic Chronic Superficial Keratitis/Pannus Chronic Keratitis (Nonspecific) • Epithelial lesions (hyperplasia, pigmentation +\- keratinization) • Lymphoplasmacytic inflammation • Pigmentary incontinence (leakage of melanin) • Stromal fibrosis and neovascularization Chronic Keratitis (Nonspecific) Chronic Keratitis (Nonspecific) Chronic Keratitis (Nonspecific) Chronic Keratitis (Nonspecific) Cornea • Congenital/dystrophies/degenerations • Non-specific responses to injury • Keratitis • Specific infections/conditions Chronic Superficial Keratitis (Pannus) • Immune mediated • German shepherds and sighthounds • Chronic lichenoid lymphoplasmacytic inflammation • Stromal fibrosis and neovascularization • Epithelial lesions (hyperplasia, pigmentation +\- keratinization) • Unlikely to be biopsied Chronic Superficial Keratitis/Pannus Chronic Superficial Keratitis/Pannus Chronic Superficial Keratitis (Pannus) Courtesy of Dr. Chris Reilly Spontaneous Chronic Corneal Epithelial Defects (SCCEDs) • Dogs (Boxers), cats, horses • Separation of the epithelium and stroma results in erosion/ulceration • Separated epithelium shows dysmaturation with loss of organized layering • Thin, acellular, hyalinized band in the superficial stroma • Murphy et al, IOVS, 2001; Bentley et al, IOVS, 2002; Gosling et al, VO, 2013; Hempstead JE et al VO, 2014. SCCED Courtesy of Dr. Chris Reilly SCCED Courtesy of Dr. Chris Reilly SCCED * Corneal Sequestrum • Cats (Persians) +\- horses, dogs • Well-circumscribed area of stromal devitalization, often with pigmentation • Some are not overtly pigmented • Acellular/devitalized/necrosis • Inflammation and neovascularization only at the periphery • Ulceration Corneal Sequestrum • Melanin? Iron? Porphyrins? • Association of feline herpesvirus in some studies, not in others • Stiles et al, AJVR 1997 • Nassisse et al, AJVR 1998 • Ejima et al, Science 1993 • Featherstone et al, VO, 2004 • Cullen et al, VO 2005 • Newkirk et al, VO, 2011 Corneal Sequestrum Corneal Sequestrum Courtesy of Dr. Chris Reilly Corneal Sequestrum Courtesy of COPLOW Corneal Sequestrum (dog) Florida Keratopathy • Florida spots • No convincing histologic lesions • Material in the picture in G5 may be acid fast positive; not acid-fast bacteria • Sarfaty (ECVO 2008) suggests fire ants Fungal Keratitis • Horses +\- dogs, rarely cats • Neutrophils +\- keratomalacia +\- stromal abscess • Ulceration • Fungal hyphae may be numerous or rare • Fungal hyphae are mostly in the deep stroma • Fungal hyphae may invade Descemet’s membrane • Aspergillus spp, Fusarium spp. • Opportunistic fungal colinization of injured corneas will be only superficial Fungal Keratitis Equine Fungal
Load more

Recommended publications
  • Symptoms of Age Related Macular Degeneration
    WHAT IS MACULAR DEGENERATION? wavy or crooked, visual distortions, doorway and the choroid are interrupted causing waste or street signs seem bowed, or objects may deposits to form. Lacking proper nutrients, the light- Age related macular degeneration (AMD) is appear smaller or farther away than they sensitive cells of the macula become damaged. a disease that may either suddenly or gradually should, decrease in or loss of central vision, and The damaged cells can no longer send normal destroy the macula’s ability to maintain sharp, a central blurry spot. signals from the macula through the optic nerve to central vision. Interestingly, one’s peripheral or DRY: Progression with dry AMD is typically slower your brain, and consequently your vision becomes side vision remains unaffected. AMD is the leading de-gradation of central vision: need for increasingly blurred cause of “legal blindness” in the United States for bright illumination for reading or near work, diffi culty In either form of AMD, your vision may remain fi ne persons over 65 years of age. AMD is present in adapting to low levels of illumination, worsening blur in one eye up to several years even while the other approximately 10 percent of the population over of printed words, decreased intensity or brightness of eye’s vision has degraded. Most patients don’t the age of 52 and in up to 33 percent of individuals colors, diffi culty recognizing faces, gradual increase realize that one eye’s vision has been severely older than 75. The macula allows alone gives us the in the haziness of overall vision, and a profound drop reduced because your brain compensates the bad ability to have: sharp vision, clear vision, color vision, in your central vision acuity.
    [Show full text]
  • Permeability of the Retina and RPE-Choroid-Sclera to Three Ophthalmic Drugs and the Associated Factors
    pharmaceutics Article Permeability of the Retina and RPE-Choroid-Sclera to Three Ophthalmic Drugs and the Associated Factors Hyeong Min Kim 1,†, Hyounkoo Han 2,†, Hye Kyoung Hong 1, Ji Hyun Park 1, Kyu Hyung Park 1, Hyuncheol Kim 2,* and Se Joon Woo 1,* 1 Department of Ophthalmology, Seoul National University College of Medicine, Seoul National University Bundang Hospital, Seongnam 13620, Korea; [email protected] (H.M.K.); [email protected] (H.K.H.); [email protected] (J.H.P.); [email protected] (K.H.P.) 2 Department of Chemical and Biomolecular Engineering, Sogang University, Seoul 04107, Korea; [email protected] * Correspondence: [email protected] (H.K.); [email protected] (S.J.W.); Tel.: +82-2-705-8922 (H.K.); +82-31-787-7377 (S.J.W.); Fax: +82-2-3273-0331 (H.K.); +82-31-787-4057 (S.J.W.) † These authors contributed equally to this work. Abstract: In this study, Retina-RPE-Choroid-Sclera (RCS) and RPE-Choroid-Sclera (CS) were prepared by scraping them off neural retina, and using the Ussing chamber we measured the average time– concentration values in the acceptor chamber across five isolated rabbit tissues for each drug molecule. We determined the outward direction permeability of the RCS and CS and calculated the neural retina permeability. The permeability coefficients of RCS and CS were as follows: ganciclovir, 13.78 ± 5.82 and 23.22 ± 9.74; brimonidine, 15.34 ± 7.64 and 31.56 ± 12.46; bevacizumab, 0.0136 ± 0.0059 and 0.0612 ± 0.0264 (×10−6 cm/s).
    [Show full text]
  • The Sclera C
    The Sclera c. Stephen Foster Maite Sainz de la Maza The Sclera Foreword by Frederick A. lakobiec With 134 Illustrations and 33 Color Plates Springer Science+Business Media, LLC C. Stephen Foster, MD Associate Professor of Ophthalmology Harvard Medical School Director, Immunology and Uveitis Service Massachusetts Eye and Ear Infirmary Boston, MA 02114 USA Maite Sainz de la Maza, MD, PhD Assistant Professor of Ophthalmology Central University of Barcelona 08036 Barcelona Spain Cover illustration: The eye of a patient with rheumatoid arthritis who has developed pro­ gressively destructive necrotizing scleritis. Library of Congress Cataloging-in-Publication Data Foster, C. Stephen (Charles Stephen), 1942- The sclera/C. Stephen Foster and Maite Sainz de la Maza. p. cm. Includes bibliographical references and index. ISBN 978-1-4757-2345-8 ISBN 978-1-4757-2343-4 (eBook) DOI 10.1007/978-1-4757-2343-4 1. Sclera-Diseases. I. Maza, Maite Sainz de lao II. Title. [DNLM: 1. Scleritis. 2. Sclera. WW 230 F754s 1993] RE328.F67 1993 617.7' 19-dc20 DNLMIDLC for Library of Congress 93-10235 Printed on acid-free paper. © 1994 Springer Science+ Business Media New York Originally published by Springer-Verlag New York, Inc. in 1994 Softcover reprint of the hardcover 1st edition 1994 All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher, Springer Science+Business Media, LLC. except for brief excerpts in connection with reviews or, scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden.
    [Show full text]
  • Cultivating a Cure for Blindness
    news and views were taken in a l-mm2 biopsy from the good eye, then they were cultured and, on second Cultivating a cure passage, they formed a tightly packed and communicating (confluent) monolayer of cells. For grafting, the conjunctiva! epi­ for blindness thelium was completely removed from the cornea and limbus of the recipient eye, and replaced with a slightly larger monolayer of Stuart Hodson cultured limbal epithelium. The eyes were Damaged corneas can often be repaired using donor grafts, but if the then covered with therapeutic soft contact damage is too great the graft wlll be rejected. This may change with the lenses, and tightly patched for several days. development of a method to Inhibit rejection which uses cultivated cells. The results after the limbal epithelial graft were very promising. The grafted epithelium he human cornea has a special proper­ epithelium can mould a smooth apical and was stable, transparent, multi-layered and Tty known as immune privilege, which basal surface, the limbal epithelial stem cells smooth. One of the patients had suffered an allows tissue grafts from donors to be do not form such a smooth surface. alkali burn to his left eye ten years earlier, and carried out without the usual problems of If the corneal epithelium is lost it can be had undergone three previous unsuccessful immune rejection. However, immune privi­ functionally regenerated by the limbal stem corneal grafts. Before the treatment he had lege is lost at the perimeter of the cornea - cells. But if both the corneal and limbal continual severe corneal vascularization the limb us of the eye - where the transpar­ epithelia are lost, the corneal surface is re­ ( development of blood vessels) and persis­ ent corneal stroma meets the opaque sclera colonized by the other neighbour of the tent ulceration, and the eye was painful and (Fig.
    [Show full text]
  • Quantitative Assessment of Central and Limbal Epithelium After Long
    Eye (2016) 30, 979–986 © 2016 Macmillan Publishers Limited All rights reserved 0950-222X/16 www.nature.com/eye 1,5 1,5 1 Quantitative RK Prakasam , BS Kowtharapu , K Falke , CLINICAL STUDY K Winter2,3, D Diedrich4, A Glass4, A Jünemann1, assessment of central RF Guthoff1 and O Stachs1 and limbal epithelium after long-term wear of soft contact lenses and in patients with dry eyes: a pilot study Abstract Purpose Analysis of microstructural Eye (2016) 30, 979–986; doi:10.1038/eye.2016.58; alterations of corneal and limbal epithelial published online 22 April 2016 cells in healthy human corneas and in other ocular conditions. Introduction Patients and methods Unilateral eyes of three groups of subjects include healthy The X, Y, Z hypothesis1 explains cell mechanism volunteers (G1, n = 5), contact lens wearers that is essential for the renewal and maintenance 1Department of (G2, n = 5), and patients with dry eyes of the corneal epithelium. This hypothesis Ophthalmology, University = proposes that the loss of corneal epithelial of Rostock, Rostock, (G3, n 5) were studied. Imaging of basal Germany (BC) and intermediate (IC) epithelial cells surface cells (Z) can be maintained by the from central cornea (CC), corneal limbus proliferation of basal epithelial cells (X), and the 2Faculty of Medicine, centripetal movements of the peripheral (CL) and scleral limbus (SL) was obtained by Institute of Anatomy, epithelial cells (Y). By utilizing this mechanism, University of Leipzig, in vivo confocal microscopy (IVCM). An it is also possible to categorize both disease and Leipzig, Germany appropriate image analysis algorithm was therapies according to the specific component 3 used to quantify morphometric parameters involved.1 Therefore it is vital to understand the Institute for Medical including mean cell area, compactness, Informatics, Statistics and cellular structures of both central and limbal Epidemiology (IMISE), solidity, major and minor diameter, and epithelial cells in normal and in various corneal University of Leipzig, maximum boundary distance.
    [Show full text]
  • Development of in Vitro Corneal Models: Opportunity for Pharmacological Testing
    Review Development of In Vitro Corneal Models: Opportunity for Pharmacological Testing Valentina Citi 1, Eugenia Piragine 1, Simone Brogi 1,* , Sara Ottino 2 and Vincenzo Calderone 1 1 Department of Pharmacy, University of Pisa, Via Bonanno 6, 56126 Pisa, Italy; [email protected] (V.C.); [email protected] (E.P.); [email protected] (V.C.) 2 Farmigea S.p.A., Via G.B. Oliva 6/8, 56121 Pisa, Italy; [email protected] * Correspondence: [email protected]; Tel.: +39-050-2219-613 Received: 24 October 2020; Accepted: 30 October 2020; Published: 2 November 2020 Abstract: The human eye is a specialized organ with a complex anatomy and physiology, because it is characterized by different cell types with specific physiological functions. Given the complexity of the eye, ocular tissues are finely organized and orchestrated. In the last few years, many in vitro models have been developed in order to meet the 3Rs principle (Replacement, Reduction and Refinement) for eye toxicity testing. This procedure is highly necessary to ensure that the risks associated with ophthalmic products meet appropriate safety criteria. In vitro preclinical testing is now a well-established practice of significant importance for evaluating the efficacy and safety of cosmetic, pharmaceutical, and nutraceutical products. Along with in vitro testing, also computational procedures, herein described, for evaluating the pharmacological profile of potential ocular drug candidates including their toxicity, are in rapid expansion. In this review, the ocular cell types and functionality are described, providing an overview about the scientific challenge for the development of three-dimensional (3D) in vitro models.
    [Show full text]
  • Topical Serum for Treatment of Keratomalacia
    PROCEDURES PRO > OPHTHALMOLOGY > PEER REVIEWED Topical Serum for Treatment of Keratomalacia Amy Knollinger, DVM, DACVO Eye Care for Animals Salt Lake City, Utah Corneal Anatomy An understanding of corneal anatomy is vital to determine if serum therapy for the treatment of keratomalacia should be initiated. The cornea makes up the anterior por- tion of the globe and provides multiple functions for vision: it is transparent (despite originating from surface ectoderm), thereby allowing for clear vision; it acts as the major refractive (bending of light) surface of the globe; and it provides a protective barrier between the globe and the environment The cornea consists of 4 layers in domestic species, being approximately 0.45–0.55 mm thick in the normal dog. The corneal epithelium is the most external layer overly- What You Will Need ing the stromal layer, which accounts for 90% of the total corneal thickness. The cor- n Sterile gloves neal epithelium in the dog and cat is 5–11 cells thick and has a turnover rate of n approximately 7 days.1 The stroma is made up of collagen fibers, which are precisely Clean #40 clipper blade arranged in parallel sheets running the entire diameter of the cornea, allowing for its n Chlorhexidine scrub and solution transparency. The third layer is an acellular membrane (ie, Descemet’s membrane), n Sterile needle and syringe which forms the basement membrane for the innermost layer, the endothelium. The n corneal endothelium is a single layer of hexagonally shaped cells forming the internal Red top sterile blood collection or barrier between the anterior chamber and the cornea.2 serum separator tube n Centrifuge Corneal Disease n Sterile pipette Corneal ulcers are classified by underlying cause.
    [Show full text]
  • Extraocular Muscles Orbital Muscles
    EXTRAOCULAR MUSCLES ORBITAL MUSCLES INTRA- EXTRA- OCULAR OCULAR CILIARY MUSCLES INVOLUNTARY VOLUNTARY 1.Superior tarsal muscle. 1.Levator Palpebrae Superioris 2.Inferior tarsal muscle 2.Superior rectus 3.Inferior rectus 4.Medial rectus 5.Lateral rectus 6.Superior oblique 7.Inferior oblique LEVATOR PALPEBRAE SUPERIORIOS Origin- Inferior surface of lesser wing of sphenoid. Insertion- Upper lamina (Voluntary) - Anterior surface of superior tarsus & skin of upper eyelid. Middle lamina (Involuntary) - Superior margin of superior tarsus. (Superior Tarsus Muscle / Muller muscle) Lower lamina (Involuntary) - Superior conjunctival fornix Nerve Supply :- Voluntary part – Oculomotor Nerve Involuntary part – Sympathetic ACTION :- Elevation of upper eye lid C/S :- Drooping of upper eyelid. Congenital ptosis due to localized myogenic dysgenesis Complete ptosis - Injury to occulomotor nerve. Partial ptosis - disruption of postganglionic sympathetic fibres from superior cervical sympathetic ganglion. Extra ocular Muscles : Origin Levator palpebrae superioris Superior Oblique Superior Rectus Lateral Rectus Medial Rectus Inferior Oblique Inferior Rectus RECTUS MUSCLES : ORIGIN • Arises from a common tendinous ring knows as ANNULUS OF ZINN • Common ring of connective tissue • Anterior to optic foramen • Forms a muscle cone Clinical Significance Retrobulbar neuritis ○ Origin of SUPERIOR AND MEDIAL RECTUS are closely attached to the dural sheath of the optic nerve, which leads to pain during upward & inward movements of the globe. Thyroid orbitopathy ○ Medial & Inf.rectus thicken. especially near the orbital apex - compression of the optic nerve as it enters the optic canal adjacent to the body of the sphenoid bone. Ophthalmoplegia ○ Proptosis occur due to muscle laxity. Medial Rectus Superior Rectus Origin :- Superior limb of the tendonous ring, and optic nerve sheath.
    [Show full text]
  • The Eye Is a Natural Optical Tool
    KEY CONCEPT The eye is a natural optical tool. BEFORE, you learned NOW, you will learn •Mirrors and lenses focus light • How the eye depends on to form images natural lenses •Mirrors and lenses can alter • How artificial lenses can be images in useful ways used to correct vision problems VOCABULARY EXPLORE Focusing Vision cornea p. 607 How does the eye focus an image? pupil p. 607 retina p. 607 PROCEDURE 1 Position yourself so you can see an object about 6 meters (20 feet) away. 2 Close one eye, hold up your index finger, and bring it as close to your open eye as you can while keeping the finger clearly in focus. 3 Keeping your finger in place, look just to the side at the more distant object and focus your eye on it. 4 Without looking away from the more distant object, observe your finger. WHAT DO YOU THINK? • How does the nearby object look when you are focusing on something distant? • What might be happening in your eye to cause this change in the nearby object? The eye gathers and focuses light. The eyes of human beings and many other animals are natural optical tools that process visible light. Eyes transmit light, refract light, and respond to different wavelengths of light. Eyes contain natural lenses that focus images of objects. Eyes convert the energy of light waves into signals that can be sent to the brain. The brain interprets these signals as shape, brightness, and color. Altogether, these processes make vision possible. In this section, you will learn how the eye works.
    [Show full text]
  • Vocabulario De Morfoloxía, Anatomía E Citoloxía Veterinaria
    Vocabulario de Morfoloxía, anatomía e citoloxía veterinaria (galego-español-inglés) Servizo de Normalización Lingüística Universidade de Santiago de Compostela COLECCIÓN VOCABULARIOS TEMÁTICOS N.º 4 SERVIZO DE NORMALIZACIÓN LINGÜÍSTICA Vocabulario de Morfoloxía, anatomía e citoloxía veterinaria (galego-español-inglés) 2008 UNIVERSIDADE DE SANTIAGO DE COMPOSTELA VOCABULARIO de morfoloxía, anatomía e citoloxía veterinaria : (galego-español- inglés) / coordinador Xusto A. Rodríguez Río, Servizo de Normalización Lingüística ; autores Matilde Lombardero Fernández ... [et al.]. – Santiago de Compostela : Universidade de Santiago de Compostela, Servizo de Publicacións e Intercambio Científico, 2008. – 369 p. ; 21 cm. – (Vocabularios temáticos ; 4). - D.L. C 2458-2008. – ISBN 978-84-9887-018-3 1.Medicina �������������������������������������������������������������������������veterinaria-Diccionarios�������������������������������������������������. 2.Galego (Lingua)-Glosarios, vocabularios, etc. políglotas. I.Lombardero Fernández, Matilde. II.Rodríguez Rio, Xusto A. coord. III. Universidade de Santiago de Compostela. Servizo de Normalización Lingüística, coord. IV.Universidade de Santiago de Compostela. Servizo de Publicacións e Intercambio Científico, ed. V.Serie. 591.4(038)=699=60=20 Coordinador Xusto A. Rodríguez Río (Área de Terminoloxía. Servizo de Normalización Lingüística. Universidade de Santiago de Compostela) Autoras/res Matilde Lombardero Fernández (doutora en Veterinaria e profesora do Departamento de Anatomía e Produción Animal.
    [Show full text]
  • The Complexity and Origins of the Human Eye: a Brief Study on the Anatomy, Physiology, and Origin of the Eye
    Running Head: THE COMPLEX HUMAN EYE 1 The Complexity and Origins of the Human Eye: A Brief Study on the Anatomy, Physiology, and Origin of the Eye Evan Sebastian A Senior Thesis submitted in partial fulfillment of the requirements for graduation in the Honors Program Liberty University Spring 2010 THE COMPLEX HUMAN EYE 2 Acceptance of Senior Honors Thesis This Senior Honors Thesis is accepted in partial fulfillment of the requirements for graduation from the Honors Program of Liberty University. ______________________________ David A. Titcomb, PT, DPT Thesis Chair ______________________________ David DeWitt, Ph.D. Committee Member ______________________________ Garth McGibbon, M.S. Committee Member ______________________________ Marilyn Gadomski, Ph.D. Assistant Honors Director ______________________________ Date THE COMPLEX HUMAN EYE 3 Abstract The human eye has been the cause of much controversy in regards to its complexity and how the human eye came to be. Through following and discussing the anatomical and physiological functions of the eye, a better understanding of the argument of origins can be seen. The anatomy of the human eye and its many functions are clearly seen, through its complexity. When observing the intricacy of vision and all of the different aspects and connections, it does seem that the human eye is a miracle, no matter its origins. Major biological functions and processes occurring in the retina show the intensity of the eye’s intricacy. After viewing the eye and reviewing its anatomical and physiological domain, arguments regarding its origins are more clearly seen and understood. Evolutionary theory, in terms of Darwin’s thoughts, theorized fossilization of animals, computer simulations of eye evolution, and new research on supposed prior genes occurring in lower life forms leading to human life.
    [Show full text]
  • JMSCR Vol||08||Issue||02||Page 208-210||February 2020
    JMSCR Vol||08||Issue||02||Page 208-210||February 2020 http://jmscr.igmpublication.org/home/ ISSN (e)-2347-176x ISSN (p) 2455-0450 DOI: https://dx.doi.org/10.18535/jmscr/v8i2.40 Keratomalacia - A Case Report Authors Deepthi Pullepu1*, Deepthi Janga2, V Murali Krishna3 *Corresponding Author Deepthi Pullepu Department of Ophthalmology, Rangaraya Medical College, Kakinada, Andhra Pradesh, India Abstract Xerophthalmia refers to an ocular condition of destructive dryness of conjunctiva and cornea caused due to severe vitamin A deficiency. Usually affects infants, children and women of reproductive age group. It is estimated to affect about one-third of children under the age of five around the world. Keratomalacia means dry and cloudy cornea which melts and perforates, caused due to severe vitamin A deficiency. Here we describe a case of 21 year old female with neurofibromatosis type 1 presenting with keratomalacia. Keywords: Vitamin A deficiency, Xerophthalmia, Keratomalacia. Introduction blindness is a significant contributor Vitamin A is essential for the functioning of the In India, it is estimated that there are immune system, healthy growth and development approximately 6.8 million people who have vision of body and is usually acquired through diet. less than 6/60 in at least one eye due to corneal Globally, 190 million children under five years of diseases; of these, about a million have bilateral age are affected by vitamin A deficiency involvement. They suffer from an increased risk of visual Corneal blindness resulting due to this disease can impairment, illness and death from childhood be completely prevented by institution of effective infections such as measles and those causing preventive or prophylactic measures at the diarrhoea community level.
    [Show full text]