Inflammatory Diseases of the Conjuctiva (eBook)

Thanh Hoang-Xuan, Catherine Creuzot-Garcher, Christophe Baudouin (Autoren)

eBook Download: EPUB

2001 | 1. Auflage
Georg Thieme Verlag KG
978-3-13-257871-5 (ISBN)

Infos

'A splendid book...material is presented beautifully...the illustrations are spectacular.' --C. Stephen Foster, MD, Professor of Ophthalmology, Harvard Medical School, Boston, Massachusetts 'I am very impressed by the quality of the presentations...it is simply a superb book.' --Claes H. Dohlman, MD, Professor of Ophthalmology, Harvard Medical School, Boston, Massachusetts As conjunctivitis is one of the most difficult eye disorders to treat and diagnose, Inflammatory Diseases of the Conjunctiva is an extremely valuable, problem-solving text for the practicing ophthalmologist. This new book provides outstanding guidance on diagnosing and managing all aspects of acute and chronic conjunctivitis, including a thorough understanding of the causes and basic mechanisms of the disorder. Beginning with a complete description of the functional anatomy of the conjunctiva, the book goes on to cover the major conjunctival inflammatory diseases, including acute infections, allergic, auto-immune, iatrogenic, chlamydial and others. Conjunctivitis associated with systemic inflammatory conditions such as Sjogren's syndrome or bullous mucocutaneous disease is also discussed. Key Features: Practical diagnosis and treatment tables, along with clear and helpful diagrams Over 200 superb, full-color illustrations Invaluable information on the management of inflammatory conditions of the conjunctiva An exhaustive bibliography While other books have addressed conjunctivitis in individual chapters, this is the most comprehensive publication available today. Highly praised by faculty at the prestigious Harvard Medical School, Inflammatory Diseases of the Conjunctiva is essential for anyone who works or teaches in the field of ophthalmology.

Thanh Hoang-Xuang, Christophe Baudouin, Catherine Creuzot-Garcher

Textauszug

Chapter 1 Anatomy

B. Kantelip and C. Creuzot-Garcher

Introduction

This chapter is a thorough analysis of conjunctival anatomy, zooming in from the lowest to the highest magnification.

The conjunctiva is a vascularized mucous membrane that covers the anterior surface of the eyeball and the posterior surface of the upper and lower eyelids. It is responsible for secreting the mucus required for tear film stability and corneal transparency. It also plays an important defensive role. It is richly vascularized and contains many immunocompetent cells capable of initiating and mediating inflammatory reactions, and of synthesizing immunoglobulin. The morphological characteristics (microvilli) and biochemical properties (enzyme activity) of conjunctival epithelial cells means that they can phagocytose foreign particles such as viruses.

Anatomy

The Conjunctiva1 (Fig. 1.1)

The Palpebral Conjunctiva

In continuity with the skin, the palpebral conjunctiva consists of three parts (Fig. 1.2):

—The mucocutaneous junction is located behind the row of meibomian gland openings. It is the transition zone between the stratified keratinizing squamous epithelium of the lid margin and the stratified nonkeratinizing squamous epithelium of the conjunctiva;

—The tarsal conjunctiva is strongly adherent to the tarsus;

—The orbital conjunctiva extends from the tarsal plate to the fornix.

The Conjunctival Cul-de-sac, or Fornix

This is the transition zone between the palpebral and bulbar conjunctivas.

—The superior fornix, which is the deepest, is situated at the level of the orbital rim, about 8-10 mm from the limbus:

Fig. 1.1 Diagrammatic representation of lid anatomy

Fig. 1.2 The lid margin represents the transition zone between the epidermis and the conjunctival epithelium. The meibomian glands are located in the tarsus (light microscopy, HES x 25)

Fig. 1.3 The structure of the serous glands is identical to that of the lacrimal glands. The serous glands are composed of acini formed by cylindrical secretory cells (light microscopy, HES x 400)

—The inferior fornix is 8 mm from the limbus;

—The lateral fornix is 14 mm from the limbus;

—On the medial side, there is no fornix, which is replaced by the caruncle and the plica semilunaris (a rudimentary third lid).

The Bulbar Conjunctiva

Thin and transparent, the bulbar conjunctiva consists of two parts:

—The scleral part extends from the conjunctival fornix to the limbus. It is readily cleavable, because it is separated from the Tenon capsule by subconjunctival connective tissue. The conjunctiva, the sclera, and the Tenon's capsule are firmly attached approximately 3 mm from the limbus, and the conjunctiva is more difficult to mobilize;

—The limbal part forms a ring about 3 mm wide at the junction between the conjunctival and corneal epithelia.

The Conjunctival Glands2,3 (Fig. 1.1)

These participate in tear film secretion. There are two groups of accessory conjunctival lacrimal glands, which differ according to the type of secretion (serous or mucous). The superficial lipid layer of the tear film is secreted by palpebral sebaceous glands known as meibomian (Fig. 1.2) and Zeiss glands.

Serous Glands (Fig. 1.3)

—Krause's glands are located in the deep conjunctival tissue of the superior fornix. There are about 40 such glands in the superior fornix and six to eight in the inferior fornix. Their histopathological aspect is identical to that of the orbital lacrimal glands;

—Wolfring's glands: between two and five Wolfring glands are found in the upper lid (along the upper edge of the tarsus), and another two are present along the lower edge of the inferior tarsus. Their excretory ducts are lined by cubic basal cells identical to those of the conjunctival epithelium.

Mucous Glands

Mucus is secreted by goblet cells present in the conjunctival epithelium and by structures with a glandular architecture (Henle's glands and Manz's glands).

—Henle's glands, or crypts, are situated on the upper edge of the superior tarsus. They correspond to epithelial invaginations within the chorion and are composed of goblet cells;

—Manz's glands, present in the limbus of many animal species, are absent in humans.2

Histology and Ultrastructure

General Architecture

The conjunctival epithelium is composed of between two and 8-10 layers of cells, according to the precise location. As in all mucous membranes, the epithelium comprises a single layer of basal cells, a variable number of layers of intermediate cells, and superficial cells of variable shape.

The flattening of the superficial cells appears to be an adaptation to mechanical pressure. Besides epithelial cells, the epithelium contains melanocytes with a morphology identical to that of cutaneous melanocytes (Fig. 1.4). They are located among the basals cells of the epithelium. Immunocom-petent cells (especially Langerhans cells) are also present within the epithelium. Their function is discussed in detail in Chapter 2.

The entity referred to as the conjunctival epithelium in fact has four distinct morphological components.

—The epithelium of the eyelid margin is a transition zone between the epidermis (keratinizing stratified squamous epithelium) and a nonkeratinizing stratified squamous epithelium with flattened superficial cells (Fig. 1.2);

—The conjunctival epithelium of the tarsal and bulbar conjunctivas is a stratified epithelium with more or less cylindrical superficial cells. In these two sites the epithelium gradually changes to resemble the epithelium of the fornix (Fig. 1.5);

—The conjunctival epithelium of the fornix is a stratified cylindrical epithelium (Fig. 1.6);

—The limbus is a particular transition zone between the conjunctival and corneal epithelia. It is covered by a stratified epithelium with flattened superficial cells (Fig. 1.7).

Fig. 1.4 Limbal conjunctival epithelium; note the melanocytes in the basal cell layer (light microscopy, Fontana-Masson staining x 400)

Fig. 1.5 Bulbar conjunctiva; the epithelial cells become cylindrical when they reach the surface. Note the abundant goblet cells (light microscopy, HES x 25)

Fig. 1.6 Forniceal conjunctiva; the superficial epithelial cells are cylindrical (light microscopy, semi-thin section, toluidine blue x 400)

Fig. 1.7 Limbal conjunctiva; the superficial cells have a squamous appearance; the chorion is thin (light microscopy, HES x 250)

 

The basement membrane zone (BMZ) separates the epithelium from the chorion or conjunctival stroma. Besides its key role in epithelial adhesion, it appears to have major antigenic potency, as reflected by its involvement in many autoimmune diseases (see Chapter 4).

Finally, the chorion, in addition to its collagen framework, possesses abundant vessels and immunocompetent cells, explaining the rapid and violent inflammatory reactions that can occur there. The cellular actors in these immunological responses and their corresponding cytokines will be examined in Chapter 2.

Epithelium

Basal Cells (Fig. 1.8a)

Basal cells have a cuboidal shape and form a single layer separated from the chorion by the BMZ, to which they are connected by hemidesmosomes and adhesion complexes. The lateral cell membranes possess abundant extensions into the intercellular spaces and are connected to one another by desmosomes. The cytoplasm of these cells contains bundles of intersecting tonofilaments corresponding to keratin fibers (Focus 1). The latter converge toward dense plaques formed by intracytoplasmic constituents of desmosomes and hemidesmosomes. The cellular organelles (mitochondria and rough endoplasmic reticulum) are mainly situated in a perinuclear space free of tonofilaments. Basal cells are undifferentiated and can divide. Breitbach and Spitznas4 observed about 10% light basal cells in paralimbal and juxtacaruncular sites, the remaining basal cells being described as dark. The cytoplasm of light basal cells is free of tonofilaments and contains many mitochondria grouped together at the apical part of the cell and characterized by a dense matrix and fine crests. These cells are not connected to neighboring cells by desmosomes.

Intermediate Cells (Fig. 1.8b)

This cell layer is only present in areas where the conjunctival epithelium is thickest (especially the limbus and fornix). The cells are interconnected by desmosomes, which are themselves connected to intracytoplasmic tonofilaments. Their cytoplasm contains intermediary filaments that measure 10 µm and are grouped together in bundles thinner than those found in basal cells. As in basal cells, the organelles are present in the clear perinuclear space and beneath the cytoplasmic membrane. The organelles include mitochondria, a rough ergastoplasmic reticulum, many polysomes, and, occasionally, a well-developed Golgi apparatus. In the juxtacaruncular location, Breitbach and Spitznas4 observed light cells (about 15%) within the layer of spinocytes, with little cytoplasm, no...

Produkt-Details

• Erscheint lt. Verlag: 28.3.2001
• Verlagsort: Stuttgart
• Sprache: englisch
• Themenwelt: Medizin / Pharmazie ► Medizinische Fachgebiete ► Augenheilkunde
• Schlagworte: Chronic Inflammation of the Conjunctiva • Hoang-Xuan • Ophthalmology
• ISBN-10: 3-13-257871-1 / 3132578711
• ISBN-13: 978-3-13-257871-5 / 9783132578715