opthalmic pathology-conjunctival-pathology

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  • 1.1Conjunctival pathology CHAPTER 4. CONJUCTIVAL PATHOLOGY Anatomy of the conjunctiva Denition: Thin mucous membrane lining the inner surface of the eyelid, and covers the anterior surface of the globe Gross picture: Parts: The conjunctiva is formed of five parts named according to related structures: Palpebral conjunctiva Marginal conjunctiva Transitional zone between skin and sulcus subtarsalis (Stratified squamous epithelium) Lacrimal puncti open in marginal conjunctiva Tarsal conjunctiva: vascular, tightly adherent to the back of the tarsus Fornical conjunctiva: Represents the reflection of the conjunctiva at the corners Four in numbers (superior, inferior, medial and lateral) Superior fornix is the deepest. It reaches the superior orbital margin at 8-10 mm from the limbus Inferior fornix extends 8 mm from the limbus. Superior and inferior fornices are adherent to expan- sions of from the sheaths of the levator and rectus muscles via areolar tissue. These adhesions deep- en the fornices Medial fornix is the shallowest Bulbar conjunctiva: Loose over the sclera It becomes firmly adherent to episclera within 3 mm from the limbus Plica semilunaris: Crescentic conjunctival fold at the inner canthus representing remnant of the nictitating membrane of animals The epithelium is nonkeratinized squamous with goblet cells Contains fatty tissue, skin appendages and accessory lacrimal glands Caruncle: Dense fibrovascular triangular elevation at the inner canthus covered by stratified squamous epithe- lium Represents a muco-cutaneous ovoid transition zone between conjunctival epithelium and the skin epidermis Contains hair, sebaceous and sweat glands, lobules of lacrimal gland and striated muscles Microscopic picture: Conjunctival epithelium: Origin: Surface ectoderm which also forms the epidermis of the skin, the corneal and lens epithelia Type: Nonkeratinized stratified squamous epithelium with goblet cells, which are abundant near the fornices Conjunctival melanocytes are found at the limbus, fornix, plica, caruncle and the sites of perforation of anterior ciliary vessels Langerhans cells: dendritic cells found mainly in tarsal conjunctiva, fornix and bulbar conjunctiva Accessory lacrimal glands: Glands of Krause: located in the deep conjunctival tissue in: Upper fornix: 42 in number Lower fornix: 6-8 in number IHAB-ch4_CS3ME.indd 1IHAB-ch4_CS3ME.indd 1 28-1-2009 13:46:2828-1-2009 13:46:28

2. Chapter 42 Their ductules unite into a single duct which opens in the fornix Glands of Wolfring: larger than glands of Krauze and located in: Above mid-superior tarsus: 2-5 in number Lower edge of inferior fornix: 2 in number Substantia propria: Loose connective tissue stroma with scattered lymphocytes (predominantly T-cells), lymphoid fol- licles (correspond to mucosa associated lymphoid follicles of the gut and bronchi), plasma cells and Langerhans cells (dendritic cells expressing class II antigen) Substantia propria of bulbar conjunctiva is loose and areolar, thus permitting chemosis. It contains a network of perilimbal capillaries giving nutrition to peripheral cornea Conjunctival cytology: Normal epithelium shows the following: Epithelial cells have a round nucleus and homogeneous cytoplasm Cells are flat squamous epithelial cells In smear, they appear cuboidal and clump in sheet Goblet cells: Contain clump of pale staining mucus containing flake shaped cells displacing the nu- cleus toward the edge of cell membrane giving the cell a signet-like ring appearance Epithelial abnormalities: Abnormal epithelium may be due to abnormal cellular morphology or pres- ence of abnormal cells. Abnormal epithelium can be obtained through impression cytology or exfolia- tive cytology (stained with Giemsa and Gram stain): Presence of polymorph nuclear leucocytes indicates bacterial conjunctivitis Presence of eosinophils suggests allergic conjunctivitis Presence of lymphocytes indicates viral conjunctivitis Presence of polymorph nuclear leucocytes, and lymphocytes points to Chlamydia trachomatis con- junctivitis with presence of basophilic intracytoplasmic inclusion bodies In alcohol fixed Pap stained smear, squamous dysplasia or malignancy is indicated by nuclear hyper- chromasia and high nuclear/cytoplasmic ratio and pleomorphism Vascular supply: Arterial supply: Posterior conjunctival arteries: Origin: Palpebral arteries from the tarsal arcades Distribution: Conjunctiva-limbus Anterior conjunctival arteries: Origin: Anterior ciliary arteries Distribution: Limbal conjunctiva Venous drainage: Anterior conjunctival veins drain into anterior ciliary veins Posterior conjunctival veins drain into palpebral veins Lymphatics: drain into the preauricular and submandibular lymph nodes Nerve supply: Same as palpebral nerve supply Long ciliary nerves supply the circumcorneal conjunctiva and cornea Vascular abnormalities 1. Hyperemia Primary: Active vasodilatation in response to inflammation IHAB-ch4_CS3ME.indd 2IHAB-ch4_CS3ME.indd 2 28-1-2009 13:46:2828-1-2009 13:46:28 3. 3Conjunctival pathology Secondary: Passive (vascular congestion due to venous obstruction): Space occupying orbital lesions Increased blood viscosity Active: increased filling of arterial system: Arterializations in carotid-cavernous fistula External carotid shunting in internal carotid occlusion Paroxysmal: associated with simultaneous lacrimation and rhinorrhea Charlins syndrome (migrainous nasociliary neuritis) Hortons cephalgia Sluders syndrome (neuralgia of the sphenopalatine ganglion) 2. Vascular sludging Increased blood viscosity or decreased circulatory velocity 3. Chemosis Edema due to increased permeability of conjunctival vessels 4. Subconjunctival hemorrhage Differential diagnosis: Idiopathic (spontaneous without sequelae) Traumatic Inflammation: Viral conjunctivitis Febrile illness Subacute bacterial endocarditis Trichinosis Vascular: Hypertension and arteriosclerosis Orbital stasis Hemorrhagic diathesis: vitamin C deficiency (scurvy) NB: Kaposis sarcoma can mimic subconjunctival hemorrhage 5. Telangiectasia Rendu-Osler-Weber syndrome Louis-Bar syndrome Fabrys disease Sturge-Weber syndrome 6. Microaneurysms Denition: Saccular dilatation of the capillary network Etiology: Diabetes Hypertension Arteriosclerosis Carotid occlusion Sickle hemoglobinopathy (Hb-SS disease): Patons sign: comma-shaped conjunctival microaneurysms IHAB-ch4_CS3ME.indd 3IHAB-ch4_CS3ME.indd 3 28-1-2009 13:46:2828-1-2009 13:46:28 4. Chapter 44 Congenital lesions 1. Cryptophthalmos 2. Epitarsus 3. Congenital ectropion 4. Congenital lymphedema 5. Hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber) 6. Epidermoid (see eyelid pathology section) 7. Congenital dermoid Denition: Choristoma formed of variety of tissues including fat, muscle, hair follicles, cartilage Etiology: Isolated finding Associated with syndromes: Goldenhar syndrome Treacher-Collins syndrome Nevus sebaceous of Jadassohn Pathology: Smooth yellowish subconjunctival nodules Inferotemporal quadrant Encroaching on cornea Dermoid are commonly solid and may be cystic Dermoids are formed of interweaving, coarsely thickened collagen fibers covered by skin-like epithe- lium Contains epidermal appendages (hair, sebaceous and sweat glands) 8. Dermolipomas Soft mobile subconjunctival nodules seen in adults superotemporal conjunctiva Choristoma of fat and connective tissue Can extend deep within orbit (should be excised carefully) 9. Complex choristoma Also contains cartilage, fat and lacrimal gland elements Immunological disorders with conjunctival findings 1. Ataxia telangiectasia (Louis-Bar syndrome) 2. Hereditary angioneurotic edema Autosomal dominant C1 esterase inhibitor deficiency 3. Toxic epidermal necrosis (Yells syndrome) 4. Weskit-Aldrich syndrome IHAB-ch4_CS3ME.indd 4IHAB-ch4_CS3ME.indd 4 28-1-2009 13:46:2828-1-2009 13:46:28 5. 5Conjunctival pathology Conjunctival inflammation 1. Acute conjunctivitis Denition: Acute self-limited infection of conjunctival surface of less than 3 weeks duration Etiology: Bacterial: Streptococcus pneumoniae Staphylococcus aureus Hemophilus influenza Pathology: Hyperemia, chemosis and purulent discharge Presence of polymorph nuclear leucocytes in substantia propria and epithelium Mucopurulent discharge Petechial hemorrhages Outcome: Resolution Chronicity Complications: Superficial crescentic marginal ulcer Iridocyclitis (pneumococci) 2. Purulent conjunctivitis Denition: An acute severe suppurative form of conjunctivitis with generalized manifestations Etiology: Forms: Purulent conjunctivitis of adults Ophthalmia neonatorum Onset: Explosive (few hours to few days) Organisms: Gram-negative cocci: Neisseria gonorrhea (60- 80%) Staphylococci Streptococci Gram-positive bacilli: Diphtheria Pathology: Massive purulent discharge Severe hyperemia and chemosis Eyelid edema Membrane formation Complications: Corneal ulceration: Gonococci invade corneal epithelium Keratitis: 15-40% Diffuse epithelial infiltration Marginal infiltrates Corneal ulcers: Marginal ulcer Ring ulcer Central ulcer IHAB-ch4_CS3ME.indd 5IHAB-ch4_CS3ME.indd 5 28-1-2009 13:46:2828-1-2009 13:46:28 6. Chapter 46 Iridocyclitis Spastic ectropion Chronicity 3. True membranous conjunctivitis Denition: Acute infective conjunctivitis characterized by true membrane formation Etiology: Organism: Corynebacterium diphtheria bacilli Age: 2-5 years Season: Winter Gonococcus Beta-hemolytic streptococci Stevens-Johnson syndrome Pathology: Characteristics of membrane: Formed as a result of toxin diffusion Composition: necrotic epithelium, exotoxin and diphtheria bacilli entangled in fibrin and dense neutro- phils Adherent to basement membrane Peeling results in a raw bleeding surface The underlying tissues are markedly congested and infiltrated with heavy neutrophils Lo

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