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Conjunctiva 1
 

Conjunctiva 1

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  • Electron Microscopy

Conjunctiva 1 Conjunctiva 1 Presentation Transcript

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    • Conjunctiva (named because it conjoins the eyeball to the lids) is a thin, transparent mucous membrane that lines the posterior surface of the lids, and is then reflected forwards on the eye.
    • Conjunctiva is continuous anteriorly with the epithelium of the cornea.
    • Recessed in the eyelids, the conjunctiva forms a cul de sac, which is open in front at the palpebral fissure, and only closed when the eyes are shut.
    • Although all parts of the conjunctiva are continuous each has been given its own name to emphasize anatomic differences.
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    • Palpebral : The palpebral portion lines the eyelids; starts at the mucocutaneous junction of the lid margins and is firmly adherent to the tarsal plates. Subdivided into :
      • The marginal zone transitions between skin and conjunctiva and shows minimal keratinization.
      • The tarsal conjunctiva is a fairly flat layer.
      • The orbital zone shows more numerous Goblet cells.
    • Bulbar : that portion joining the eyeball is the bulbar conjunctiva. It covers the anterior sclera. The stroma of the bulbar conjunctiva is loosely attached to the underlying Tenon capsule, except at the limbus, where the attachment is form.
    • Forniceal : that forming the conjunctival sac and reflecting on the eye is called the fornix. It is loose and redundant so that it swells easily and may be thrown into folds.
    • 1. The conjunctival epithelium :
      • 2 – 5 cell layers thick.
      • Basal cuboidal cells evolve into flattened polyhedral cells as they reach the surface.
      • With chronic exposure and drying, the epithelium may become keratinized.
    • 2. The stroma (substantia propria) :
      • Richly vascularized connective tissue, separated from the epithelium by a basement membrane .
      • The adenoid superficial layer does not develop until about 3 months after birth, hence inability of the newborn to produce a follicular conjunctival reaction.
      • The deep, thicker fibrous layer is continous with the tarsal plates and belongs to the subconjuntival tissues rather than the conjunctiva.
    • Glands :
    • 1. Mucin secretors :
      • a. Goblet cells : located within epithelium, are most dense inferonasally
      • b. Crypts of Henle : are located along the upper third of the superior tarsal conjunctiva and along the lower third of the inferior tarsal conjunctiva.
      • c. Glands of Manz : encircle the limbus.
    • 2. Accessory Lacrimal Glands : of Krause and Wolfring are located deep within the substantia propria.
    • Destructive disorders of the conjunctiva such as cicatricial pemphigoid frequently damage the mucin secretors, whereas chronic inflammatory disorders may be associated with an increase in number of goblet cells.
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  • Tarsal conjunctiva Forniceal conjunctiva Electron Microscopy
  • The conjunctiva contains specialized folds or bumps called the plica semilunaris and caruncle. The plica semilunaris lining contains Goblet cells while the caruncle may have hair, sebaceous glands emanating from the surface.
    • Clinical features relevant to the differential diagnosis of conjunctival inflammation are :
    • A. symptoms
    • B. discharge
    • C. conjunctival reaction
    • D. membranes
    • E. lymphadenopathy
    • 1. Non-specific symptoms : lacrimation, irritation, stinging, burning, photophobia
    • 2. Pain and foreign body sensation – suggest corneal involvement
    • 3. Itching – hallmark of allergic conjunctivitis although it may also occur in blepharitis and keratoconjunctivitis sicca
    • Composed of exudate that has filtered through the conjunctival epithelium from dilated blood vessels + mixed with epithelial debris, mucus and tears
    • a. Watery discharge : serous exudate + reflexly secreted tears. Typical of acute viral and acute allergic conjunctivitis
    • b. Mucoid discharge : typical of vernal conjunctivitis and keratoconjunctivitis sicca
    • c. Purulent discharge : in severe acute bacterial infections
    • d. Mucopurulent discharge : mild bacterial and chlamydial infections.
    • 1. Conjunctival injection
    • 2. Subconjunctival hemorrhage.
    • 3. Oedema
    • 4. Scarring
    • 5. Follicular reaction
    • 6. Papillary reaction
    • Conjunctival Injection : maximal in fornices
    • Velvety beefy-red conj. – bacterial aetiology
    • Subconjunctival Hemorrhages :
    • Usually seen in viral infections also in bacterial (strep.pneumoniae, H. aegypticus)
    • Oedema (chemosis) :
      • Occurs in severely inflammed conj.
      • Exudation of protein rich fluid through the walls of the inflammed blood vessels producing a translucent swelling.
      • Large redundant folds may form in fornices.
      • Severe cases : conj may protrude through the closed eyelids
    • Scarring : seen in Trachoma, ocular cicatricial pemphigoid, atrophic conjunctivitis, prolonged use of topical medications.
  • Conjunctival injection Subconjunctival hemorrhage Conjunctival chemosis Conjunctival scarring
    • Follicular Reaction :
    • Composition : Subepithelial foci of hyperplastic lymphoid tissue within the stroma associated with accessory vascularisation
    • Signs:
      • Multiple discrete, slightly elevated lesions reminiscent of small grains of rice, most prominent in fornices.
      • Each follicle is encircled by a tiny blood vessel and the size of each lesion, which can vary from 0.5 to 5 mm, is related to the severity and duration of the inflammation.
      • As the follicle increases in size, the accompanying vessels are displaced peripherally, eventually appearing as a vascular capsule enclosing the base of the follicle.
    • Causes : viral, chlamydial infections, Parinaud oculoglandular syndrome, Hypersensitivity to topical medications.
  • Conjunctival follicle
    • Papillary Reaction :
    • Non-specific, less diagnostic value than follicular response.
    • Composition :
      • Hyperplastic conjunctival epithelium thrown into numerous folds or projections, with central vessels and a diffuse infiltrate of chronic inflammatory cells, including lymphocytes, plasma cells and eosinophils.
      • Papillae can develop only in the palpebral conjunctival and the bulbar conjunctiva at the limbus, where the conjunctival epithelium is attached to the underlying structures by fibrous septa.
    • Signs :
      • Papillae are most frequently seen in upper palpebral conjunctiva as a fine mosiac – like pattern of elevated polygonal hyperaemic areas separated by paler channels.
      • The central fibrovascular core produces a glomerulus like appearance on reaching the surface.
      • With prolonged inflammation, the fibrous septa which anchor the papillae to the underlying tissues may rupture, leading to confluence and increase in size.
    • Causes : chronic blepharitis, allergic and bacterial conjunctivitis, contact lens wear.
  • Conjunctival papillae
    • 1. Pseudomembranes : coagulated exudate adherent to inflammed conj. epithelium, can be easily peeled off, leaving intact epithelium.
    • Causes : severe adenoviral and gonococcal infection, ligneous conjunctivitis, Steven- Johnson syndrome.
    • 2. True Membranes : infiltrate the superficial layers of the conj. epithelium. Attempts to remove them may be accompanied by tearing of the epithelium and bleeding.
    • Causes : infections from Strep. pyogenes and Diphtheria
  • True membrane Pseudomembrane
    • Lymphatic drainage of the conjunctiva is to preauricular and submandibular nodes, which corresponds to the drainage of the eyelids.
    • Causes : viral, chlamydial and gonococcal infections, Parinaud oculoglandular syndrome.
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    • Indications :
    • 1. Severe purulent conjunctivitis
    • 2. Follicular conjunctivitis
    • 3. Non- specific conjunctival inflammations
    • 4. Neonatal conjunctivitis
    • Specific investigations
    • 1. Cultures
    • 2. Cytological investigation (cellular infiltrates)
    • 3. Inoculation of susceptible cell lines (cytopathic effects)
    • 4. Detection of viral/chlamydial antigens
    • 5. Impression cytology : a piece of cellulose acetate filter paper is pressed against the conj/cornea surface epithelial cells adhere to the paper examined microscopically.
    • Useful in diagnosis of ocular surface neoplasia, dry eyes, ocular cicatricial pemphigoid, limbal stem cell failure and infections.
    • 6. Polymerase chain reaction (PCR) : speedy identification of extremely small quantities of DNA with a very high degree of specificity.
    • Useful for detection of adenovirus, herpes simplex and Chlamydia trachomatis in conjunctival swabs.
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