Conjunctival diseases: Conjunctivitis. Etiology. Classification. Diagnostics. Treatment. Dystrophic diseases of the conjunctiva.

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Conjunctival Diseases: Conjunctivitis and Dystrophic Conditions

Based primarily on Kanski's Clinical Ophthalmology: A Systematic Approach, 10th Edition

ANATOMY OF THE CONJUNCTIVA

The conjunctiva is a transparent mucous membrane lining the inner surface of the eyelids and the anterior surface of the globe, terminating at the corneoscleral limbus. It is divided into:

Palpebral conjunctiva — firmly attached to the posterior tarsal plates
Fornical conjunctiva — loose and redundant
Bulbar conjunctiva — covers the anterior sclera; continuous with corneal epithelium at the limbus

Histology: Non-keratinizing stratified squamous epithelium (~5 cells deep) with mucus-secreting goblet cells (densest inferonasally and in the fornices). The stroma contains accessory lacrimal glands of Krause and Wolfring. Conjunctiva-associated lymphoid tissue (CALT) mediates ocular surface immunity.

CONJUNCTIVITIS

Clinical Features of Conjunctival Inflammation

Symptoms (non-specific): lacrimation, grittiness, stinging, burning. Itching is the hallmark of allergic disease. Significant pain, photophobia, or foreign body sensation suggests corneal involvement.

Discharge character is diagnostically important:

Discharge Type	Typical Cause
Watery/serous	Acute viral or acute allergic
Mucoid	Chronic allergic conjunctivitis, dry eye
Mucopurulent	Chlamydial or acute bacterial
Moderately purulent	Acute bacterial
Severe/hyperacute purulent	Gonococcal infection

Conjunctival reaction types:

Hyperaemia — diffuse, beefy-red, more intense away from the limbus; suggests infectious/toxic etiology
Follicles — small, avascular, elevated lesions with a pale center surrounded by vessels; seen in viral, chlamydial, and toxic conjunctivitis
Papillae — vascularized elevations with a central fibrovascular core; seen in bacterial and allergic conjunctivitis
Chemosis — conjunctival oedema
Membrane/pseudomembrane — fibrinous exudate on the tarsal surface; seen in severe bacterial (GAS), adenoviral EKC, and toxic reactions

CLASSIFICATION AND ETIOLOGY

1. Bacterial Conjunctivitis

Acute Bacterial Conjunctivitis

Etiology: Most common isolates:

Streptococcus pneumoniae
Staphylococcus aureus
Haemophilus influenzae
Moraxella catarrhalis
Neisseria gonorrhoeae (severe/hyperacute — can penetrate intact corneal epithelium)
Neisseria meningitidis (rare, mainly children)

Clinical features:

Acute onset of redness, grittiness, burning, discharge
Usually bilateral (second eye involved 1–2 days later)
Eyelids stuck together on waking
Discharge: initially watery → rapidly mucopurulent
Hyperacute purulent discharge → suspect gonococcal/meningococcal
Superficial punctate epithelial erosions
Peripheral corneal ulceration possible with gonococcal/meningococcal infection

Investigations (not routine; indicated in severe cases):

Conjunctival swabs + scrapings for Gram stain (Gram-negative intracellular diplococci → gonococcus)
Culture on chocolate agar or Thayer-Martin medium for N. gonorrhoeae
PCR for cases failing treatment (to rule out chlamydial/viral)

Treatment:

Most cases are self-limiting (~60% resolve in 1–2 weeks without treatment)
Topical broad-spectrum antibiotics (chloramphenicol, fusidic acid, quinolones) reduce duration
Gonococcal conjunctivitis: topical antibiotic + systemic ceftriaxone (third-generation cephalosporin); saline irrigation; co-treat for Chlamydia
Good hygiene; do not share towels; hand washing

Adult Chlamydial (Inclusion) Conjunctivitis

Etiology: Chlamydia trachomatis serovars D–K. Affects 5–20% of sexually active young adults; spread by autoinoculation from genital secretions (~90%) or eye-to-eye contact (~10%). Incubation ~1 week.

Clinical features:

Subacute onset of unilateral or bilateral redness, watering, discharge
Tender preauricular lymphadenopathy
Large follicles prominent in the inferior fornix
Superficial punctate keratitis; perilimbal subepithelial corneal infiltrates (after 2–3 weeks)
Mild conjunctival scarring and superior corneal pannus in chronic cases
Genital symptoms (urethritis, discharge) often present

Investigations:

Tarsal conjunctival scrapings: Giemsa stain (basophilic intracytoplasmic inclusion bodies)
PCR/NAAT (nucleic acid amplification test) — most sensitive
Direct immunofluorescence (~90% sensitivity), enzyme immunoassay

Treatment:

Systemic treatment is essential to eradicate the genital reservoir
Azithromycin 1 g single dose (first choice)
Doxycycline 100 mg twice daily × 7–14 days (alternative)
Erythromycin 500 mg four times daily × 14 days (if tetracycline contraindicated — e.g., pregnancy)
Sexual contacts must be traced and treated
Topical antibiotics are inadequate alone

Trachoma

Etiology: C. trachomatis serovars A, B, Ba, C. Leading infectious cause of preventable blindness worldwide (endemic in sub-Saharan Africa, Middle East, South Asia).

WHO SAFE strategy: Surgery (for trichiasis), Antibiotics (azithromycin 20 mg/kg single dose, or doxycycline), Facial cleanliness, Environmental improvement.

Neonatal Conjunctivitis (Ophthalmia Neonatorum)

Conjunctival inflammation within the first month of life; most common infection in neonates (up to 10%).

Causes and timing:

Cause	Onset
Chemical (prophylaxis irritation)	First few days
N. gonorrhoeae	First week
Staphylococci, other bacteria	End of first week
Herpes simplex virus (HSV-2)	1–2 weeks
Chlamydia trachomatis	1–3 weeks

Treatment: Gonococcal → parenteral ceftriaxone + topical antibiotic; Chlamydial → oral erythromycin × 2 weeks; HSV → systemic aciclovir (high-dose IV in neonates).

2. Viral Conjunctivitis

Etiology: Adenovirus causes ~90% of viral conjunctivitis. Highly contagious; survives on dry surfaces for weeks; spread by contact with ocular/respiratory secretions. Other agents: enterovirus, coxsackievirus, HSV, varicella-zoster, molluscum contagiosum.

Clinical variants:

Form	Serovars	Key Features
Non-specific acute follicular conjunctivitis	Multiple adenovirus serovars	Most common; mild; bilateral; upper respiratory symptoms
Pharyngoconjunctival fever (PCF)	Ad 3, 4, 7	Prominent sore throat; keratitis in ~30%
Epidemic keratoconjunctivitis (EKC)	Ad 8, 19, 37	Most severe; keratitis in ~80%; photophobia marked; subepithelial infiltrates; pseudomembranes
Acute haemorrhagic conjunctivitis	Enterovirus 70, Coxsackievirus A24	Tropical; rapid onset; marked conjunctival haemorrhage; resolves 1–2 weeks
HSV conjunctivitis	HSV-1/2	Unilateral; follicular; associated skin vesicles
Molluscum-associated	Poxvirus	Chronic follicular; look for lid margin molluscum lesions

Diagnosis: Clinical. PCR for specific viruses if needed. Pseudomembranes and subepithelial infiltrates distinguish EKC.

Treatment:

Mostly supportive (lubricants, cold compresses, antihistamines for discomfort)
Topical povidone-iodine (0.5–1%) has shown benefit in reducing viral load and duration
Short courses of topical steroids for significant subepithelial infiltrates reducing vision in EKC (but may prolong viral shedding)
Topical aciclovir for HSV conjunctivitis
Hygiene measures are critical to prevent spread (avoid touching eyes, no shared towels, handwashing)

3. Allergic Conjunctivitis

Pathophysiology: Type I (IgE-mediated) hypersensitivity with mast cell degranulation; eosinophil recruitment. Itching is the cardinal symptom.

Forms:

a) Seasonal/Perennial Allergic Conjunctivitis (SAC/PAC)

SAC: triggered by seasonal allergens (pollen, grass)
PAC: perennial allergens (house dust mite, animal dander)
Bilateral itching, watering, mild papillary reaction, chemosis
Treatment: topical antihistamines (olopatadine, ketotifen), mast cell stabilizers (sodium cromoglicate, nedocromil), combination agents; allergen avoidance

b) Vernal Keratoconjunctivitis (VKC)

Young males in hot climates; seasonal exacerbations
Superior giant papillae ("cobblestoning") on upper tarsal conjunctiva; limbal papillae with Horner-Trantas dots (eosinophil aggregates)
Mucoid "ropy" discharge
Shield ulcer on upper cornea (complication)
Treatment: mast cell stabilizers, topical steroids (short courses), topical cyclosporin 1–2%, supratarsal steroid injection; cold compresses

c) Atopic Keratoconjunctivitis (AKC)

Adults with atopic dermatitis
Preferential inferior palpebral involvement (vs. superior in VKC)
Cicatricial changes, symblepharon, forniceal shortening possible
Horner-Trantas dots can also appear
Treatment: similar to VKC; systemic immunosuppression may be needed for severe cases

d) Giant (Mechanical) Papillary Conjunctivitis

Associated with contact lens wear, ocular prostheses, exposed sutures
Giant papillae on upper tarsal conjunctiva
Treatment: remove/replace offending object; lubricants; mast cell stabilizers

e) Contact Allergic Blepharoconjunctivitis

Type IV (delayed) hypersensitivity to topical medications, preservatives, cosmetics
Lid erythema + inferior conjunctival follicles/papillae
Treatment: identify and eliminate allergen; short-course topical steroid

DIAGNOSTICS — GENERAL APPROACH

Investigation	Indication
Gram stain of scrapings	Suspected gonococcal/meningococcal; neonatal conjunctivitis
Giemsa stain	Suspected chlamydial (intracytoplasmic inclusions)
PCR/NAAT	Chlamydial, HSV, adenoviral confirmation
Culture (chocolate agar/Thayer-Martin)	N. gonorrhoeae
Direct immunofluorescence	Chlamydia (~90% sensitivity)
Conjunctival scraping cytology	Eosinophils → allergic; mononuclear cells → viral; PMNs → bacterial
Thyroid function	Superior limbic keratoconjunctivitis
Biopsy/impression cytology	Keratinization, neoplasia, pemphigoid

DYSTROPHIC (DEGENERATIVE) DISEASES OF THE CONJUNCTIVA

1. Pinguecula

Definition: A yellowish-white, slightly elevated, triangular deposit in the interpalpebral bulbar conjunctiva adjacent to the limbus (nasally more than temporally). It does not extend onto the cornea.

Pathogenesis: Actinic (UV) damage and chronic dryness cause elastotic degeneration of subepithelial stromal collagen with accumulation of abnormal, curled elastic-like fibres (elastotic material). Associated with chronic UV exposure (outdoor workers, equatorial regions), dry/dusty environments, and aging.

Histology: Elastotic (basophilic) degeneration of collagen fibres in the substantia propria; overlying epithelium may be thinned.

Clinical features:

Usually asymptomatic; cosmetically noticeable
Pingueculitis — acute inflammation of the lesion (redness, irritation) due to surface dryness or UV exposure
Rarely progresses to pterygium

Treatment:

Observation in most cases
Lubricants ± short course topical steroid for pingueculitis
Excision for cosmetic reasons or significant irritation (low recurrence rate)
Thermal laser ablation

2. Pterygium

Definition: A triangular fibrovascular subepithelial ingrowth of degenerative bulbar conjunctival tissue that crosses the limbus and encroaches onto the cornea, invading Bowman's layer. Typically develops nasally.

Pathogenesis: Same UV-related elastotic degeneration as pinguecula, but with angiogenic activation enabling corneal invasion. Familial tendency. Histologically similar to pinguecula.

Pseudopterygium differs: adhesion of conjunctival band to compromised cornea following chemical burns, corneal ulcers, or cicatrizing conjunctivitis — not a true degeneration.

Clinical features:

Symptoms: Most small lesions are asymptomatic. Irritation and grittiness from "dellen" effect (localized tear film disruption at the advancing edge). Vision affected when the visual axis is obscured or astigmatism induced.
Signs: Triangular, vascularized, wing-shaped lesion with:
- Cap — grey zone of Bowman layer dissolution ahead of the advancing head
- Head — elevated leading edge on the cornea
- Body — vascular tissue on the sclera
- Stocker line (iron deposition at the advancing edge of the head)

Treatment:

Conservative: lubricants, UV protection (sunglasses), topical steroids for inflammation
Surgical excision indicated for:
- Encroachment toward visual axis
- Induced astigmatism
- Persistent symptoms
- Cosmesis
Recurrence is a major problem after simple excision (~30–80%)
Anti-recurrence strategies:
- Conjunctival autograft (preferred, recurrence ~5–10%)
- Amniotic membrane transplantation
- Adjunctive mitomycin C (topical or subconjunctival)
- Beta-irradiation (now less used)

3. Conjunctival Concretions

Small, yellowish deposits of inspissated secretions in the fornices or palpebral conjunctiva; common in elderly; generally asymptomatic unless superficial (may cause foreign body sensation); treated by simple evacuation with a needle if symptomatic.

4. Conjunctivochalasis

Redundant, loose bulbar conjunctival tissue (between the globe and lower lid) causing epiphora, foreign body sensation, and dry eye symptoms. Treatment: lubricants; surgical resection in refractory cases.

5. Retention (Epithelial Inclusion) Cysts

Translucent, thin-walled cysts arising from buried conjunctival epithelium after surgery or trauma. Asymptomatic unless large; treated by excision or needle aspiration.

Summary Comparison: Pinguecula vs. Pterygium

Feature	Pinguecula	Pterygium
Location	Bulbar conjunctiva, near limbus	Crosses limbus onto cornea
Corneal involvement	No	Yes (invades Bowman layer)
Appearance	Yellowish elevated deposit	Triangular fibrovascular ingrowth
Vision affected	No	Yes (astigmatism, axis obscuring)
Histology	Elastotic collagen degeneration	Same + angiogenesis
Recurrence after excision	Low	High (up to 80% simple excision)
Primary treatment	Observation/lubricants	Surgical excision + conjunctival autograft

— Kanski's Clinical Ophthalmology: A Systematic Approach, 10th Edition (Elsevier, 2023)

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