Acute Conjunctivitis

1. Clinical Overview

Summary

Acute conjunctivitis is an inflammation of the conjunctiva lasting less than four weeks. It is one of the most common ocular complaints in primary care and emergency departments, affecting approximately 1% of all GP consultations. The condition is categorized into infectious (viral and bacterial) and non-infectious (allergic, toxic, or mechanical) aetiologies. [1,2]

Viral conjunctivitis, primarily caused by Adenovirus, accounts for 65–90% of all infectious cases in adults. Bacterial conjunctivitis is less common in adults than in children but remains significant, often caused by Staphylococcus aureus, Streptococcus pneumoniae, or Haemophilus influenzae. Allergic conjunctivitis is a Type I hypersensitivity reaction to environmental allergens (pollen, dust) and is characterized by intense pruritus. [3,4] While most cases are self-limiting, the primary clinical challenge is to differentiate conjunctivitis from sight-threatening "red eye" mimics such as acute glaucoma, uveitis, and microbial keratitis. [5]

Key Facts

• The "Follicle" Sign: Follicles (small, pale, dome-shaped lymphoid aggregates) in the inferior fornix are characteristic of viral or chlamydial conjunctivitis.
• Pre-auricular Lymphadenopathy: A tender pre-auricular node is highly suggestive of viral (adenoviral) infection.
• Wait and See: 65% of bacterial conjunctivitis cases resolve spontaneously within 5 days without antibiotics. [6]
• Contact Lens Warning: A red, painful eye in a contact lens wearer is Microbial Keratitis until proven otherwise. Pseudomonas can perforate the cornea within 24–48 hours.
• The "Morning Glue": Lids that are "stuck together" in the morning is a strong clinical predictor of bacterial aetiology (Sensitivity 77%, Specificity 60%). [7]

Clinical Pearls

The "Itch" Pearl: If it doesn't itch, it's probably not allergic. Pruritus is the most reliable symptom for diagnosing allergic conjunctivitis. If the patient describes "burning" or "grittiness" rather than itching, look for viral/bacterial causes or dry eye.

The "Steroid" Warning: Never prescribe topical steroids (e.g., Maxitrol, Betnesol) for a red eye in primary care. If the redness is due to Herpes Simplex (dendritic ulcer), steroids will trigger a "geographic" ulcer and potential corneal perforation.

The "VA First" Pearl: Always document visual acuity (VA) before examining the eye. A red eye with normal VA is likely conjunctivitis; a red eye with reduced VA is a medical emergency.

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2. Epidemiology & Risk Factors

Incidence & Distribution

• Prevalence: Approximately 6 million people in the United States present with acute conjunctivitis annually. [8]
• Seasonality: Viral conjunctivitis peaks in the winter (associated with URTI); allergic conjunctivitis peaks in the spring and summer (pollen).
• Transmission: Highly contagious via direct contact or fomites. Adenovirus can survive on plastic and metal surfaces for up to 30 days. [9]

Risk Factors

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3. Pathophysiology: The Ocular Defense & The "Red Eye" Cascade

To manage conjunctivitis effectively, one must understand the war being fought on the ocular surface. It is a battle between the highly sophisticated Ocular Surface Defense System (OSDS) and the evasion strategies of pathogens.

1. The Fortress: Ocular Surface Defense Mechanisms

The eye is not a passive mucosa; it is an immune fortress.

• The Tear Film Barrier:
  • Lipid Layer (Meibomian Glands): Prevents evaporation, keeping the surface hydrated.
  • Aqueous Layer (Lacrimal Gland): Contains the biochemical arsenal:
    • Lysozyme: Cleaves the peptidoglycan wall of Gram-positive bacteria.
    • Lactoferrin: Sequesters iron, starving bacteria of essential nutrients.
    • Secretory IgA (sIgA): The "border patrol" antibody that prevents bacterial adhesion to the epithelium.
    • Beta-Defensins: Antimicrobial peptides that punch holes in microbial membranes.
  • Mucin Layer (Goblet Cells): The MUC5AC mucin traps pathogens in a sticky net, which is then blinked away.
• The Mechanical Cleansing:
  • Blinking: The eyelids act as windshield wipers, physically sweeping trapped pathogens into the puncta and down the nasolacrimal duct.
  • Reflex Tearing: Any irritation triggers massive aqueous production to flush the invader.
• Conjunctiva-Associated Lymphoid Tissue (CALT):
  • The conjunctiva contains lymphoid follicles (miniature lymph nodes) housing B and T lymphocytes.
  • Upon antigen detection, Langerhans cells (APCs) integrate the signal and trigger a targeted immune response.

2. The Breach: Why The Eye Gets Red

When the defenses fail, the "Red Eye" response is triggered. This is an inflammatory cascade designed to recruit help.

• Hyperaemia (Redness):
  • Mediators: Histamine, Prostaglandins (PGE2), and Nitric Oxide.
  • Mechanism: Massive relaxation of the vascular smooth muscle in the conjunctival arterioles.
  • Purpose: To increase blood flow, bringing Neutrophils and Complement to the front line.
• Chemosis (Swelling):
  • Mediators: VEGF and Bradykinin.
  • Mechanism: Separation of endothelial cell junctions.
  • Result: Protein-rich plasma leaks into the sub-conjunctival space. This "jelly-like" swelling (chemosis) can lift the conjunctiva off the sclera.
• Exudation (Discharge):
  • Purulent: Dead Neutrophils + Bacteria + Fibrin (Bacterial).
  • Watery: Reflex tearing + Serous transudate (Viral).
  • Mucoid: Mucin overproduction from irritated Goblet cells (Allergic/Dry Eye).

3. Viral Mechanisms: The Adenoviral "Trojan Horse"

Human Adenovirus (HAdV) is the master of ocular infection.

• The Agent: A non-enveloped, double-stranded DNA virus. It is essentially a "naked" capsid, making it resistant to soap, alcohol, and drying.
• The Lifecycle:
  1. Attachment: The viral fiber knob binds to the CAR (Coxsackie-Adenovirus Receptor) on the conjunctival epithelium.
  2. Internalization: The virus is endocytosed.
  3. Lytic Replication: The virus hijacks the cell's machinery to clone itself, then BURSTS the cell open (Lysis).
  4. The "Pseudomembrane": The massive cell death creates a layer of fibrin, necrotic epithelial cells, and leukocytes. This forms a "membrane" on the tarsal plate.
• The "Immune Ghost" (SEI Formation):
  • Weeks after the live virus is gone, viral antigen remains trapped in the corneal stroma.
  • The host immune system attacks this antigen, creating Sub-Epithelial Infiltrates (SEIs).
  • These white, fluffy spots in the cornea cause glare and photophobia.

4. Bacterial Mechanisms: The "Biofilm" War

• Invasion Strategy:
  • Staphylococcus aureus: Produces Exotoxins (Toxic Shock Syndrome Toxin) that cause direct tissue necrosis and blepharitis.
  • Streptococcus pneumoniae: Uses a polysaccharide capsule to hide from phagocytosis.
  • Haemophilus influenzae: Secretes IgA Protease, an enzyme that specifically cuts the IgA antibodies in tears.
  • Pseudomonas aeruginosa: The "Contact Lens Killer".
    • Forms a Biofilm on the contact lens surface (a slime city protected from antibiotics).
    • Secretes Elastase and Alkaline Protease, which digest the corneal collagen.
    • Speed: Can liquefy ("melt") the cornea in under 24 hours.

5. Allergic Mechanisms: The "Itch" Pathway

• Type I Hypersensitivity (Immediate):
  1. Sensitization: Pollen lands on the tear film and penetrates the mucin layer.
  2. Cross-Linking: Allergen binds to two IgE antibodies sitting on a Mast Cell surface.
  3. Explosion (Degranulation): The Mast Cell explodes, releasing 30+ mediators.
     • Histamine: Binds H1 receptors on nerves -> ITCH.
     • Tryptase: Activates PAR-2 receptors -> Inflammation.
• The "Late Phase" (Chronic):
  • Eosinophils arrive 6-12 hours later.
  • They release Major Basic Protein (MBP) and Eosinophil Cationic Protein (ECP).
  • Damage: These proteins are toxic to the corneal epithelium, causing "Shield Ulcers" (Vernal Keratoconjunctivitis).

6. The "Follicle" vs "Papilla" Engine

Differentiating these two findings is the single most important skill in slit-lamp examination.

• Follicles (The "Viral" Sign):

  • What are they?: Hyperplasia of the Lymphoid Tissue (Mini lymph nodes) in the stroma.
  • Structure: A focal aggregation of lymphocytes/plasma cells.
  • Vascular Pattern: Blood vessels run AROUND the base of the bump.
  • Appearance: Pale, Translucent, Dome-shaped. Like "grains of rice" or "tapioca".
  • Found in: Viral conjunctivitis, Chlamydia, Toxic drug reactions (e.g., Brimonidine).

• Papillae (The "Bacterial/Allergic" Sign):

  • What are they?: Hyperplasia of the Epithelium.
  • Structure: Folds of hypertrophic epithelium.
  • Vascular Pattern: A central vascular core (tuft of vessels) runs INTO the center of the bump.
  • Appearance: Red, Velvet-like. If large -> flat-topped "Cobblestones".
  • Found in: Bacterial conjunctivitis, Allergic conjunctivitis, Contact Lens wear (GPC), Floppy Eyelid Syndrome.

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1. Infectious Cascades

• Viral (Adenovirus): The virus binds to receptors on the conjunctival epithelium, leading to cell lysis and an intense lymphoid response (follicle formation). The severe form, Epidemic Keratoconjunctivitis (EKC), involves types 8, 19, and 37 and can cause subepithelial corneal infiltrates—immune complexes that can blur vision for months. [10]
• Bacterial: Pathogens bypass the tear film's antimicrobial defenses (lysozyme, lactoferrin). Neutrophilic recruitment leads to the characteristic purulent discharge.
• Hyperacute (Gonococcal): Neisseria gonorrhoeae can penetrate an intact corneal epithelium, leading to rapid ulceration and perforation.

2. Allergic Mechanism

Allergic conjunctivitis is a classic Type I hypersensitivity reaction. Allergen cross-linking of IgE on mast cells triggers the release of histamine, tryptase, and leukotrienes. This causes immediate vasodilation (redness) and vascular leakage (chemosis). [11]

3. Anatomical Defense

The eye is protected by the Lacrimal Functional Unit. Tears contain IgA and lysozyme. The blink reflex provides mechanical flushing. Disruption of these (e.g., in dry eye or ectropion) increases susceptibility to infection.

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4. Clinical Presentation

Symptoms

• Redness: Usually diffuse; involves both the bulbar and tarsal conjunctiva.
• Discharge:
  • Watery: Viral or Allergic.
  • Purulent (Yellow/Green): Bacterial.
  • Mucoid/Stringy: Allergic.
• Discomfort: Grittiness or "sand in the eye." Severe pain should trigger a search for deeper pathology.
• Vision: Usually normal, though discharge may cause transient blurring that clears with blinking.

Physical Signs

• Follicles: Small, translucent bumps (looks like grains of rice) in the inferior fornix. Sign of viral/chlamydial infection.
• Papillae: Raised red areas with a central vessel (cobblestone appearance). Sign of bacterial/allergic or contact lens-related irritation.
• Chemosis: Swelling of the conjunctiva (looks like a gelatinous blister). Very common in allergic reactions.
• Pre-auricular Node: Tender node just in front of the tragus. Diagnostic for viral (Adenovirus).

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5. Differential Diagnosis: The Dangerous Dozen

The primary role of the clinician is not to diagnose conjunctivitis, but to exclude sight-threatening pathology. The "Red Eye" is a minefield.

1. Acute Angle-Closure Glaucoma (The "Hard" Eye)

• The Killer: Blockage of the trabecular meshwork causes IOP to spike (often > 50mmHg).
• The Patient: Hypermetropic (long-sighted), elderly, Asian/Inuit ethnicity. Onset often in dim light (pupil dilation).
• Symptoms: Severe headache, nausea/vomiting, "Haloes around lights".
• Signs:
  • "Steamy" Cornea: Oedema prevents view of iris details.
  • Mid-Dilated Pupil: Fixed, oval, non-reactive to light.
  • Stony Hard: Palpation reveals a rock-hard globe.
  • Limbality: Redness is greatest at the limbus (Ciliary Flush).
• Action: Emergency. 999/Ambulance. Supine positioning. IV Acetazolamide / Pilocarpine.

2. Anterior Uveitis (Iritis) (The "Aching" Eye)

• The Killer: Inflammation of the iris and ciliary body.
• The Patient: Often young (HLA-B27 positive). History of Ankylosing Spondylitis / IBD.
• Symptoms: Photophobia (Pain on accommodation/light) is the hallmark. Deep ache.
• Signs:
  • Ciliary Flush: Violet ring of redness around the cornea.
  • Pupil: Often small (miotic) and irregular (sinechiae).
  • Slit Lamp: "Cells and Flare" in the anterior chamber (dust in a sunbeam).
  • Hypopyon: Layer of white pus at the bottom of the iris (severe).
• Action: Urgent Referral (24h). Needs Steroids and Cycloplegics.

3. Microbial Keratitis (The "White Spot")

• The Killer: Infection of the corneal stroma.
• The Patient: Contact Lens Wearer (90% risk). Trauma (gardening/organic matter).
• Symptoms: Pain (Foreign body sensation), blurred vision.
• Signs:
  • Ulcer: White opacity on the clear cornea.
  • Fluorescein: Stains the defect vividly.
  • Hypopyon: May be present.
• Action: Emergency. Same-day scrape. Admit for loading dose antibiotics.

4. Scleritis (The "Boring" Pain)

• The Killer: Transmural inflammation of the sclera. Can cause globe perforation (Scleromalacia Perforans).
• The Patient: 50% have systemic autoimmune disease (RA, GPA, Lupus).
• Symptoms: Boring Pain (wakes patient at night). Radiates to jaw/temple.
• Signs:
  • Sectoral Redness: Deep, violaceous (purple) hue.
  • Scleral Thinning: Blueish hue (choroid showing through).
  • Phenylephrine Test: Apply Phenylephrine 2.5%. If redness PERSISTS, it is Scleritis (deep vessels do not blanch). If it blanches, it is Episcleritis.
• Action: Urgent Rheumatology/Ophthalmology. Needs oral NSAIDs/Steroids.

5. Episcleritis (The "Blanching" Red)

• The Mimic: Inflammation of the episclera (layer below conjunctiva). Benign.
• The Patient: Young adults. Stress induced.
• Symptoms: Mild discomfort/tenderness. No severe pain.
• Signs:
  • Sectoral: Usually a wedge of redness.
  • Mobile: Can move the inflamed vessels with a cotton bud (Scleritis vessels don't move).
  • Blanches: Turns white with Phenylephrine.
• Action: Self-limiting. Oral NSAIDs.

6. Herpes Simplex Keratitis (The "Dendrite")

• The Stealth: HSV-1 activation in V1 nerve.
• Symptoms: Pain, watering.
• Signs:
  • Dendritic Ulcer: Branching tree-like lesion with terminal bulbs (stains with Fluorescein).
  • Reduced Sensation: Cornea is numb (check with cotton wisp - carefully).
• Action: Acyclovir ointment ×5/day. NO STEROIDS (Fuels the fire).

7. Herpes Zoster Ophthalmicus (The "Shingles" Eye)

• The Rash: Vesicular rash in V1 dermatome (forehead).
• Hutchinson's Sign: Lesion on the tip of the nose (nasociliary nerve involvement) -> High risk of ocular involvement.
• Signs: Pseudodendrites, Uveitis, High IOP.
• Action: Oral Acyclovir (800mg 5x/day) within 72 hours. Urgent Eye Review.

8. Subconjunctival Haemorrhage (The "Blood Bath")

• The Panic: Burst capillary. Looks terrifying.
• Symptoms: Totally asymptomatic (maybe mild click on blink).
• Signs:
  • Solid Red: Flat, uniform sheet of blood. NO vessels visible.
  • Posterior Border: If you can't see the back edge of the blood, check BP and consider trauma (Base of Skull fracture?).
• Action: Check BP. Reassure. Clears in 2 weeks (goes yellow like a bruise).

9. Orbital Cellulitis (The "Frozen" Eye)

• The Emergency: Infection behind the orbital septum.
• Symptoms: Systemically unwell (Fever). Pain on eye movement.
• Signs:
  • Proptosis: Eye bulges out.
  • Ophthalmoplegia: Eye won't move (frozen muscles).
  • RAPD: Optic nerve compression.
• Action: Emergency. CT Orbit. IV Antibiotics. Surgical decompression?

10. Preseptal Cellulitis (The "Swollen" Lid)

• The Mimic: Infection in front of the septum (lid skin only).
• Signs: Massive lid swelling/erythema. Eye moves normally. Vision normal.
• Action: Oral antibiotics (Augmentin). Safety net for orbital signs.

11. Endophthalmitis (The "Post-Op" Nightmare)

• The Context: Recent eye surgery (Cataract) or Intravitreal Injection (Anti-VEGF) within less than 2 weeks.
• Signs: The eye fills with pus (Hypopyon). Vitritis (loss of red reflex).
• Action: Immediate Tap and Inject (Intravitreal antibiotics). Vision is lost within hours.

12. Carotid-Cavernous Fistula (The "Pulsing" Eye)

• The Vascular: High flow shunt between Carotid and Cavernous Sinus.
• Signs:
  • Corkscrew Vessels: Dilated, tortuous episcleral veins.
  • Bruit: Heard over the globe/temple.
  • Pulsatile Proptosis.
• Action: Neurosurgery referal.

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6. Comprehensive Clinical Atlas: The Systematic Examination

The "Red Eye" is a visual diagnosis. Do not touch the patient until you have observed them.

1. The "Doorway" Inspection

• The Sunglasses Sign: If a patient wears sunglasses in a dark room, they have Severe Photophobia. This implies Iritis or Keratitis, not simple conjunctivitis.
• Lymph Node Alignment: Look at the pre-auricular area. A visible lump is pathognomonic for Parinaud's Oculoglandular Syndrome (Cat Scratch Disease).
• Skin Rash: Look for HZO vesicles on the forehead (V1) or tip of the nose (Hutchinson's Sign).

2. The Systematic Slit-Lamp Examination

If you have access to a slit lamp, use this protocol. If not, use an otoscope or bright torch + loupes.

A. The Eyelids & Lashes (The "Frame")

• Blepharitis: Look for "Collarettes" (scales around the lash base) = Staphylococcal Infection.
• Trichiasis: Are any lashes rubbing against the cornea?
• Molluscum: Look for a pearly, umbilicated nodule on the lid margin. This sheds virus into the eye causing chronic follicular conjunctivitis.
• Meibomian Glands: Press on the lid margin. Does clear oil come out, or "toothpaste"? (MGD).

B. The Conjunctiva (The "Wallpaper")

• Bulbar Conjunctiva:
  • Injection Pattern: Is it diffuse (Conjunctivitis) or Circumcorneal (Ciliary Flush = Iritis)?
  • Chemosis: Is the conjunctiva swollen away from the sclera? (Allergy/Gonorrhoea).
  • Petichiae: Small red dots? (Viral/Strep).
• Tarsal Conjunctiva (Must Evert Lid):
  • Technique: Ask patient to look down. Grasp lashes. Place cotton bud at skin crease. Flip.
  • Search For:
    • Foreign Bodies: Hiding in the subtarsal sulcus.
    • Papillae vs Follicles: (See Pathophysiology).
    • Symblepharon: Bands of scarring connecting lid to globe (Pemphigoid/SJS).
    • Membranes: Peel them. If they bleed -> True Membrane (SJS/Deptheria). If they don't -> Pseudomembrane (Viral).

C. The Cornea (The "Window")

• Marginal Infiltrates: White spots at the corneal edge (Reaction to Staph toxins).
• Punctate Epithelial Erosions (PEE): "Stardust" staining patterns.
• Dendrites: Branching ulcers (HSV).
• Sensation: Test corneal sensation with a wisp of cotton wool (before anaesthetic). Reduced = HSV or V1 Palsy.

3. The Lymph Node Map

• Pre-Auricular Node (PAN): Drain the lateral lids and conjunctiva.
  • Present in: Viral (Adenovirus), Chlamydia, Parinaud's.
  • Absent in: Bacterial (except Gonococcal), Allergic.
• Submandibular Nodes: Drain the medial canthus.

4. Tear Film Assessment

• TBUT (Tear Break Up Time):
  • Instill Fluorescein. Ask patient to blink then stare.
  • Count seconds until black "dry spots" appear in the green dye.
  • less than 10s: Evaporative Dry Eye (MGD).
• Tear Meniscus Height: The pool of tears on the lower lid margin should be > 0.2mm.

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7. Investigations: The Lab

1. The "No Swab" Rule

Routine bacterial swabbing for mild acute conjunctivitis is clinical malpractice in terms of resource stewardship. It costs money, takes 48h, and 65% of cases resolve before the result is back.

2. Indications for Swabbing (The "Must Swab" List)

1. Neonates: Ophthalmia Neonatorum is a blinding emergency. SWAB BOTH EYES.
2. Hyperacute Purulent Discharge: Suspect Gonorrhoea.
3. Chronic Symptoms (> 3-4 weeks): Suspect Chlamydia.
4. Parinaud's Syndrome: Cat Scratch Disease.
5. Post-Operative: Any red eye after recent surgery (Endophthalmitis risk).

3. How to Swab (The Correct Technique)

• Bacterial (MC&S):
  • Use a Charcoal medium swab.
  • Wipe the Inferior Fornix (bottom pocket) from nose to ear.
  • Do NOT touch the lid margin (Staph skin contaminants) or lashes.
• Viral/Chlamydia (PCR/NAAT):
  • Use a dry swab or viral transport medium (VTM).
  • Aggressive Swabbing: You need cells, not just pus. Rub the inferior tarsal plate firmly.
  • Corneal Scrape: (Ophthalmologist Only). Using a needle to scrape corneal cells onto a slide for Gram Stain.

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8. Pediatric & Special Considerations

Children are not just small adults. Their "Red Eye" differential is distinct.

1. Nasolacrimal Duct Obstruction (NLDO)

• Prevalence: 20% of infants born with a "sticky eye".
• History: Tearing and stickiness since birth. Eye is white (no injection) when cleaned.
• Differentiation:
  • Conjunctivitis: Red Eye + Pus.
  • NLDO: White Eye + Pus/Tears.
• Management: Massage the sac. 95% resolve by age 1.

2. Kawasaki Disease

• The Danger: Systemic vasculitis causing coronary artery aneurysms.
• Ocular Sign: Bilateral non-purulent bulbar conjunctivitis (seen in 90% of cases).
• Key: Limbic sparing (white halo around the cornea).
• Action: If "Red Eye + Fever > 5 days", admit to Paediatrics immediately.

3. Stevens-Johnson Syndrome (SJS)

• Trigger: Reaction to drugs (Antibiotics/Anticonvulsants) or infection (Mycoplasma).
• Ocular Sign: Severe purulent conjunctivitis with Membrane formation.
• Risk: Chronic scarring, lid fusion (ankyloblepharon), and blindness.
• Action: Immediate dermatology/ophthalmology admission.

4. Measles

• Prodrome: The "3 Cs"

• Cough, Coryza, Conjunctivitis.

• Sign: Koplik spots (white deposits) on the buccal mucosa.
• Risk: Vitamin A deficiency -> Corneal melting (Keratomalacia).

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9. Differentiation Table (The Master List)

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10. Management: The Acute Algorithm

Management Flowchart (ASCII)

                  [ACUTE RED EYE ASSESSMENT]
                               |
                +--------------v--------------+
                |   RULE OUT RED FLAGS        |
                | (Pain, VA drop, Photophobia)|
                +--------------+--------------+
                               |
                +--------------v--------------+
                |    DIAGNOSE AETIOLOGY       |
                +--------------+--------------+
                /              |               \
       [VIRAL (80%)]      [BACTERIAL]        [ALLERGIC]
          |                    |                     |
  +-------v-------+    +-------v-------+     +-------v-------+
  | SUPPORTIVE    |    | ANTIBIOTICS?  |     | ANTIHISTAMINE |
  | 1. Cool Comp. |    | (See Steward- |     | 1. Olopatadine|
  | 2. Lubes (PF) |    |  ship rules)  |     | 2. Cold Comp. |
  | 3. Peel Memb. |    | Chloram-      |     | 3. Steroids?  |
  | 4. Hygiene    |    | phenicol 0.5% |     | (Specialist)  |
  +---------------+    +-------+-------+     +---------------+
                               |
                       +-------v-------+
                       | REASSESS @ 5d |
                       | (If no change)|
                       +---------------+

1. Viral Conjunctivitis: The "Wait and Weep"

• The Golden Rule: Antibiotics do NOT work. They are toxic to the epithelium and prolong redness (Medicamentosa).
• Supportive Care:
  • Lubricants: Preservative-free (e.g., Hylo-Forte, Thealoz Duo) 4-6 times daily to flush antigen and soothe the ocular surface.
  • Cold Compresses: Vasoconstriction reduces redness/swelling. Use a clean flannel soaked in cold water.
• Betadine Protocol (The "Off-Label" Nuke):
  • Some specialist centers use Povidone-Iodine 5% (1 drop) in the office to kill free viral load. Extremely stinging; requires anaesthetic first. Reserved for severe epidemic control.
• Steroids:
  • Controversial: Only used for SEIs that cause significant Drop in VA (e.g., less than 6/12) or severe membrane formation.
  • Risk: Prolongs viral shedding. NEVER start without Ophthalmology review to rule out HSV.

2. Bacterial Conjunctivitis: Antibiotic Stewardship

• Mild Cases: Self-limiting (5-7 days). Bathing lids with cooled boiled water is sufficient.
• Moderate/Severe:
  • Chloramphenicol 0.5%: Broad spectrum (Gram pos/neg). Excellent penetration (Lipophilic).
    • Dose: Q2H for 2 days -> QDS for 5 days.
    • Safety: Aplastic Anaemia risk is theoretically possible but negligible in topical use (1 in 10 million).
  • Fusidic Acid 1% (Fucithalmic):
    • Target: Gram Positive (Staph aureus).
    • Advantage: Viscous gel (BD dosing). Better compliance in kids.
  • Fluoroquinolones (Ofloxacin/Moxifloxacin):
    • Restricted: Save for Contact Lens wearers (Pseudomonas) or severe ulcers.
    • Resistance: Overuse leads to resistant Keratitis.

3. Allergic Conjunctivitis: The "Dual Action" Era

• First Line: Olopatadine (Opatanol) or Ketotifen.
  • Mechanism: H1 Antagonist (Immediate relief) + Mast Cell Stabilizer (Long term prevention).
  • Dosing: BD (Twice daily). Effect lasts 12 hours.
• Second Line: Sodium Cromoglicate (Cromolyn).
  • Pro: Safe, cheap.
  • Con: Takes 2 weeks to "load" mast cells. QDS dosing. Good for prophylaxis (start before pollen season), bad for acute treatment.
• Oral Antihistamines: Loratadine/Cetirizine.
  • Role: Helpful for associated rhinitis/sneezing. Less effective for ocular itch than topical drops.

4. Advanced Protocol: Membrane Peeling

• Indication: Presence of a pseudomembrane (fibrinous exudate) on the tarsal plate in severe Adenoviral infection.
• Why: It acts like sandpaper, scarifying the cornea with every blink.
• Action:
  1. Topical Anaesthetic (Proxymetacaine).
  2. Use a cotton bud or forceps.
  3. Firmly wipe/peel the white membrane off the tarsal plate.
• Result: It WILL bleed (this is diagnostic of a true interface). The patient will feel immediate relief from the "foreign body" sensation.

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11. Pharmacology: The Drug Arsenal

Understanding the molecular mechanism prevents indiscriminate prescribing.

1. Antibiotics

2. The preservative Paradox: BAK Toxicity

• The Agnet: Benzalkonium Chloride (BAK) is the most common preservative in eye drops.
• The Problem: It is a detergent. It disrupts bacterial cell walls... BUT it also disrupts human corneal epithelial cells.
• The Sign: Punctate Epithelial Erosions (PEE). The cornea looks like a sky full of stars under fluorescein.
• The Cycle: Patient has red eye -> Uses BAK drops -> Gets toxic keratitis -> Eye gets redder -> Uses MORE drops.
• Solution: Switch to Preservative-Free (Minims or COMOD systems) if using drops > 4x/day or for long durations.

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12. Special Protocols: High-Stakes Patients

1. The Contact Lens Wearer (The "CLARE" Protocol)

Rule: A red eye in a contact lens wearer is Microbial Keratitis until proven otherwise.

• Pathophysiology: Local hypoxia + Micro-abrasions + Bacterial Biofilm (Pseudomonas aeruginosa).
• CLARE (Contact Lens Acute Red Eye): An inflammatory non-ulcerative reaction to endotoxins from Gram-negative bacteria colonizing the lens.
• Management:
  1. STOP LENS WEAR IMMEDIATELY.
  2. Stain with Fluorescein:
     • Epithelial Defect / Infiltrate: URGENT REFERRAL to Ophthalmology (Same day). Needs corneal scrape.
     • No Defect: Treat as bacterial conjunctivitis but Use Fluoroquinolone (Ofloxacin/Ciprofloxacin) to cover Pseudomonas. Chloramphenicol is INSUFFICIENT.
     • Do NOT patch (promotes bacterial incubator conditions).
  3. Prognosis: Pseudomonas can perforate the cornea in 24 hours ("Melting Cornea").
  4. The Lenses: Discard the current lenses and case. Do not restart wear until white + 24 hours.

2. Ophthalmia Neonatorum (The Neonatal Emergency)

Conjunctivitis in the first 28 days of life. Blinding if missed.

• Chemical (less than 24 hours): Reaction to prophylaxis (Silver nitrate/Erythromycin). Self-limiting.
• Gonococcal (Day 2–5):
  • Sign: Hyperacute, purulent, lids stick shut, chemosis.
  • Risk: Rapid corneal perforation / Sepsis / Meningitis.
  • Action: Medical Emergency. Admission + IV Ceftriaxone + Saline Irrigation.
• Chlamydial (Day 5–14):
  • Sign: Watery -> Mucopurulent. Bloody discharge (friable conjunctiva).
  • Systemic: Associated with Pneumonitis (monitor breathing).
  • Action: Systemic Erythromycin (Topical is ineffective).
• Herpes Simplex (Day 14+): Vesicles. Risk of systemic dissemination (Encephalitis). Needs IV Aciclovir.

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9. Clinical Case Scenarios

Case 1: The "Morning Glue" (Bacterial)

• Patient: 32M, "stickiest eyes of my life", glued shut this morning. No pain, no visual loss.
• Exam: Bilateral injection, purulent discharge in fornices. Cornea clear.
• Management:
  • Decision: This is likely bacterial. However, 65% resolve alone.
  • The "Delayed Script": Issued a prescription for Chloramphenicol but advised: "Bathe eyes for 48 hours. Only use drops if it's not improving."
  • Outcome: Resolved spontaneously by Day 4. Antibiotics saved.

Case 2: The "Office Outbreak" (Viral/EKC)

• Patient: 45F, teacher. Starts in right eye, moves to left eye 3 days later. Watery, "gritty", tender pre-auricular node.
• Exam: Follicles in inferior fornix. Pinpoint subconjunctival haemorrhages.
• Diagnosis: Epidemic Keratoconjunctivitis (EKC) - Adenovirus Serotype 8.
• Management:
  • Strict hygiene advice (2 weeks off work - highly contagious).
  • Preservative-free lubricants.
  • Follow-up (Week 3): Patient complains of "glare". Exam shows Subepithelial Infiltrates (SEIs). Referred for weak topical steroid (FML) taper.

Case 3: The "Contact Lens Masquerade" (Microbial Keratitis)

• Patient: 22F, sleeps in soft lenses. Woke up with severe pain (8/10) and sensitive to light.
• Exam:
  • VA: 6/18 (Reduced).
  • Slit Lamp: 1mm white spot at 4 o'clock on cornea.
  • Fluorescein: Stains vividly over the spot.
• Action: This is an Ulcer. Immediate referral. Corneal scrape performed -> Pseudomonas confirmed. Admitted for hourly Ofloxacin drops ("Loading dose"). Sight saved, small scar remains.

Case 4: The "Deep Bore" (Scleritis)

• Patient: 60F with Rheumatoid Arthritis. "Red eye" for 1 week. Complains of "boring pain" that wakes her at night.
• Exam:
  • Sectoral redness (violaceous hue).
  • Phenylephrine Test: Drops applied -> Vessels did NOT blanch (indicates deep vascular involvement).
• Diagnosis: Scleritis (Not conjunctivitis).
• Management: Systemic immunosuppression (Oral NSAIDs / Steroids). Urgent Rheumatology review.

Case 5: The "Silent Spreader" (Chlamydia)

• Patient: 24M. Red eye for 6 weeks. Treated with Chloramphenicol x2 (failed).
• Exam:
  • Large "cobblestone" follicles in the inferior fornix.
  • Mild pannus (vessels growing onto cornea).
• History: New sexual partner 2 months ago.
• Diagnosis: Adult Inclusion Conjunctivitis.
• Action: Swab for Chlamydia PCR. Referred to GUM clinic. Treated with Oral Doxycycline 100mg BD for 10 days (Topical therapy is useless).
• Key Learning: Chronic unilateral red eye in a young adult is Chlamydia until proven otherwise.

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14. The Discharge Bible

Patients Frequently Ask...

"Am I contagious?"

• Viral: YES. Extremely. You are a bio-hazard for 10-14 days. Adenovirus can survive on a doorknob for a week.
• Rule: If the eye is weeping, you are shedding virus.
• Bacterial: Yes, but contagion drops significantly after 24 hours of treatment.

"Can I wear my contact lenses?"

• Absolutely Not. You must stop wearing lenses immediately.
• The 24-hour Rule: Wait until the eye has been completely white and symptom-free for at least 24 hours after finishing your drops (usually 7 days total off lenses).
• Equipment: Throw away the current pair and the case. Start fresh.

"How do I put the drops in?" (The 6-Step Technique)

1. Wash hands thoroughly.
2. Tilt head back (look at the ceiling).
3. The Pocket: Pull the lower lid down with your index finger.
4. The Drop: Squeeze one drop into the pocket (NOT onto the sensitive cornea).
5. Punctal Occlusion: Close your eye and press the inner corner (tear duct) for 1 minute. This stops the drop draining into your nose/throat and keeps it in the eye.
6. Hygiene: Do not let the bottle tip touch your eye or lashes.

"My vision is blurry after the ointment!"

• This is normal. Ointments (like Chloramphenicol 1%) are greasy. We recommend using them at night for this reason.

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15. International Guidelines Comparison

*ECCO: European Consensus guidelines.

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16. Complications

Most conjunctivitis is benign, but complications can be sight-threatening.

1. Corneal Ulceration: Especially with Pseudomonas (CL wearers) or Gonococcus. Can lead to perforation and loss of the eye.
2. Subepithelial Infiltrates (SEIs): Post-adenoviral immune haze. Causes glare and reduced contrast sensitivity for months.
3. Symblepharon: Adhesion of the eyelid to the globe. Seen in cicatrizing conjunctivitis (SJS, Pemphigoid, Chemical Burns).
4. Super-infection: Using steroids on a fungal or herpetic eye leads to catastrophic spread.

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17. Evidence & Landmark Trials

Evidence-based medicine in ophthalmology challenges the "antibiotic reflex".

1. The Rose Trial (Lancet 2005)

• Study Question: Do topical antibiotics improve recovery in children with acute infective conjunctivitis?
• Method: RCT, N=326. Chloramphenicol vs Placebo.
• Results: Cure rates at Day 7 were 86% (Antibiotic) vs 83% (Placebo). Non-significant.
• Impact: Supports "Wait and See" policy.

2. The Jefferis Meta-Analysis (BJGP 2011)

• Finding: Purulent discharge is a predictor of bacterial cause, but NOT a predictor of non-resolution. Even "pus-filled" eyes resolve spontaneously in 60% of cases.

3. The SCUT Trial (Arch Ophthalmol 2010)

• While primarily about Ulcers, the Steroids for Corneal Ulcers Trial showed that adding steroids to antibiotics did not improve visual acuity but did not cause harm if the antibiotic was effective.
• Relevance: Highlights that steroids are not a magic bullet even in severe disease.

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18. Single Best Answer (SBA) Questions

Question 1

A 24-year-old male presents with a red, watery eye for 2 days. He has a sore throat and a tender pre-auricular lymph node. Visual acuity is 6/6. What is the most likely causative agent?

• A) Staphylococcus aureus
• B) Adenovirus
• C) Chlamydia trachomatis
• D) Herpes Simplex Virus
• E) Grass Pollen
• Answer: B. The combination of watery discharge, sore throat, and a pre-auricular node is classic for adenoviral conjunctivitis (Pharyngoconjunctival Fever).

Question 2

A patient with bilateral red, itchy eyes and stringy mucoid discharge is diagnosed with allergic conjunctivitis. Which is the most effective first-line topical treatment?

• A) Sodium Cromoglicate
• B) Chloramphenicol
• C) Olopatadine
• D) Dexamethasone
• E) Artificial Tears
• Answer: C. Olopatadine (Dual-action) provides rapid relief, unlike mast cell stabilizers which take weeks to load.

Question 3

A 28-year-old contact lens wearer presents with pain (8/10) and a white corneal spot. Next step?

• A) Chloramphenicol drops
• B) Stop lenses, review in 48h
• C) Urgent Ophthalmology Referral
• D) Fluorescein stain and discharge
• E) Olopatadine
• Answer: C. Pain + Opacity in a CL wearer = Microbial Keratitis until proven otherwise. Needs scraping and intense Fluoroquinolones.

Question 4

What is the recommended duration for Chloramphenicol in bacterial conjunctivitis?

• A) 2 days
• B) 5 days
• C) 10 days
• D) 14 days
• E) Until white
• Answer: B. A 5-day course (or 48h after resolution) is standard.

Question 5

Which finding best differentiates viral from bacterial conjunctivitis?

• A) Chemosis
• B) Hyperaemia
• C) Follicles
• D) Papillae
• E) Crusting
• Answer: C. Follicles (pale lymphoid aggregates) are the hallmark of viral infection.

Question 6 (The "Red Flag")

A 45-year-old female presents with a red eye, non-reactive mid-dilated pupil, and severe brow ache. She sees halos around lights. Diagnosis?

• A) Viral Conjunctivitis
• B) Anterior Uveitis
• C) Acute Angle Closure Glaucoma
• D) Scleritis
• E) Abrasion
• Answer: C. This is not conjunctivitis. It is an ocular emergency requiring immediate IOP lowering.

Question 7

Which organism is the most common cause of Hyperacute Purulent Conjunctivitis in neonates?

• A) Adenovirus
• B) Staph aureus
• C) Neisseria gonorrhoeae
• D) Chlamydia trachomatis
• E) Pseudomonas
• Answer: C. Gonococcus causes rapid, severe purulence and can perforate the cornea.

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19. Global Health Context: Trachoma

While conjunctivitis is a minor inconvenience in the West, it is a leading cause of blindness globally.

1. The Disease

• Agent: Chlamydia trachomatis (Serotypes A, B, Ba, C).
• Vector: Flies (Musca sorbens) and fomites.
• Pathology: Recurrent infection in childhood -> Tarsal scarring -> Trichiasis (in-turned lashes) -> Corneal Opacity.

2. The SAFE Strategy (WHO 2030 Goal)

• Surgery (for Trichiasis).
• Antibiotics (Mass Azithromycin).
• Facial Cleanliness.
• Environmental Improvement.

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20. References

1. Azari AA, Barney NP. Conjunctivitis: a systematic review of diagnosis and treatment. JAMA. 2013;310(16):1721-9.
2. Cronau H, et al. Diagnosis and management of red eye in primary care. Am Fam Physician. 2010;81(2):137-44.
3. AAO. Conjunctivitis Preferred Practice Pattern. American Academy of Ophthalmology. 2018.
4. Rose PW, et al. Chloramphenicol treatment for acute infective conjunctivitis in children in primary care: a randomised double-blind controlled trial. Lancet. 2005;366(9479):37-43.
5. Jefferis J, et al. Acute infective conjunctivitis in primary care: who needs antibiotics? An individual patient data meta-analysis. Br J Gen Pract. 2011;61(590):e542-8.
6. Sheikh A, Hurwitz B. Antibiotics versus placebo for acute bacterial conjunctivitis. Cochrane Database Syst Rev. 2012;(9):CD001211.
7. Dart JK, et al. Contact lens-associated microbial keratitis: causative organisms and management. Eye. 2012.
8. World Health Organization. Trachoma Control: A Guide for Programme Managers. WHO. 2006.

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Last Updated: 2026-01-05 | MedVellum Editorial Team | Status: Target (> 1500 Lines)