Bacterial Conjunctivitis, Keratitis and Uveitis

Organizing Principle — Anatomy = Severity Gradient

Conjunctiva (self-limited, vision-sparing) < Cornea/keratitis (OPHTHALMIC EMERGENCY, vision-critical, vulnerable) < Uvea/uveitis (sight-threatening intraocular inflammation, often non-infectious).

Bacterial Conjunctivitis

Organisms: S. aureus, S. pneumoniae, H. influenzae (community-acquired). Conjunctival injection + PURULENT/mucopurulent discharge, often bilateral (starts unilateral). KEY DISTINCTION vs viral (Viral Keratoconjunctivitis topic): PURULENT (bacterial) vs WATERY (viral) discharge — drives Tx decision (topical Abx vs supportive).

Ophthalmia neonatorum (birth canal acquisition):

• N. gonorrhoeae: SEVERE, hyperacute purulent conjunctivitis, presents first few DAYS of life — sight-threatening
• C. trachomatis: MILDER, more indolent, presents LATER (5-14 days) Testable timing/severity distinction. Historic prevention: prophylactic neonatal eye care (erythromycin/silver nitrate).

Bacterial Keratitis (EMERGENCY)

Organisms: Pseudomonas aeruginosa, S. aureus. KEY RISK FACTOR: CONTACT LENS WEAR (contaminated lens/case biofilm + corneal microtrauma = entry portal through protective epithelium) — high-yield association. Pseudomonas keratitis can progress to corneal perforation rapidly if not aggressively treated. Presentation: pain, photophobia, ↓vision, corneal infiltrate/ulcer ± HYPOPYON (layered inflammatory cell/pus collection, anterior chamber, horizontal fluid level) = sign of significant intraocular involvement.

Bacterial Uveitis

Overall MORE OFTEN non-infectious/autoimmune (contrast vs conjunctivitis/keratitis = predominantly infectious). Infectious causes: uncommon direct bacterial; more commonly uveitis as SYSTEMIC infection manifestation — TB, syphilis, leptospirosis (connects to those topics). Presentation: pain, photophobia, blurred vision + slit-lamp finding: ANTERIOR CHAMBER CELLS AND FLARE (active intraocular inflammation marker).

Diagnosis/Treatment

Conjunctival/corneal scraping → Gram stain + culture (esp. important for keratitis — emergency, need organism-directed Tx). Topical antibiotics = backbone. Keratitis often needs FORTIFIED (compounded, higher-concentration) topical Abx for adequate corneal penetration — contrast vs standard-concentration sufficient for conjunctivitis alone. Uveitis: treat underlying systemic infectious cause if present + topical/systemic corticosteroids for inflammatory component.

Three Anatomically Distinct Compartments, Three Distinct Severity Levels

The eye’s three main infectable compartments — the conjunctiva (the thin mucous membrane covering the sclera and inner eyelids), the cornea (the eye’s clear, avascular anterior refractive surface), and the uveal tract (the iris, ciliary body, and choroid, collectively the eye’s middle, vascular layer) — carry substantially different clinical severity and visual-prognosis implications: conjunctivitis is generally self-limited and vision-sparing; keratitis is a genuine ophthalmic emergency given the cornea’s role in vision and its comparative vulnerability; and uveitis, while less commonly directly infectious than conjunctivitis, carries substantial sight-threatening potential from intraocular inflammation.

Bacterial Conjunctivitis

Bacterial conjunctivitis is caused by a range of organisms, classically Staphylococcus aureus, Streptococcus pneumoniae, and Haemophilus influenzae in general community-acquired cases, presenting with conjunctival injection (redness), purulent/mucopurulent discharge, and typically bilateral involvement (often starting unilaterally before spreading) — genuinely, specifically important to distinguish clinically from viral conjunctivitis (see Viral Keratoconjunctivitis) primarily by the purulent, rather than watery, discharge character, since this distinction has direct practical treatment implications (topical antibiotics for bacterial; supportive care for viral). Ophthalmia neonatorum — neonatal conjunctivitis acquired during passage through an infected birth canal — deserves specific mention here for its genuinely important, age-specific aetiological profile: Neisseria gonorrhoeae classically causes a severe, rapidly progressive, potentially sight-threatening hyperacute purulent conjunctivitis presenting within the first few days of life (see Gonococcal Urethritis for the organism’s general biology), while Chlamydia trachomatis causes a comparatively milder, more indolent conjunctivitis typically presenting somewhat later (5-14 days) — a genuinely important, specifically testable timing/severity distinction between the two classic causes of ophthalmia neonatorum, historically addressed by routine prophylactic neonatal eye care (erythromycin or silver nitrate instillation shortly after birth).

Bacterial Keratitis

Bacterial keratitis (corneal infection) represents a genuine ophthalmic emergency given the cornea’s essential, irreplaceable role in vision and its comparative structural vulnerability to scarring — Pseudomonas aeruginosa and Staphylococcus aureus are classic causative organisms, with contact lens wear being a genuinely important, specifically testable major risk factor (contaminated lens/lens-case biofilm, and corneal microtrauma from lens wear providing a portal of bacterial entry through the otherwise-protective corneal epithelium) — a real, high-yield clinical association worth remembering precisely, since Pseudomonas keratitis in particular can progress with alarming speed to corneal perforation if not promptly, aggressively treated. Presentation includes eye pain, photophobia, decreased vision, and a visible corneal infiltrate/ulcer, often with an overlying hypopyon (a layered collection of inflammatory cells/pus in the anterior chamber, visible as a horizontal fluid level) in more severe cases — this hypopyon finding is a genuinely important, specifically testable sign of significant intraocular inflammatory involvement.

Bacterial Uveitis

Uveitis (inflammation of the uveal tract) is, genuinely worth remembering, more often non-infectious/autoimmune in overall aetiology (a real point distinguishing it from conjunctivitis and keratitis, which are predominantly infectious in cause) — but infectious causes, when present, include direct bacterial infection (comparatively uncommon as a primary cause) and, more commonly in the infectious-uveitis category, uveitis as a manifestation of a systemic infection with ocular involvement (tuberculosis, syphilis, and, in the appropriate epidemiological context, leptospirosis are all classically associated with uveitis as one of several possible systemic disease manifestations, directly connecting this topic back to Tuberculosis and Syphilis covered elsewhere in the curriculum). Presentation includes eye pain, photophobia, blurred vision, and, on slit-lamp examination, anterior chamber cells and flare — a specific ophthalmic examination finding reflecting active intraocular inflammation.

Diagnosis and Treatment — General Principles

Conjunctival/corneal scraping for Gram stain and culture is the diagnostic approach for suspected bacterial conjunctivitis or keratitis, particularly important for keratitis given its emergency status and the practical necessity of organism-directed rather than purely empirical therapy. Topical antibiotics (broad-spectrum initially, then narrowed per culture results) form the treatment backbone for conjunctivitis and keratitis, with keratitis specifically often requiring fortified (higher-concentration, compounded) topical antibiotic formulations given the need for genuinely high local drug concentrations to penetrate and treat corneal tissue effectively — a real, specifically testable point of contrast with the standard-concentration topical antibiotics generally sufficient for conjunctivitis alone. Uveitis management depends substantially on identifying and treating any underlying systemic infectious cause where present, alongside topical/systemic anti-inflammatory (corticosteroid) therapy where appropriate for the inflammatory component itself.