Corneal ulcer
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"corneal ulcer" OR "corneal infection"
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I now have thorough information from multiple textbooks. Here is the comprehensive clinical overview:
Corneal Ulcer
A corneal ulcer is a serious infection involving multiple layers of the cornea, developing secondary to a break in the epithelial barrier that allows infectious agents to invade the underlying stroma. It is the clinical end result of what is broadly called infectious (microbial) keratitis.
Definition
A corneal ulcer represents full-thickness epithelial loss with underlying stromal involvement and associated inflammatory infiltrate. It must be distinguished from a simple abrasion (epithelial loss only, no stromal involvement). The hallmark on slit-lamp is a focal white opacity (infiltrate) in the corneal stroma associated with an epithelial defect and underlying stromal thinning/tissue loss.
Pathogenesis
The initial disruption of the epithelium can occur via:
-
Desquamation (e.g., exposure keratitis from Bell's palsy, incomplete lid closure causing desiccation)
-
Trauma (direct inoculation of the cornea)
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Direct microbial invasion (notably Neisseria gonorrhoeae, N. meningitidis, C. diphtheriae, and H. influenzae can penetrate an intact epithelium)
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Contact lens wear - causes hypoxia, minor trauma, and direct bacterial adherence to the lens surface
-
Kanski's Clinical Ophthalmology, p. 211; Tintinalli's Emergency Medicine, p. (block 20)
Risk Factors
| Factor | Notes |
|---|---|
| Contact lens wear | Most important risk factor. Soft lenses > rigid gas permeable. Extended-wear dramatically increases risk. Pseudomonas causes >60% of contact lens-related keratitis |
| Trauma | Including refractive surgery (especially LASIK) |
| Ocular surface disease | Dry eye, bullous keratopathy, entropion |
| Immunosuppression | Topical or systemic steroids, systemic immunosuppressants |
| Previous ocular surgery | Penetrating keratoplasty, refractive surgery |
| Systemic disease | Diabetes, vitamin A deficiency, collagen vascular diseases |
Causative Organisms
Bacteria (most common cause overall)
- Pseudomonas aeruginosa - aggressive, accounts for >60% of contact lens-related keratitis
- Staphylococcus aureus - focal, fairly well-defined yellow-white infiltrate
- Streptococcus pneumoniae - often aggressive
- Moraxella species
- Serratia species
Viruses
- Herpes simplex virus (HSV) - may cause dendrites and stromal infiltrate
- Varicella zoster virus (VZV)
Fungi
- Candida - common in immunocompromised, often mimic bacterial ulcers
- Aspergillus, Fusarium, Penicillium, Acremonium - filamentous fungi; associated with vegetable/plant matter trauma and contact lens wear; feathery borders and satellite lesions on exam
Protozoa
-
Acanthamoeba - extremely painful, associated with soft contact lens wear, swimming/hot tub exposure; perineural invasion; late ring-shaped infiltrate
-
Tintinalli's Emergency Medicine, Table 241-5; Wills Eye Manual, Section 4.11; Kanski's Clinical Ophthalmology, p. 211
Clinical Features
Symptoms
- Red eye (moderate to severe)
- Moderate-to-severe ocular pain or foreign body sensation
- Photophobia (consensual photophobia if associated iritis)
- Decreased vision (especially if central ulcer)
- Mucopurulent discharge
- Acute contact lens intolerance
Signs
On slit-lamp examination (critical findings):
- Focal white/grey stromal infiltrate with overlying epithelial defect
- Heaped-up ulcer edges (vs. cleaner edges in a simple abrasion)
- Stromal edema and Descemet membrane folds
- Anterior chamber reaction (flare and cells)
- Hypopyon (sterile inflammatory cells in anterior chamber) - sign of severe keratitis
- Conjunctival injection (usually diffuse)
- Mucopurulent discharge, upper eyelid edema
Severe cases may also show:
- Posterior synechiae
- Hyphaema
- Elevated IOP
- Corneal perforation (a feared complication)
Note: A slit beam cannot see clearly through an infiltrate or ulcer to the iris, whereas stromal edema or mild scars are more transparent - this helps distinguish depth of involvement.
- Wills Eye Manual, p. 199-202
Organism-Specific Clues
| Organism | Clinical Clue |
|---|---|
| Pseudomonas | Contact lens wearer; aggressive, rapidly progressive; liquefactive necrosis; mucopurulent discharge |
| Staphylococcus | Focal, well-defined yellow-white infiltrate; often associated with blepharitis |
| Streptococcus | Often aggressive; hypopyon common |
| Fungi (filamentous) | Vegetable matter trauma; feathery borders; satellite lesions |
| Candida | Immunocompromised, preexisting ocular surface disease |
| HSV | Eyelid vesicles, dendrites; recurrent unilateral disease |
| Acanthamoeba | Extremely painful; contact lens + water exposure; ring-shaped infiltrate late; perineural invasion |
Differential Diagnosis
- Corneal abrasion - epithelial defect only, no stromal infiltrate, no white opacity
- Sterile corneal infiltrate - immune reaction to contact lens solution/hypoxia; multiple small peripheral lesions, little staining, minimal AC reaction
- Staphylococcal hypersensitivity - peripheral, often bilateral, clear space between infiltrate and limbus, localized injection, no/minimal AC reaction
- HSV stromal keratitis - no/poor response to antibiotics, dendrites, history of herpes
- Fungal keratitis - feathery borders, satellite lesions, must be considered after vegetable trauma
- Topical anesthetic abuse - large ring opacity, should be suspected with poor response to therapy
- Peripheral corneal thinning/melting - associated systemic disease (RA, Wegener's, PAN)
Investigations
Corneal culture (mandatory before starting antibiotics):
The ophthalmologist scrapes the center of the ulcer to culture the offending organism. Culture media used:
| Medium | Organisms Detected |
|---|---|
| Blood agar | Most bacteria and fungi (except Neisseria, Haemophilus, Moraxella) |
| Chocolate agar | Fastidious bacteria (H. influenzae, Neisseria, Moraxella) |
| Sabouraud dextrose agar | Fungi |
| Non-nutrient agar + E. coli | Acanthamoeba |
| Brain-heart infusion broth | Streptococci, meningococci, yeasts |
| Lowenstein-Jensen | Mycobacteria, Nocardia (keep for 8 weeks) |
PCR + nanopore sequencing is now available and can identify the exact species and antibiotic resistance profile.
- Kanski's Clinical Ophthalmology, Table 7.2, p. 229
Treatment
General Principles
- Treat aggressively - do not delay
- Obtain cultures before starting antibiotics
- Emergent ophthalmologic consultation is indicated
- Never pressure patch an infected eye; never patch a contact lens wearer
Topical Antibiotics (first-line)
Fluoroquinolones are the current standard:
- Ciprofloxacin (Ciloxan) or Ofloxacin (Ocuflox) - 1 drop every hour in the affected eye
- Moxifloxacin or Gatifloxacin are also commonly used (good Gram-positive and Gram-negative coverage)
For severe/sight-threatening ulcers - loading dose protocol:
1 drop every 5 minutes for five doses, then every 30-60 minutes around the clock
Adjunctive Measures
- Cycloplegic (e.g., cyclopentolate 1% TID) - for iritis/ciliary spasm
- Topical steroids - only after organism and sensitivities known, infection under control, and severe inflammation persists; avoid in fungal, atypical mycobacteria, Nocardia, or Pseudomonas keratitis
- Doxycycline 100 mg PO BID (MMP inhibitor) + Vitamin C 1-2 g/day - to suppress connective tissue breakdown and prevent perforation in thinning corneas
- Eye shield (not pressure patch) for corneal thinning
- No contact lens wear
Systemic Antibiotics
- Oral fluoroquinolones (ciprofloxacin 500 mg BID; moxifloxacin 400 mg daily) for scleral extension or impending/frank perforation
- Ceftriaxone 1 g IV q12-24h for N. gonorrhoeae with corneal involvement (single 1 g IM if conjunctival involvement only)
- Amoxicillin/clavulanate for H. influenzae infections (risk of systemic spread)
- Note: systemic fluoroquinolones are no longer recommended for gonococcal infections due to resistance
Indications for Hospitalization
-
Sight-threatening infection or impending perforation
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Patient unable to administer drops at required frequency
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Likely noncompliance
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Suspected topical anesthetic abuse
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Neisseria infection (requiring IV antibiotics)
-
Wills Eye Manual, p. 199-207; Tintinalli's Emergency Medicine, block 20
Complications
- Corneal scarring - permanent visual impairment
- Corneal perforation - may lead to endophthalmitis
- Endophthalmitis - fulminant, sight-threatening
- Descemetocele - Descemet membrane bulging through a full-thickness ulcer
- Adherent leucoma - iris adherent to posterior cornea
- Corneal vascularization
- Phthisis bulbi - end-stage shrinking of globe after severe infection
Recent Evidence (2024-2026)
A Cochrane network meta-analysis (2025) on topical antibiotics for bacterial keratitis is the most current high-level evidence available (PMID: 40728038). A 2024 systematic review of Fusarium keratitis (1969-2023, PMID: 39107598) highlights the growing importance of fungal corneal infections.
Sources: Tintinalli's Emergency Medicine (A Comprehensive Study Guide); The Wills Eye Manual (9th ed); Kanski's Clinical Ophthalmology (10th ed); Rosen's Emergency Medicine
Give in short
Corneal Ulcer - Quick Summary
Definition
Full-thickness epithelial loss + stromal infiltration/tissue loss. More serious than a simple abrasion.
Key Risk Factors
- Contact lens wear (especially extended-wear soft lenses) - #1 risk
- Trauma / ocular surgery
- Immunosuppression (topical/systemic steroids)
- Exposure keratitis (Bell's palsy)
Common Organisms
| Type | Examples |
|---|---|
| Bacteria | Pseudomonas (contact lens), S. aureus, S. pneumoniae |
| Virus | HSV, VZV |
| Fungi | Candida, Aspergillus, Fusarium |
| Protozoa | Acanthamoeba (contact lens + water exposure) |
Clinical Features
- Symptoms: Red eye, severe pain, photophobia, decreased vision, discharge
- Signs: White/grey stromal infiltrate, epithelial defect, hypopyon (severe), AC reaction
Diagnosis
- Slit-lamp exam (corneal scraping for culture before starting antibiotics)
Treatment
- Topical fluoroquinolone (ciprofloxacin/moxifloxacin) - 1 drop/hour; q5min loading for severe cases
- Cycloplegic for iritis
- Systemic antibiotics for Neisseria (ceftriaxone IV) or scleral extension
- No patching, no contact lenses
- Urgent ophthalmology referral
Complications
Corneal scarring → perforation → endophthalmitis → vision loss
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