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This is a clinician-written, evidence-based summary aligned to the USMLE Step 2 CK Content Outline. It is intended for medical students preparing for USMLE Step 2 CK. Management reflects current ACC/AHA, USPSTF, and APA guidelines. Always cross-reference with UpToDate, institutional protocols, and clinical judgment.
The Bottom Line
- Corneal abrasion causes acute pain, tearing, photophobia, and foreign body sensation after trauma or contact lens use
- Fluorescein staining shows epithelial defect; vertical linear abrasions suggest retained foreign body under the eyelid
- Contact lens-related corneal defects require antipseudomonal coverage and careful follow-up
- Corneal ulcer/keratitis: corneal infiltrate or opacity plus epithelial defect — urgent ophthalmology
- Do not prescribe topical anesthetics for home use; they delay healing and can cause severe keratopathy
Overview
A corneal abrasion is a defect in the corneal epithelium, most often from fingernail trauma, foreign body, contact lens wear, or dry eye. A corneal ulcer is an epithelial defect with stromal inflammation/infiltrate, usually infectious keratitis. The clinical distinction matters because uncomplicated abrasions usually heal within 24-72 hours, whereas microbial keratitis can rapidly scar, thin, or perforate the cornea. Contact lens wear is the major Step 2 CK risk factor for Pseudomonas keratitis.
Epidemiology
Corneal abrasions are common in emergency and primary care. Infectious keratitis is less common but vision-threatening. Risk factors for corneal ulcer include contact lens wear, overnight lens use, poor lens hygiene, ocular surface disease, trauma with vegetative matter, immunosuppression, topical steroid use, prior HSV keratitis, and neurotrophic cornea. Contact lens-related microbial keratitis is often bacterial and classically associated with Pseudomonas.
Clinical Features
Symptoms
Severe foreign body sensation, sharp pain, tearing, and photophobia
History of fingernail injury, foreign body, contact lens wear, welding/UV exposure, or vegetative trauma
Blurred vision if central defect, edema, or ulcer
Contact lens use with pain and photophobia is a red flag for microbial keratitis
Dendritic pain/redness history or recurrent episodes suggest HSV keratitis
Signs
Fluorescein uptake at epithelial defect under cobalt blue light
Conjunctival injection and blepharospasm
Corneal opacity/infiltrate, hypopyon, or stromal haze suggests corneal ulcer/keratitis
Vertical linear abrasions suggest retained foreign body under upper eyelid
Branching dendritic lesion with terminal bulbs suggests HSV epithelial keratitis
Positive Seidel test suggests globe leak/perforation
Investigations
First-line
Visual acuityMust be documented before treatment; decreased acuity is a red flag for central lesion, ulcer, edema, or deeper injury
Fluorescein stainingIdentifies epithelial defect; perform Seidel test when penetrating injury is possible
Eyelid eversionLook for retained subtarsal foreign body, especially with vertical abrasions or persistent symptoms
Second-line
Slit-lamp examinationAssesses infiltrate, anterior chamber reaction, foreign body, rust ring, ulcer depth, and hypopyon
Corneal culture/scrapingFor large, central, deep, atypical, sight-threatening, contact lens-associated, immunocompromised, or nonresponsive ulcers
Herpes testingUsually clinical; consider when dendritic lesions, recurrent disease, or atypical keratitis occurs
Specialist
Ophthalmology evaluationUrgent for ulcer/infiltrate, contact lens keratitis concern, decreased vision, penetrating injury, hypopyon, HSV, or non-healing abrasion
1
Simple corneal abrasion
- Remove foreign body if superficial and safe; evert lid to remove retained debris
- Topical antibiotic prophylaxis: erythromycin ointment or polymyxin B/trimethoprim drops for non-contact lens abrasions
- Pain control with oral NSAIDs/acetaminophen; topical NSAID drops may be used briefly in selected patients
- Cycloplegic drops may help severe photophobia/ciliary spasm but are not needed for most small abrasions
- Avoid eye patching in most cases, especially contact lens-related abrasions
2
Contact lens-related abrasion
- Stop contact lens use immediately and discard lenses/case
- Use antipseudomonal topical antibiotic, commonly a fluoroquinolone such as ciprofloxacin, ofloxacin, levofloxacin, or moxifloxacin
- Recheck within 24 hours or refer if pain, photophobia, infiltrate, or decreased vision
3
Corneal ulcer / bacterial keratitis
- Urgent ophthalmology; culture if central, large, deep, atypical, or vision-threatening
- Frequent fortified topical antibiotics or fluoroquinolone monotherapy depending on size, severity, and specialist guidance
- Do not use topical steroids unless prescribed by ophthalmology after appropriate antimicrobial therapy
4
Contraindications and safety
- Do NOT prescribe topical anesthetics for home use
- Avoid topical corticosteroids in suspected HSV epithelial keratitis, fungal keratitis, or undifferentiated corneal ulcer
- Suspected open globe: shield the eye, avoid pressure/ultrasound/tonometry, give systemic antibiotics, and urgent surgery evaluation
Complications
- Corneal ulcer: Infectious keratitis with stromal involvement and scarring risk
- Corneal perforation: Emergency, especially with severe bacterial/fungal keratitis or topical anesthetic abuse
- Permanent corneal scar: Central scar causes irregular astigmatism and reduced vision
- Recurrent corneal erosion: Recurrent pain on waking after prior abrasion
- Endophthalmitis: Rare but devastating if infection penetrates intraocularly
USMLE Step 2 CK Exam Tips
- 1Painful red eye + foreign body sensation + fluorescein uptake = corneal abrasion
- 2Vertical linear fluorescein scratches = retained foreign body under upper eyelid — evert the lid
- 3Contact lens wearer = cover Pseudomonas with topical fluoroquinolone
- 4Corneal opacity/infiltrate + epithelial defect = corneal ulcer/keratitis — urgent ophthalmology
- 5Never give topical anesthetics for outpatient use
- 6Dendritic fluorescein lesion = HSV keratitis; avoid topical steroids and treat with antivirals
- 7Seidel-positive wound = open globe; shield, no pressure, urgent ophthalmology
- 8Patching is generally not recommended and is contraindicated in contact lens abrasions
practicetest your knowledge on corneal abrasion & ulcerApply what you've learnt with USMLE Step 2 CK-style questions from the iatroX Q-Bank — ophthalmology and beyond.
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