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Approach to the Critical Patient
Triage and time-critical risks
Vision-threatening priorities
Rapid ophthalmology involvement for suspected infectious keratitis
If central ulcer
If large infiltrate
If hypopyon
If marked vision reduction
Immediate escalation for perforation risk
If Seidel positive
If stromal melt
Immediate safety checks
Contact lens removal
Lens saved in sterile container for possible culture
Topical anesthetic limited to exam only
No outpatient topical anesthetic due to corneal toxicity risk
Hemodynamic and systemic instability screen
Sepsis concern
If fever
If immunocompromised with systemic symptoms
Key Concepts
Core framing
Corneal ulcer as stromal infiltrate with epithelial defect
High risk of rapid scarring in visual axis
Risk of corneal thinning and perforation
Microbial keratitis as ophthalmic emergency
Time-to-therapy linked to visual outcomes
Working diagnosis labels for coding
ICD-10 corneal ulcer
H16.0
H16.00
SNOMED CT concepts
Corneal ulcer
Infectious keratitis
Immediate decision points
Endophthalmitis concern
Severe pain out of proportion
Vitritis concern
Marked vision loss
Recent intraocular surgery or injection
Emergent ophthalmology
Orbital cellulitis concern
Pain with eye movements
Proptosis
Restricted extraocular movements
Open globe concern
Penetrating trauma history
Misshapen pupil
Shallow anterior chamber
Seidel positive
History
Symptom pattern and timeline
Presentation profile
Eye pain
Rapid onset over hours to days
Foreign body sensation
Photophobia
Worse with consensual light
Vision change
Blurry vision
Central haze
Discharge
Purulent
Watery
Progression and prior therapy
Prior topical antibiotics
Nonresponse after 24 to 48 hours
Prior topical steroids
Worsening after steroid exposure
Exposure and risk profile
Contact lens risks
Overnight wear
Pseudomonas risk
Water exposure with lenses
Swimming
Hot tub
Showering
Poor lens hygiene
Old solution reuse
Case contamination
Trauma and surface disease
Corneal abrasion preceding symptoms
Vegetative matter exposure
Soil exposure
Ocular surface disease
Dry eye
Blepharitis
Lagophthalmos
Infectious and immune risks
Immunosuppression
Diabetes mellitus
Systemic steroids
Chemotherapy
Herpetic eye disease history
Prior dendritic ulcers
Medication and allergy context
Fluoroquinolone allergy
Alternative regimen planning
Pregnancy and lactation
Medication selection considerations
Pitfalls
Diagnostic traps
Mislabeling as conjunctivitis
Delay in slit lamp and fluorescein evaluation
Patching
Worsening infection risk
Outpatient steroid initiation without ophthalmology
Risk of corneal melt and progression
Physical Exam
Vision and basic ocular exam
Visual function baseline
Visual acuity each eye
Pinhole acuity when available
Pupils
Relative afferent pupillary defect
External and motility
Eyelids and lash line
Blepharitis
Trichiasis
Extraocular movements
Pain with movement
Restriction pattern
Intraocular pressure
Avoid tonometry if open globe concern
Defer to ophthalmology
Slit lamp and fluorescein findings
Corneal findings
Epithelial defect with fluorescein uptake
Size in mm
Location relative to visual axis
Stromal infiltrate
Border quality
Depth
Satellite lesions
Corneal edema
Haze level
Anterior chamber
Cell and flare
Hypopyon presence and height
Iris abnormalities
Posterior synechiae
Seidel test
Aqueous leak
Perforation risk pathway
Herpetic patterns
Dendritic lesions
Terminal bulbs
Geographic ulcer pattern
Steroid exposure association
Red flags
High-risk exam features
Central ulcer
Visual axis involvement
Infiltrate size greater than 2 mm
Aggressive course likelihood
Stromal melting
Impending perforation
Hypopyon
Severe infection marker
Marked vision reduction
Endophthalmitis consideration
Differential Diagnosis
Infectious causes
Bacterial keratitis
Contact lens associated
Pseudomonas aeruginosa
Post-trauma
Staphylococcus species
Streptococcus species
Herpes simplex keratitis
Dendritic epithelial keratitis
Reduced corneal sensation
Varicella zoster keratitis
Dermatomal rash history
Pseudodendrites
Fungal keratitis
Vegetative matter trauma
Filamentous fungi
Chronic indolent course
Feathery borders
Acanthamoeba keratitis
Water exposure with contact lenses
Pain out of proportion
Ring infiltrate
Noninfectious mimics
Sterile contact lens infiltrate
Minimal pain
Peripheral infiltrate
Corneal abrasion without ulcer
Fluorescein uptake without stromal infiltrate
Rapid symptom improvement expectation
Anterior uveitis
Consensual photophobia
No corneal epithelial defect
Acute angle closure glaucoma
Headache and nausea
Mid-dilated pupil
Diffuse corneal edema
Chemical keratitis
Chemical exposure
Limbal ischemia risk
Laboratory Tests
Ocular microbiology
Corneal sampling indications
Smear and culture when high risk features present
Central location
Large size
Deep stromal involvement
Stromal melting
Atypical appearance
Poor response to empiric therapy
Bacterial studies
Gram stain
Rapid organism class guidance
Aerobic culture and sensitivities
Targeted therapy adjustment
Fungal studies
KOH wet mount
Filament detection
Fungal culture
Prolonged incubation needs
Acanthamoeba studies
Culture on non-nutrient agar with E coli overlay
Specialty lab coordination
Confocal microscopy access pathways
Ophthalmology-directed
Systemic tests when indicated
Immunocompromise evaluation
Glucose for diabetes concern
Poor healing risk context
HIV testing when risk factors present
Opportunistic infection context
Sepsis workup when systemic illness
Blood cultures if febrile and ill
Admission pathway support
Diagnostic Tests
Scoring Systems
Severity stratification for escalation
Location risk tiering
Central or paracentral as high risk
Peripheral as lower risk
Size tiering
Greater than 2 mm as high risk
2 mm or less as lower risk
Depth tiering
Deep stromal involvement as high risk
Superficial as lower risk
Anterior chamber reaction tiering
Hypopyon as high risk
None as lower risk
MRI
Indications
Suspected cavernous sinus complication
Cranial neuropathies
Severe headache with ocular findings
Orbital apex syndrome concern
Vision loss with ophthalmoplegia
Limitations
Low yield for isolated corneal ulcer
Not first-line for keratitis
CT
Indications
Orbital cellulitis concern
Proptosis
Pain with eye movements
Restricted motility
Intraorbital foreign body concern
High-velocity mechanism
Protocol considerations
CT orbits with contrast for cellulitis assessment
Abscess evaluation support
Limitations
Limited corneal detail
Not diagnostic for ulcer depth
Ultrasound
Ocular point-of-care ultrasound roles
B-scan when posterior segment view limited
Endophthalmitis concern
Retinal detachment concern
Contraindications
Avoid if open globe suspected
Interpretation pearls
Vitreous debris
Endophthalmitis support
Retinal flap
Detachment support
Disposition
Ophthalmology coordination
Same-day ophthalmology evaluation triggers
Central ulcer
Visual axis involvement
Infiltrate size greater than 2 mm
Culture consideration
Hypopyon
Severe infection marker
Stromal thinning or melt
Perforation risk
Contact lens related ulcer
Pseudomonas coverage priority
Transfer criteria
No local ophthalmology availability
Vision-threatening features present
Need for fortified antibiotics compounding access
Severe ulcer pathway
Admission versus outpatient
Admission criteria
Impending perforation
Seidel positive
Rapid stromal melt
Severe pain with inability to self-administer drops
Hourly therapy requirement
Immunocompromised with severe ulcer
High complication risk
Concern for endophthalmitis
Emergent intravitreal therapy pathway
Outpatient criteria
Small peripheral ulcer
No hypopyon
Minimal vision impact
Reliable hourly drop administration
Close follow-up within 24 hours
Treatment
Empiric antibacterial therapy
Initial regimen selection by severity
Mild to moderate suspected bacterial keratitis
Fourth-generation fluoroquinolone monotherapy
Moxifloxacin 0.5% ophthalmic
Initiate 1 drop every 1 hour while awake
If severe pain or high-risk features, initiate every 1 hour around the clock
Gatifloxacin 0.5% ophthalmic
Initiate 1 drop every 1 hour while awake
If high risk, initiate every 1 hour around the clock
Severe ulcer or sight-threatening features
Fortified dual therapy
Fortified tobramycin ophthalmic 14 mg/mL
Initiate 1 drop every 1 hour alternating with second agent
If fulminant, loading dose every 5 to 15 minutes for 1 hour then hourly
Fortified cefazolin ophthalmic 50 mg/mL
Initiate 1 drop every 1 hour alternating with aminoglycoside
If gram negative concern, consider ceftazidime substitute per ophthalmology
MRSA risk or poor response
Fortified vancomycin ophthalmic per ophthalmology
Dosing typically hourly initially
Sensitivity-guided continuation
Evidence notes for antibiotic choices
Fluoroquinolone monotherapy and fortified combinations as common effective options
Comparative effectiveness differences small across many regimens
Time to healing varies by regimen in evidence synthesis
AAO Preferred Practice Pattern support for culture in high-risk ulcers
Targeted pathogen pathways
Herpes simplex keratitis suspicion
Antiviral therapy
Ganciclovir 0.15% gel
Initiate 1 drop 5 times daily
Taper per ophthalmology after epithelial healing
Acyclovir PO 400 mg
Initiate 5 times daily
Duration per ophthalmology
Steroid avoidance in epithelial HSV
Ophthalmology-directed only
Fungal keratitis suspicion
Natamycin 5% ophthalmic
Initiate 1 drop every 1 hour while awake
Prolonged course expectation
Voriconazole ophthalmic or PO per ophthalmology
Escalation when natamycin nonresponse
Acanthamoeba keratitis suspicion
Biguanide therapy per ophthalmology
PHMB 0.02%
Initiate hourly initially
Prolonged taper over months typical
Chlorhexidine 0.02%
Initiate hourly initially
Combination strategy common
Adjunctive therapy and comfort
Cycloplegia for pain and photophobia
Cyclopentolate 1% ophthalmic
Initiate 1 drop 2 to 3 times daily
Atropine 1% ophthalmic
Initiate 1 drop once to twice daily for severe spasm per ophthalmology
Systemic analgesia
Acetaminophen
Dosing per age and weight
NSAID oral if no contraindications
Avoid topical NSAID when epithelial defect large
Corneal melt mitigation adjuncts
Doxycycline PO 100 mg
Initiate twice daily when significant thinning or melt risk per ophthalmology
Vitamin C supplementation per ophthalmology
Collagen support rationale
Steroids and contraindications
Topical corticosteroids
Avoid initiation in ED without ophthalmology
Risk of worsening undiagnosed fungal or HSV disease
Adjunctive steroid evidence mixed
Requires specialist selection and timing
Contact lens precautions
No contact lens wear until ophthalmology clearance
Discard current lenses and case
Evidence levels and guideline framing
Guideline alignment
AAO Preferred Practice Pattern for bacterial keratitis as primary reference
ACEP Level C style consensus mapping for ED actions
Immediate topical antibiotic therapy for suspected microbial keratitis
Urgent ophthalmology for high-risk features
Class recommendation mapping
Class I
Immediate topical antimicrobial therapy when microbial keratitis suspected
Same-day ophthalmology for central or severe ulcers
Class IIa
Corneal cultures for high-risk ulcers before antibiotics when feasible without delay
Class IIb
Adjunctive systemic agents for melt risk per specialist
Special Populations
Pregnancy
Maternal and fetal considerations
Vision preservation priority
Same urgency for therapy and ophthalmology evaluation
Medication considerations
Prefer topical therapy due to low systemic absorption
Nasolacrimal occlusion technique to reduce systemic absorption
Antimicrobial selection notes
Fluoroquinolone ophthalmic typically acceptable when benefits outweigh risks
Tetracycline avoidance in pregnancy
Follow-up and monitoring
Same-day ophthalmology when high-risk features
Central ulcer
Hypopyon
Geriatric
Higher risk features
Ocular surface disease prevalence
Dry eye
Blepharitis
Immunosenescence
More severe infection risk
Medication safety
Systemic NSAID caution
Renal risk
GI bleeding risk
Polypharmacy review
Anticoagulant considerations for trauma history
Pediatrics
Pediatric-specific risks
Contact lens use in adolescents
Hygiene issues
Trauma and foreign body
Examination challenges
Dosing and administration feasibility
Caregiver ability for hourly drops
Lower threshold for admission
Sedation needs for corneal scraping
Specialist setting coordination
Safeguarding concerns
Non-accidental injury consideration when trauma history unclear
Documentation and safeguarding pathway
Background
Epidemiology
Disease burden
Infectious keratitis as leading cause of unilateral corneal blindness worldwide
Regional variation by contact lens use and agricultural trauma
Contact lens wear as major risk factor in high-income settings
Pseudomonas prominence in lens-associated cases
Pathophysiology
Mechanism
Epithelial barrier disruption
Microbial adherence and invasion
Stromal inflammation
Collagenolysis
Thinning and perforation risk
Organism-specific patterns
Bacterial
Rapid necrosis and suppuration
Fungal
Hyphal penetration
Feathery infiltrate edges
Acanthamoeba
Perineural inflammation
Pain out of proportion
Therapeutic Considerations
Treatment principles
Empiric broad coverage early
High local drug concentrations with topical dosing
Culture-directed narrowing when available
Resistance and atypical pathogen detection
Antibiotic strategy evidence
Fluoroquinolone monotherapy as common first-line for many cases
Similar cure rates compared with fortified regimens in multiple analyses
Fortified dual therapy for severe ulcers and resistant risk
Broader coverage and high concentration approach
Steroid timing and selection
Potential benefit for scarring reduction balanced against infection worsening risk
Specialist-led decisions
Patient Discharge Instructions
copy discharge instructions
Discharge instructions
Diagnosis
Corneal ulcer or suspected infectious keratitis
Medications
Use drops exactly as prescribed
Do not stop early even if better
Contact lenses
No contact lens wear until cleared
Discard current lenses and case
Eye care
No eye patch
No rubbing
Sunglasses for light sensitivity
Follow-up
Ophthalmology within 24 hours or same day as directed
Return sooner if unable to obtain drops or worsening symptoms
Return to ED now for
Worse vision
Increasing pain
Increasing redness or swelling
New headache with nausea or vomiting
New fever
Fluid leaking from the eye
New severe light sensitivity
References
Clinical guidelines and high-quality sources
Guideline sources
American Academy of Ophthalmology Preferred Practice Pattern
Bacterial Keratitis Preferred Practice Pattern 2024
AAO education summary page for bacterial keratitis PPP 2023
Evidence reviews
Cochrane review on topical antibiotics for bacterial keratitis 2025
Cochrane review on adjunctive topical corticosteroids for bacterial keratitis
Systematic reviews comparing fluoroquinolones and fortified antibiotics
Point-of-care references
StatPearls Bacterial Keratitis chapter updates on hourly dosing and escalation
EyeWiki Bacterial Keratitis overview and practice patterns
Internal system formatting and structure rules
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.